Temporal Series Analysis of Population Cycle Threshold Counts as a Predictor of Surge in Cases and Hospitalizations during the SARS-CoV-2 Pandemic.

Tools to predict surges in cases and hospitalizations during the COVID-19 pandemic may help guide public health decisions. Low cycle threshold (CT) counts may indicate greater SARS-CoV-2 concentrations in the respiratory tract, and thereby may be used as a surrogate marker of enhanced viral transmission. Several population studies have found an association between the oscillations in the mean CT over time and the evolution of the pandemic. For the first time, we applied temporal series analysis (Granger-type causality) to validate the CT counts as an epidemiological marker of forthcoming pandemic waves using samples and analyzing cases and hospital admissions during the third pandemic wave (October 2020 to May 2021) in Madrid. A total of 22,906 SARS-CoV-2 RT-PCR-positive nasopharyngeal swabs were evaluated; the mean CT value was 27.4 (SD: 2.1) (22.2% below 20 cycles). During this period, 422,110 cases and 36,727 hospital admissions were also recorded. A temporal association was found between the CT counts and the cases of COVID-19 with a lag of 9-10 days (p ≤ 0.01) and hospital admissions by COVID-19 (p < 0.04) with a lag of 2-6 days. According to a validated method to prove associations between variables that change over time, the short-term evolution of average CT counts in the population may forecast the evolution of the COVID-19 pandemic.

Dynamics of Reverse Transcription-Polymerase Chain Reaction and Serologic Test Results in Children with SARS-CoV-2 Infection.

OBJECTIVES: To determine the time to reverse transcription-polymerase chain reaction (RT-PCR) negativity after the first positive RT-PCR test, factors associated with longer time to RT-PCR negativity, proportion of children seroconverting after proven severe acute respiratory syndrome coronavirus 2 infection, and factors associated with the lack of seroconversion. STUDY DESIGN: The Epidemiological Study of Coronavirus in Children of the Spanish Society of Pediatrics is a multicenter study conducted in Spanish children to assess the characteristics of coronavirus disease 2019. In a subset of patients, 3 serial RT-PCR tests on nasopharyngeal swab specimens were performed after the first RT-PCR test, and immunoglobulin G serology for severe acute respiratory syndrome coronavirus 2 antibodies was performed in the acute and follow-up (<14 and ≥14 days after diagnosis) phase. RESULTS: In total, 324 patients were included in the study. The median time to RT-PCR negativity was 17 days (IQR, 8-29 days), and 35% of patients remained positive more than 4 weeks after the first RT-PCR test. The probability of RT-PCR negativity did not differ across groups defined by sex, disease severity, immunosuppressive drugs, or clinical phenotype. Globally, 24% of children failed to seroconvert after infection. Seroconversion was associated with hospitalization, persistence of RT-PCR positivity, and days of fever. CONCLUSIONS: Time to RT-PCR negativity was long, regardless of the severity of symptoms or other patient features. This finding should be considered when interpreting RT-PCR results in a child with symptoms, especially those with mild symptoms. Seroprevalence and postimmunization studies should consider that 11 in 4 infected children fail to seroconvert.

Recomendaciones sobre el uso de pruebas antigénicas en el diagnóstico de la infección aguda por SARS-CoV-2 en la segunda onda pandémica: actitud en distintos contextos clínicos / Recommendations for use of antigenic tests in the diagnosis of acute SARS-CoV-2 infection in the second pandemic wave: attitude in different clinical settings

La alta transmisibilidad del SARS-CoV-2 antes y poco después de la aparición de los síntomas sugiere que sólo diagnosticar y aislar a pacientes sintomáticos puede no ser suficiente para interrumpir la propagación de la infección; por ello son también necesarias medidas de salud pública como el distanciamiento social. Adicionalmente será importante detectar a los nuevos infectados que permanecen asintomáticos, que pueden ascender al 50% o más de los casos. Las técnicas moleculares son el patrón de referencia para el diagnóstico de infección por SARS-CoV-2. Sin embargo, el uso masivo de estas técnicas ha generado algunos problemas. Por un lado, la escasez de los recursos (analizadores, fungibles y reactivos), y por otro el retraso en la notificación de resultados. Estos dos hechos se traducen en un retraso en la aplicación de las medidas de aislamiento entre casos y contactos, lo que favorece la expansión de la infección. Las pruebas de detección de antígenos son también métodos de diagnóstico directo, con la ventaja de obtener el resultado en pocos minutos y en el mismo lugar de atención. Además, la sencillez y el bajo coste de estas pruebas permiten repetirlas en días sucesivos en determinados contextos clínicos. La sensibilidad de las pruebas de antígenos es generalmente menor que la de las que detectan ácidos nucleicos, si bien su especificidad es comparable. Se ha comprobado que las pruebas antigénicas tienen más validez en los días alrededