Dentification and correction of the lead-time bias and length bias in cancer screening studies / 中华预防医学杂志

Lead-time bias and length bias were common systematic errors in observational screening studies, which might be a common cause of overstating or distorting the true screening effects. One of key concerns in observational screening studies was how to estimate the screening effects based on the consideration of these two biases. This paper illustrated how to identify and correct the lead-time bias using the tumor volume doubling time and the non-homogeneous Poisson process, and how to correct the length bias using a weighted method. The application conditions of each method were also discussed to present several useful toolboxes to correct the lead-time bias and length bias appropriately and evaluate the effectiveness of the cancer screening program accurately.

Reporting of statistical regression analyses in Biomédica: A critical assessment review / Reporte estadístico en los análisis de regresión en Biomédica: una revisión y evaluación crítica

ABSTRACT Introduction: Regression modeling is a statistical method commonly used in health research, especially by observational studies. Objective: The objectives of this paper were to 1) determine the frequency of reporting of regression modeling in original biomedical and public health articles that were published in Biomédica between 2000 and 2017; 2) describe the parameters used in the statistical models, and 3) describe the quality of the information reported by the studies to explain the statistical analyses. Materials and methods: We conducted a critical assessment review of all original articles published in Biomédica between 2000 and 2017 that used regression models for the statistical analysis of the studies main objectives. We generated a 20-item checklist based on four good practice guidelines for the presentation of statistical methods. Results: Most of the studies were observational studies related to public health sciences (65.7%). Less than half (37.2%) of them reported using a combination of conceptual frameworks and statistical criteria for the selection of variables to be included in the regression model. Less than one quarter (22.1%) reported the verification of the assumptions of the model. The most frequently used uncertainty measure was the p-value (73.5%). Conclusion: There are significant limitations in the quality of the reports of statistical regression models, which reviewers and readers need in order to correctly assess and interpret the statistical models. The results, herein, are provided as an invitation to researchers, reviewers, and editors of biomedical journals to develop, promote, and control an appropriate culture for statistical analysis and reporting in Colombia.

RESUMEN Introducción. Los modelos de regresión son métodos estadísticos comúnmente utilizados en la investigación en salud, especialmente en estudios observacionales. Objetivos. Determinar la frecuencia de uso de modelos de regresión en los artículos originales de biomedicina y salud pública publicados en Biomédica entre 2000 y 2017, describir los parámetros utilizados en los modelos estadísticos, así como la calidad de la información reportada por los estudios para explicar el análisis estadístico. Materiales y métodos. Se hizo una revisión y evaluación crítica de todos los artículos originales publicados en la revista Biomédica entre 2000 y 2017 que utilizaron modelos de regresión en el análisis estadístico. Se construyó una lista de verificación de 20 ítems sobre la base de cuatro guías de buenas prácticas para la presentación de los métodos estadísticos. Resultados. La mayoría de los estudios incluidos eran estudios observacionales relacionados con las ciencias de la salud pública (65,7 %). En menos de la mitad (37,2 %) de ellos se informó sobre el uso de una combinación de marco conceptual y criterios estadísticos para la selección de las variables incluidas en el modelo de regresión; en menos de una cuarta parte (22,1 %) se informó de la verificación de los supuestos del modelo, y la medida de incertidumbre reportada con mayor frecuencia fue el valor de p (73,5 %). Conclusión. Hay limitaciones importantes en la calidad de los informes de los modelos de regresión estadísticos necesarios para la correcta evaluación y la interpretación de los modelos estadísticos por parte de los revisores y lectores. Los resultados se ofrecen como una invitación a investigadores, revisores y editores de revistas biomédicas a que promuevan el desarrollo de una cultura adecuada de análisis estadístico y presentación de informes en Colombia.

Validez de constructo y consistencia interna de tres estructuras factoriales y dos sistemas de puntuación del cuestionario de salud general de 12 ítems / Construct validity and internal consistency of three factor structures and two scoring methods of the 12-item General Health Questionnaire

Resumen Introducción: El análisis de las propiedades psicométricas de un instrumento reviste importancia para el control de sesgos en la medición. Objetivo: Comparar la validez de constructo y la consistencia interna de tres estructuras factoriales del cuestionario de salud general de 12 ítems. Materiales y métodos: Se hizo un estudio de validación en una muestra anidada de 483 estudiantes de odontología de Cartagena, Colombia. Además de las preguntas del instrumento, se hicieron otras sobre aspectos personales. Se evaluó la validez de constructo de la estructura unidimensional, de la unidimensional con corrección del sesgo de respuesta, y de la de dos y tres factores y sistemas de puntuación del tipo de la escala de Likert (0-1-2-3) y dicotómico (0-0-1-1). La validez se determinó con un análisis factorial confirmatorio y, la consistencia interna, con el coeficiente alfa de Cronbach para la escala de Likert y la fórmula 20 de Kuder-Richardson para el método dicotómico empleando los programas Stata(tm), versión 13.2 (Stata Corp, USA) y Mplus(tm), versión 7.11 (Muthen andMuthen, USA). Resultados: Los índices de ajuste revelaron que el mejor modelo era el unidimensional con corrección del sesgo de respuesta y puntación dicotómica (grados de libertad=36; ji al cuadrado=52,432; raíz cuadrada del error medio de aproximación=0,03; IC90% 0,008-0,048; índice comparativo de ajuste=0,982; índice de Tucker-Lewis=0,966). La consistencia interna fue de 0,70. Conclusiones: El ajuste del modelo obtenido en este estudio permitió controlar el sesgo de medición y, así, garantizar la validez externade los resultados del cuestionario de salud general de 12 ítems para la evaluación de las condiciones mentales en esta población. Las propiedades psicométricas de las escalas deben evaluarse críticamente antes del análisis de los resultados.

Abstract Introduction: The analysis of the psychometric properties of an instrument is important for the control of measurement bias. Objective: To compare the construct validity and internal consistency of three factorial structures of the General Health Questionnaire-12. Materials and methods: We conducted a validation study in a nested sample of 483 dentistry students from Cartagena, Colombia. The instrument was applied along with questions about personal factors. The construct validity of the following structures was evaluated: one-dimensional, one-dimensional with correction of response bias, and the two and three-factor structure, and these scoring systems: Likert scale (0-1-2-3) and dichotomous (0-0-1-1) scoring method. Validity was determined by confirmatory factorial analysis, and the internal consistency with Cronbach's alpha coefficient for the Likert scale and the Kuder-Richardson Formula 20 for the dichotomous scoring using the Stata(tm), v. 13.2 (Stata Corp, USA) and Mplus(tm), v.7.11 (Muthen and Muthen, USA) software. Results: Adjustment indexes revealed that the best model was the one-dimensional one with correction of response bias based on a dichotomous scoring (degrees of freedom=36; chi square=52.432; root mean square error of approximation=0.03; 90% CI: 0.008-0.048; comparative fit index=0.982; Tucker-Lewis index=0.966). The internal consistency was 0.70. Conclusions: The adjustment of the model in this study allowed for the control of measurement bias and guaranteed external validity of results when using the General Health Questionnaire-12 to evaluate mental conditions in this population. The psychometric properties of the scales should be critically evaluated before results analysis.

How to avoid bias in systematic reviews of observational studies / Como minimizar vieses em revisões sistemáticas de estudos observacionais

ABSTRACT Although systematic reviews have numerous advantages, they are vulnerable to biases that can mask the true results of the study and therefore should be interpreted with caution. This article aims at critically reviewing the literature about systematic reviews of observational studies, emphasizing the errors that can affect this type of study design and possible strategies to overcome these errors. This is an integrative literature review whose search was conducted in the databases States National Library of Medicine, Scientific Electronic Library Online and Google Scholar. The following descriptors were used: review, bias (epidemiology) and observational studies as the subject, including relevant books and documents which were consulted. Data collection was conducted between June and July 2016. The most known errors present in the design of systematic reviews were those related to the selection and publication. Although this type of study is subject to possible errors, preventive measures used during the planning of systematic reviews and even during and after their implementation can help ensure scientific rigor. This literature can serve as an important tool for the development and interpretation of systematic reviews of observational studies.

RESUMO Embora as revisões sistemáticas tenham inúmeras vantagens, eles são vulneráveis a vieses que podem mascarar os verdadeiros resultados do estudo e, portanto, devem ser interpretados com cautela. A proposta deste artigo é revisar criticamente a literatura acerca das revisões sistemáticas de estudos observacionais, enfatizando os erros que podem afetar este tipo de desenho de estudo e as possíveis estratégias para superar esses erros. Trata-se de uma revisão integrativa da literatura. A pesquisa bibliográfica foi conduzida nas bases de dados: States National Library of Medicine, Scientific Electronic Library Online, e Google Scholar. Para a busca em bases de dados foram utilizados os descritores: revisão, viés (epidemiologia) e estudos observacionais como assunto. Também foram consultados livros e documentos com relevância para o tema. A coleta dos dados foi realizada entre junho e julho de 2016. Os erros mais conhecidos, presentes no delineamento de revisões sistemáticas, foram os relacionados com a seleção e publicação. Embora este tipo de estudo esteja sujeito a possíveis erros, as medidas preventivas postas em prática durante o planejamento de revisões sistemáticas e até mesmo durante e após a sua execução podem ajudar a garantir o rigor científico. Esta revisão da literatura pode servir como um instrumento importante para o desenvolvimento e interpretação de revisões sistemáticas de estudos observacionais.

Multimorbilidad: bases conceptuales, modelos epidemiológicos y retos de su medición / Multimorbidity: conceptual basis, epidemiological models and measurement challenges

El incremento continuo de pacientes con perfiles clínicos complejos debidos a enfermedades crónicas ha favorecido el uso cada vez más extendido del término multimorbilidad. Es indispensable disponer de una medición apropiada de esta condición, dado que representa un reto para el manejo clínico de los pacientes, los sistemas de salud y la investigación epidemiológica. En este ensayo se revisan las propuestas conceptuales subyacentes a la medición de la multimorbilidad y se discuten los retos metodológicos involucrados, tomando como referencia las definiciones clásicas de comorbilidad, sus diferencias con el concepto de multimorbilidad y su papel en los estudios epidemiológicos, así como los distintos modelos conceptuales de los que se derivan las definiciones operativas y las estrategias de medición de dicha variable. Se pudo determinar que hay una brecha importante entre el desarrollo del concepto de multimorbilidad y las definiciones operativas, a pesar del significativo avance teórico que ha permitido trascender la concepción clásica de comorbilidad para llegar al concepto actual de multimorbilidad. Sin embargo, las estrategias de medición no se han desarrollado al mismo ritmo del concepto, por lo que se requieren nuevas propuestas metodológicas que permitan obtener información sobre su verdadero impacto en la salud de las personas y sus implicaciones para la salud pública.

The growing number of patients with complex clinical profiles related to chronic diseases has contributed to the increasingly widespread use of the term ´multimorbidity´. A suitable measurement of this condition is essential to epidemiological studies considering that it represents a challenge for the clinical management of patients as well as for health systems and epidemiological investigations. In this context, the present essay reviews the conceptual proposals behind the measurement of multimorbidity including the epidemiological and methodological challenges it involves. We discuss classical definitions of comorbidity, how they differ from the concept of multimorbidity, and their roles in epidemiological studies. The various conceptual models that contribute to the operational definitions and strategies to measure this variable are also presented. The discussion enabled us to identify a significant gap between the modern conceptual development of multimorbidity and the operational definitions. This gap exists despite the theoretical developments that have occurred in the classical concept of comorbidity to arrive to the modern and multidimensional conception of multimorbidty. Measurement strategies, however, have not kept pace with this advance. Therefore, new methodological proposals need to be developed in order to obtain information regarding the actual impact on individuals´ health and its implications for public health.

Utilização de diagramas causais em epidemiologia: um exemplo de aplicação em situação de confusão / Use of causal diagrams in Epidemiology: application to a situation with confounding / Utilización de diagramas causales en epidemiología: un ejemplo de su aplicación en situación de confusión

Resumo: Apesar do crescente reconhecimento de seu potencial, os diagramas causais ainda são pouco utilizados na investigação epidemiológica. Uma das possíveis razões é que muitos programas de investigação envolvem temas sobre o qual há certo grau de incerteza sobre os mecanismos dos processos que geram os dados. Neste trabalho, a relação entre estresse ocupacional e obesidade é utilizada como um exemplo de aplicação de diagramas causais em questões relacionadas ao confundimento. São apresentadas etapas da seleção de variáveis para ajuste estatístico e da derivação das implicações estatísticas de um diagrama causal. A principal vantagem dos diagramas causais é tornar explícitas as hipóteses adjacentes ao modelo considerado, permitindo que suas implicações possam ser analisadas criticamente, facilitando, dessa forma, a identificação de possíveis fontes de viés e incerteza nos resultados de um estudo epidemiológico.

Abstract: Epidemiological research still rarely uses causal diagrams, despite growing recognition of their explanatory potential. One possible reason is that many research programs involve themes in which there is a certain degree of uncertainty as to mechanisms in the processes that generate the data. In this study, the relationship between occupational stress and obesity is used as an example of the application of causal diagrams to questions related to confounding. The article presents the selection stages for variables in statistical adjustment and the derivation of a causal diagram's statistical implications. The main advantage of causal diagrams is that they explicitly reveal the respective model's underlying hypotheses, allowing critical analysis of the implications and thereby facilitating identification of sources of bias and uncertainty in the epidemiological study's results.

Resumen: A pesar del creciente reconocimiento de su potencial, los diagramas causales todavía se utilizan poco en la investigación epidemiológica. Una de las posibles razones es que muchos programas de investigación están involucrados en temas sobre los cuales existe un cierto grado de incertidumbre acerca de los mecanismos de los procesos que generan los datos. En este trabajo, la relación entre estrés ocupacional y obesidad se utiliza como un ejemplo de aplicación de diagramas causales en cuestiones relacionadas con la confusión. Se presentan etapas de la selección de variables para el ajuste estadístico y de la derivación de las implicaciones estadísticas de un diagrama causal. La principal ventaja de los diagramas causales es hacer explícitas las hipótesis adyacentes al modelo considerado, permitiendo que sus implicaciones puedan ser analizadas críticamente, facilitando, de esta forma, la identificación de posibles fuentes de sesgo e incertidumbre en los resultados de un estudio epidemiológico.

Los sesgos en investigación clínica / Bias in clinical research

Uno de los mayores dilemas en investigación es la ocurrencia de errores, los que pueden darse por efecto del azar o de forma sistemática. Es así como, se puede considerar que existe sesgo cuando en el curso de una investigación se comete un error de forma sistemática, es decir no aparece como un hecho aleatorio o por efecto del azar. Los sesgos pueden ocurrir por un sinnúmero de causales; pero en términos generales, se acepta que los más frecuentes y quizás los de mayor relevancia son aquellos debidos al observador, a lo que se observa y a aquello con lo que se observa. Dicho de otra forma, el que mide, lo que se mide y con que se mide. Otro considerando a tener en cuenta es que un sesgo puede ocurrir en cualquier etapa del curso de una investigación, desde la planificación a la presentación de resultados y la publicación ulterior de estos. Por todo ello, el objetivo de este artículo es describir los conceptos que permitan comprender la importancia de los sesgos, conocer los más frecuentes en investigación clínica, su asociación con los distintos tipos de diseños de investigación y las estrategias que permiten minimizarlos y controlarlos.

One of the biggest dilemmas in clinical research is the occurrence of errors, which can occur by chance or systematic practice. Thus, we can consider that there is bias when in the course of an investigation a systematical error occurs and it is not listed as a random occurrence or by chance. Biases can occur for different causes, but it is generally accepted that the most common and perhaps the most important are those due to the observer, what is observed, and that with which it is observed. In other words, who measured, what is measured, and the instrument that is being used to measure. Another consideration to keep in mind refers to the concept that bias can occur at any stage of the course of an investigation, from the initial planning through the analysis and the results presentation and it subsequent publication. Therefore, the purpose of this paper is to describe the concepts for understanding the importance of the biases, knowing the most common biases in clinical research and its association with different types of research designs as well as the strategies to prevent and control it.

Prevalência da dor lombar no Brasil: uma revisão sistemática / La prevalencia de dolor lumbar en Brasil: una revisión sistemática / Low back pain prevalence in Brazil: a systematic review

O artigo descreve a qualidade metodológica dos estudos publicados sobre prevalência de dor lombar realizados no Brasil. Dezoito estudos foram considerados elegíveis após pesquisas nas seguintes bases de dados: LILACS, PubMed, Embase, CINAHL, SPORTDiscus e SciELO. Alto risco de viés foi encontrado nos critérios de validade externa relacionados com a amostragem, e viés de não-resposta. Considerando os critérios de validade interna, a principal fonte de viés estava relacionada com a falta de uma definição de caso aceitável, bem como a utilização de instrumentos que não apresentavam construto de confiabilidade e a validade provados. Nenhum estudo representativo com valores de prevalência da dor lombar no Brasil foi encontrado. Os trabalhos publicados incluídos nesta revisão apresentaram um alto risco de viés que afetam os dados de prevalência. Futuros estudos com desenho metodológico adequado são necessários, a fim de apresentar o real impacto da dor lombar no Brasil e permitir comparações.

El artículo describe la calidad metodológica de los estudios publicados sobre la prevalencia de dolor lumbar realizados en Brasil. Dieciocho estudios se consideraron elegibles, después de búsquedas en las siguientes bases de datos electrónicas: LILACS, PubMed, Embase, CINAHL, SPORTDiscus y SciELO. Se encontró una alta fuente de sesgo en los criterios de validez externos, relacionados con la toma de muestras, y el sesgo de no respuesta. Teniendo en cuenta los criterios de validez interna, la principal fuente de sesgo se relaciona con la falta de una definición de caso aceptable, y el uso de instrumentos que no tenían la fiabilidad y validez de constructo. No se encontraron estudios representativos que ofrecieran una prevalencia generalizable de dolor lumbar en Brasil. Los estudios publicados, incluidos en esta revisión, tenían un alto riesgo de sesgo que afecta a los datos de prevalencia. Son necesarios futuros estudios con diseño metodológico apropiado, con el fin de presentar el impacto real del dolor lumbar en Brasil para permitir comparaciones.

The article describes the methodological quality of published studies on prevalence of low back pain in Brazil. Eighteen studies were considered eligible after searches in the following electronic databases: LILACS, PubMed, Embase, CINAHL, SPORTDiscus and SciELO. A high source of bias was observed in the criteria for external validity related to sampling, in addition to non-response bias. Considering the criteria for internal validity, the main sources of bias were the lack of an acceptable definition of low back pain and the use of instruments that lacked proven reliability and validity. No representative study was found that provides a generalizable prevalence of low back pain in Brazil. The published studies included in this review showed a high risk of bias that affects the prevalence data. Future studies with appropriate methodological design are necessary to verify the real impact of low back pain in Brazil and allow comparisons.

Quality control rules used in external quality assessment of quantitative assay in clinical laboratories / 中华检验医学杂志

External quality assessments play important roles in quality improvement in clinical laboratories, but most laboratories focused on the unsatisfied data only.With appropriate quality controls, laboratories can detect not only the error sourses of unsatisfied data but the potential error sourse of satisfied data as well.

Concordancia entre informacoes do SISPRENATAL e o recordatorio maternoem relacao à idade gestacional no momento do inicio do cuidado pre-natal / Agreement between SISPRENATAL and mother's recall for gestational age at prenatal care initiation

Comparou-se o início da atenção pré-natal durante o primeiro trimestre da gravidez (adequação do início do acompanhamento) a partir de entrevistas com as mulheres e a coleta de dados junto ao sistema de informações de saúde pré-natal (SISPRENATAL). Foram entrevistadas 238 mulheres que fizeram o pré-natal nas Unidades da Saúde da Família em Vespasiano, Minas Gerais. Informações sobre a idade gestacional e primeira visita pré natal foram coletadas. As entrevistas e a análise do SISPRENATAL indicaram que cerca de 30% das mulheres tiveram início de acompanhamento pré-natal inadequado. Entrevistas e os dados do SISPRENATAL tiveram um nível razoável de concordância pela análise de adequação da iniciação (Kappa=0,35; IC 95%: 0,22-0,48). A partir de modelos de regressão observou-se que a concordância foi mais provável quando as mulheres se recordavam dos procedimentos de acompanhamento ou quando não utilizaram o setor privado. O uso do setor privado (16,4%) foi associado a data mais tardia de inclusão da gestante no SISPRENATAL, quando comparado com as entrevistas. Em resumo, diferenças entre o recordatório materno e o SISPRENATAL foram associadas à não lembrança das informações por parte das mulheres entrevistadas e ao acompanhamento junto ao setor privado. Apesar dalimitação do viés de memória, o recordatório materno foi considerado mais fidedigno do que o SISPRENATAL na obtenção de dados sobre o início do acompanhamento da gestante na rede pública de saúde.

We compared the initiation of prenatal care during the first trimester of pregnancy (adequacy of initiation) between mother's recall and the prenatal health information system (SISPRENATAL). We asked 238 women that received prenatal care at Family Health Units in Vespasiano, Minas Gerais their gestational age at first prenatal visit. Both recall and SISPRENATAL indicated that 30% of women had inadequate initiation. There was fair agreement in the adequacy of initiation (Kappa=0.35, 95% CI: 0.22-0.48) between recall and SISPRENATAL. Through regression models, we found that agreement was more likely with mother's shorter recall period and non-use of the private sector. Use of the private sector (16.4%) was also correlated with a later date of initiation by SISPRENATAL than by mother's recall. In sum, differences in the adequacy of initiation between recall and SISPRENATAL were associated with longer recall periods and with use of the private sector. Despite the limitation of recall bias, mother's recall is preferable to SISPRENATAL for capturing the public use by the pregnant women.

Data analysis of 2013 national trueness verification project of HbA1c measurement / 中华检验医学杂志

Objective To assess system deviation of HbA1c measurement in clinical laboratories in China by the national trueness verification project.Methods Bias assessing research.Two lots samples of human whole blood pools with different HbA1c concentration levels were prepared and sent to laboratories by dry ice package.Laboratories were asked to measure these samples in 5 repeats per set in three consecutive Wednesday separately,results were reported through Web-based software.Meanwhile the IFCC reference measurement procedure was applied to assign HbA1c reference values for the two lots samples.The following information or data were analyzed:measurement systems,intra-lab CVs and inter-lab robust CVs of all laboratories,inter-lab robust CVs and bias based on peer groups,et.al.The criterion of bias was set at ± 4.5％.Results 106 of 120 laboratories submitted results,including 88 using high performance liquid chromatography method,13 using immune turbidimetry method and 5 using enzymatic methods the intra-lab CVs of lot 201311 ranged from 0 to 4.6％,with median of 1.1％,while for lot 201312 the intra-lab precision ranged from CV0 to CV4.5％,with median of CV0.9％.The inter-lab robust CVs of 201311 and 201312 with single determinations were 5.6％ and 6.1％ and inter-lab robust CVs of 201311 and 201312 of each lab's average results were 5.9％ and 5.6％ respectively.The inter-lab CVs of group BIO-RAD,TOSOH,ARKRAY and PRIMUS at two level were less than 5％.For all laboratories,the percents of pass of 201311 and 201312 were 61/106(57.5％) and 56/106(52.8％) respectively.The pass ratio of each group on two lots were as follows:of group BIO-RAD were both 19/45 (42.2％),of group TOSOH were 85％ (17/20) and 75％ (15/20),of group ARKRAY were 71.4％ (10/14) and 50％ (7/14),of group PRIMUS were 6/8,5/8; of group immune turbidimetric method were both 46.2％ (6/13) and of group enzymatic were both 3/5.Conclusions There were improvement for the performance of trueness of HbA1c measurement in domestic laboratories,while some of them should be addressed.Academic,research institutions,EQA organizer,manufacturers and clinical laboratories should work together to achieve the standardization of HbA1c measurement.

Inquerito por telefone: pesos de pos-estratificacao para corrigir vicios de baixa cobertura em Rio Branco, AC / Encuesta por telefono: pesos de post-estratificacion para corregir vicios de baja cobertura en Rio Branco, AC, Brasil / Telephone survey: post-stratification adjustments to compensate non-coverage bias in city of Rio Branco, Northern Brazil

OBJETIVO: Analisar efeitos do uso de pesos de pós-estratificação para corrigir vícios decorrentes da baixa cobertura de domicílios com telefone. MÉTODOS: Comparação dos resultados levantados pelo Inquérito Domiciliar com o Sistema de Vigilância de Fatores de Risco e Proteção para Doenças Crônicas por Inquérito Telefônico (Vigitel), em Rio Branco, AC, 2007, cuja cobertura era de 40% de telefonia fixa. O vício potencial do Vigitel foi expresso pela diferença entre as prevalências do Vigitel e do Inquérito Domiciliar, calculada a raiz quadrática do erro quadrático médio como medida de acurácia da estimativa. RESULTADOS: O procedimento de ponderação do Vigitel corrigiu o vício potencial nas prevalências de consumo de frutas, legumes e verduras, de carnes com gordura visível, o ser fumante, a autoavaliação do estado de saúde ruim e da morbidade referida de colesterol ou triglicéride. O procedimento adotado pelo Vigitel não reduziu o vício nas prevalências da prática de atividade física no tempo livre e de morbidade referida de asma, bronquite asmática, bronquite crônica ou enfisema. CONCLUSÕES: É necessário o uso de métodos alternativos de ponderação e a estratégia de seleção de variáveis externas para construção de pesos de pós-estratificação que minimizem o vício potencial das estimativas das variáveis decorrentes da baixa cobertura de domicílios com telefone fixo. .

OBJETIVO: Analizar efectos del uso de pesos de post-estratificación para corregir vicios consecuentes de la baja cobertura de domicilios con teléfono. MÉTODOS: Comparación de los resultados encontrados en la Encuesta Domiciliar con el Sistema de Vigilancia de Factores de Riesgo y Protección para Enfermedades Crónicas por Pesquisa Telefónica (Vigitel), en Rio Branco, AC, Brasil, 2007, cuya cobertura era de 40% de telefonía fija. El vicio potencial de Vigitel fue expresado por la diferencia entre las prevalencias de Vigitel y de la Encuesta Domiciliar, calculando la raíz cuadrada del error cuadrado promedio como medida de la precisión de la estimación. RESULTADOS: El procedimiento de ponderación de Vigitel corrigió el vicio potencial en las prevalencias de consumo de frutas, legumbres y verduras, de carnes con grasas visibles, el ser fumador, la autoevaluación del estado del mal estado de salud y de la morbilidad referida por el colesterol o triglicéridos. El procedimiento adoptado por Vigitel no redujo el vicio en las prevalencias de la práctica de actividad física en el tiempo libre y de morbilidad referida por el asma, bronquitis asmática, bronquitis crónica o enfisema. CONCLUSIONES: Es necesario el uso de métodos alternativos de ponderación y la estrategia de selección de variables externas para construcción de pesos de post-estratificación que minimicen el vicio potencial de las estimaciones de las variables consecuentes de la baja cobertura de domicilios con teléfono fijo. .

OBJECTIVE To evaluate the effects of using post-stratification weight to correct the bias due to low coverage of households with telephones. METHODS A Comparison was made of results collected by the Household Survey with those of the VIGITEL (Telephone Survey to Monitor Risk and Protective Factors for Chronic Diseases) in Rio Branco, Northern Brazil, in 2007 whose coverage was 40% of landline phones. The potential bias in the VIGITEL survey was expressed by the difference between the rates of prevalence of the VIGITEL and Household Survey, calculated as the square root mean square error (MSE) as a measure of the accuracy of the estimate. RESULTS The weighting procedure of VIGITEL corrected potential bias in the prevalence of consumption of fruit and vegetables, meat with visible fat, smoking, bad self-assessment of health status and morbidity of cholesterol or triglycerides. In the prevalence of physical activity in leisure time and morbidity of asthma, bronchial asthma, chronic bronchitis or emphysema, the procedure adopted by VIGITEL did not reduce the potential bias. CONCLUSIONS in order to construct post-stratification weights which minimize the potential bias in estimates of the variables due to low coverage of households with landlines, it becomes necessary to use alternative methods of weighting and strategies of selecting external variables. .

Concordância entre informações do Cartão da Gestante e da memória materna sobre assistência pré-natal / Agreement between information from the Pregnant Card and the mother's memory of antenatal care

Este estudo seccional objetivou verificar a concordância entre as informações prestadas por puérperas e as registradas nos cartões das gestantes sobre assistência pré-natal no Sistema Único de Saúde da Região Metropolitana da Grande Vitória, Espírito Santo, Brasil. Considerou-se uma população de estudo de 1.035 puérperas, entrevistadas em oito maternidades, onde os cartões foram copiados. A representatividade da amostra foi garantida pela estratificação segundo a proporção de nascidos vivos. Informações foram coletadas, processadas e submetidas aos testes de kappa e McNemar. Os níveis de concordância sobre assistência pré-natal foram predominantemente ruins (kappa < 0,20). Puérperas tendem a superestimar a quantidade de consultas pré-natais (McNemar = 51,73; valor de p = 0,001), afirmar doenças gestacionais, como diabetes, anemia, hipertensão e infecções urinárias, relatar a execução de exames laboratoriais e clínicos. Os resultados sugerem uma reflexão sobre dados utilizados para o planejamento de políticas em saúde pública materno-infantil, visto que há variação conforme a fonte de informação.

This cross-sectional study aimed to verify agreement between information given by mothers after delivery and data recorded on Pregnant Cards about antenatal care under the Brazilian Unified National Health System in the Metropolitan Region of Vitória, Espírito Santo State, Brazil. The study considered a population of 1,035 postpartum mothers interviewed in eight hospitals, where the cards were copied. The representativeness of the sample was guaranteedby stratification according to the proportion of births. Kappa and McNemar tests were carried out with the collected and processed information. Agreement levels regarding antenatal care were predominantly poor (kappa < 0.20). Mothers tend to: overestimate the number of antenatal visits (McNemar = 51.73; p-value = 0.001); affirm diseases during pregnancy, such as diabetes, anemia, hypertension and urinary infections; report the performance of laboratory tests; report the carrying out of clinical examinations. Results suggest the need to reflect on the type of data used for planning and implementing maternal and child public health polices, since data varies depending on the information source.

Peso e altura autorreferidos para determinação do estado nutricional de adultos e idosos: validade e implicações em análises de dados / Self-reported weight and height for determining nutritional status of adults and elderly: validity and implications for data analysis

Analisou-se a validade do peso e altura autorreferidos para determinação do estado nutricional, e as implicações do seu uso em análises de associação com desfechos em saúde. Baseando-se em um estudo transversal de base populacional realizado em Pelotas, Rio Grande do Sul, Brasil, em 2007 (n = 2.986), sorteou-se uma subamostra de 276 indivíduos com idade > 20 anos. Em média, o peso autorreferido foi similar ao medido; a altura medida foi superestimada nos homens (1,4cm) e nas mulheres (2,5cm); o índice de massa corporal (IMC) real foi subestimado em quase 1kg/m². Mesmo com diferenças médias pequenas, a variabilidade dos dados foi grande. Sexo, idade e escolaridade influenciaram nos resultados. O uso de medidas autorreferidas gerou subestimativas de sobrepeso e obesidade, assim como erros imprevisíveis em análises de associação com desfechos em saúde (subestimativa, superestimativa e inversão nas medidas reais de efeito). Equações de correção reduziram a média das diferenças com os valores medidos, mas não reduziram a variabilidade das diferenças e nem solucionaram erros de classificação ou vieses nas associações.

This study evaluated the validity of self-reported weight and height for determining nutritional status and the implications of their use for analyzing associations with health outcomes. A population-based cross-sectional study in Pelotas, Rio Grande do Sul State, Brazil, in 2007 (n = 2,986) drew a sub-sample of 276 individuals aged > 20 years. Mean self-reported weight was similar to measured weight; height was overestimated in men (1.4cm) and women (2.5cm); real body mass index (BMI) was underestimated by about 1kg/m². Even with small mean differences, data variability was great. The results were influenced by gender, age, and schooling. The use of self-reported measures underestimated prevalence of overweight and obesity, and unpredictable errors were found in the analysis of association with health outcomes (underestimation, overestimation, and reversal of real effect measures). Correction equations reduced the mean differences but did not resolve variability of the differences, classification errors, or biases in the associations.

Trueness verification and traceability assessment of results from a routine chemistry system for measurement of urea and creatinine in serum / 中华检验医学杂志

Objective To verify the trueness and assess the traceability of results from a routine chemistry system procedure for measurement of urea and ereatinine in serun.Methods Series of fresh frozen patieot sera,whose values of urea or creatinine were assigned by isotope dilution gas chromatography mass spectrometry (ID-GC/MS) or isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS),were chosen to be analyzed by a routine chemistry system.The measurement results of urea and creatinine by the routine chemistry system were used for linear regression analysis against the assigned values bv the ID-MS method to calculate the percentage deviation and assess the expected bias.Results For urea and creatinine,the linear regression equations between the routine chemistry system and ID-MS methods were Y =0.9890X + 0.0192 (R2 =0.9990) and Y =0.9815X-6.4794 (R2 =0.9989),and the average percentage bias were-0.41％ (P ＞0.05) and-4.20％ (P ＜ 0.05),respectively.The expected percentage bias at three medical decision levels were-0.46％,-0.83％ and-0.96％ for urea and -15.90％,-5.87％ and-2.95％ for creatinine.Conclusions The results of urea analyzed by the routine chemistry system were consistent with the ID-MS method,which suggested that the results of the routine system procedure could be traced to ID-GC/MS method.For creatinine,the bias between the results of routine procedures and the assigned values met the minimum acceptance criteria' derived from biologic deviations,which would be better if its specificity improved.

Accuracy investigation of commonly used creatinine assay systems / 中华检验医学杂志

Objective To evaluate the accuracy of Cr measurement value from commonly used homogenous detection systems,to investigate the variation among different systems and the corresponding bias of eGFR.Methods According to the CLSI EP14-A2 protocol,commutability of LN24 was validated among 10 enzymatic assays and 1 picrate assay.LN24 included 6 vials of solution with Cr values assigned by IDMS at NIST,and concentrations of Cr for each vial were 68.1,126.9,185.7,244.5,303.2 and 361.9μmol/L LN24 was used to evaluate the accuracy of the included systems and the variation among them,and the assigned values were taken as the target values.eGFR were calculated by MDRD equation using IDMStraced picrate Cr and CKD-EPI equation using enzymatic Cr.Results Commutability was exist among the 11 systems for LN24 detection.Four systems showed bias ＜ 4.4 μmol/L at each level of LN24,two system showed bias ＞4.4 μmol/L at each level of LN24,one system showed a fixed negative bias( -4.2 ±0.7)μ mol/L,the other 4 systems showed diverse bias at different levels.Cr-bias-caused eGFR bias could reach 14.9 ml · min-1 · (1.73 m2) -1 at Cr level of 68.1 μmol/L SD among systems ascended with Cr level (2.6 -6.1 μmol/L) ;CV among systems descended with Cr level(4.0％ - 1.7％ ) ;After the 2 systems with obvious negative bias were removed,SD,CV among systems and eGFR bias decreased obviously.By measuring fresh serum,it was found that Cr bias among enzymatic systems was mostly ＜ 10 μmol/L;that between enzymatic assays and picrate assay was much diffused(from - 15 to 20 μmol/L).When Cr ＜ 100μmol/L,the eGFR difference between result of MDRD equation and that of CKD-EPI equation ranged from - 18 to 40 ml · min-1 (1.73 m2) -1.Conclusions Some enzymatic systems show good accuracy.Difference of Cr value is relatively fixed among enzymatic systems,and comparability can be reached through mathematic way.Un-acceptable difference between picrate assay and enzymatic assays still exists,thus comparability cannot be reached through mathematic way.At low Cr level,bias of Cr and using different equations may lead to significant bias of eGFR.We recommend that clinical laboratory should pay much attention to the accuracy and comparability at low level of Cr,and use uniform equation to calculate eGFR.

Catálogo de sesgos o errores en cuestionarios sobre salud / Catalog of bias in health questionnaires

El cuestionario es ampliamente utilizado en el sector salud para recolectar información y se ha habido alguna discusión sobre la extensión y las fuentes de sesgos u errores que afectan la validez de la información obtenida, pero no hay una clara conciencia de la magnitud ni de la diversidad de los mismos. Se presentan y discuten los más resaltantes errores o sesgos en cuestionarios en el sector salud, basándonos en el trabajo previo de Choi y Pak. Objetivo: Este artículo intenta contribuirá a llevar al tapete de discusión el tema de los mecanismos y la dinámica de potenciales sesgos en cuestionarios del sector salud. Método: se realizó revisión de la literatura y se identificaron ejemplos extraídos de cuestionarios utilizados en diferentes proyectos, disponibles en forma impresa o en portales de internet de acceso público. Resultados: Se identificaron 48 tipos diferentes de sesgo, se discute cada uno y se presentan formas de minimizarlos o evitarlos. Presenta una tabla resumen que se podría usar como tabla de cotejo, útil para prevenir y minimizar los potenciales sesgos. Discusión: el cuestionario es una herramienta común en diversas actividades del sector salud, no obstante se imparte poca capacitación formal sobre su uso en la mayoría de las especialidades del sector. Este artículo permite reducir la posibilidad de errores o sesgos que pueden invalidar la información, al presentar las posibilidades de error de una forma útil y accesible al usuario no experto en la materia

Food insecurity measurement and indicators / Indicadores e medidas de insegurança alimentar

The United Nations define food security as "People having at all times, physical, social and economic access to sufficient, safe and nutritious food which meets their dietary needs and food preferences for an active and healthy life." There are five methods that are commonly applied in national surveys that can be used to assess food insecurity. Of these, four are indirect or derivative measures of food insecurity (United Nations Food and Agriculture Organization method, household expenditure surveys, dietary intake assessment and anthropometry). The only method that represents a fundamental or direct measure of food insecurity is the one based on experience-based food insecurity scales. All the methods complement each other and the method of choice depends on the question being answered and the economic and logistical resources available to collect valid data. All the methods have serious measurement error issues that can be reduced by fully understanding the principles underlying them and the use of highly trained and standardized research field workers. As shown in Brazil, the use of experience-based food insecurity measurement scales for mapping, targeting, and understanding the determinants and consequences of food insecurity is very promising. Thus, we recommend the Latin American and Caribbean Region to work towards the adoption of a single regional module that can be adapted to the local contexts based on qualitative cognitive research followed by quantitative confirmation of the scale's psychometric properties. The Brazilian experience-based food insecurity measurement project is likely to provide useful insights to other countries in the region.

As Nações Unidas definem Segurança Alimentar como a situação em que "as pessoas têm a todo tempo, acesso físico, social e econômico a alimentação segura, nutritiva e que atende suas necessidades dietéticas, com alimentos de sua preferência para uma vida ativa e saudável". Existem cinco métodos comumente utilizados em inquéritos nacionais para avaliação de insegurança alimentar. Desses, quatro são indiretos, ou medidas derivadas de insegurança alimentar (método da Organização das Nações Unidas para Agricultura e Alimentação, pesquisas de despesas familiares, avaliação de consumo e antropometria). O único método para medida direta ou fundamental de insegurança alimentar é representado por uma escala fundamentada na experiência de insegurança alimentar. Todos os métodos complementam-se mutuamente, o de escolha dependerá das perguntas a serem respondidas e dos recursos econômicos e logísticos disponíveis para coletar informações válidas. Todos os métodos possuem problemas sérios de erros de medida, que poderão ser reduzidos pelo conhecimento dos princípios nos quais estão baseados, além do envolvimento de pesquisadores de campo bem capacitados e padronizados. É promissor, como foi mostrado no Brasil, o uso de escala de medida baseada na experiência de insegurança alimentar, para mapear, identificar populações vulneráveis, compreender seus determinantes e conseqüências. Por essas razões, se recomendam, para a América Latina e o Caribe, trabalhos visando à adoção de instrumento regional único, adaptado aos contextos locais, a partir de investigações cognitivas qualitativas, seguidas de pesquisas de confirmação quantitativas das propriedades psicométricas das escalas. A experiência brasileira do projeto de medida de insegurança alimentar, provavelmente, oferecerá subsídios idéias úteis para outros países da região.

Metodología y lectura crítica de estudios Factores de confusión / Medical Studies` Methodology and Critical Reading. Factors leading to Confusion

Objetivo: describir la definición de los factores de confusión, dar algunos ejemplos y herramientas para su determinación y sugerir estrategias para reducir la confusión dentro del diseño de estudios. Metodología: se hace una descripción corta de las expresiones confusión y factores de confusión, y se describen algunos ejemplos. Se explican algunos métodos para su consideración dentro de la realización de diferentes estudios y las formas de mejorar su diseño. Conclusión: la confusión debe ser evaluada para describir la verdadera relación entre las variables.

Objective: To describe the definition of confounding factors, give some examples and tools for their determination, and to suggest strategies to reduce confusion in study designs. Methods: The terms confusion and confounding factors are briefly explained and some examples are given. Some of the methods used to assess them in the course of different studies and the ways to improve the design of these studies are also addressed. Conclusion: Confusion should be evaluated in order to describe the true relationship between variables.

Evaluation of cystatin C with two kinds of detection systems / 中华检验医学杂志

Objective To evaluate the performance of Cys C results among two detection system.Methods The particle-enhanced immunonephrometic assay was used in Dade Behring BNII. Immunoturbic assay was used in Hitachi 7170 to evaluate the JING' YUAN reagents.We compared the precison,linearity,interference,correlation,and calibrators agreement with Dade Behring BNII.Results The total CV of the samples that contain 0.6-5.0 mg/L was less than 10%.The Dade Behring and JING'YUAN method showed good linearity.Haemoglobin(10 g/L),Bilirubin(300 mg/L), Vitamin C(5 g/L)in the tested sample had no significant interference in the assay(interference 0.05) between JING' YUAN and Dade Behring reagents.Values were slightly lower than that from the Dade Behring BNII method,the mean bias was-0.16.The bias range was 1.1%-23% between JING'YUAN and Dade Behring for one sample.Conclusions The precision,linearity and interference test were suitable for routine Cys C measurement on automated biochemistry analyzer,but results has bias.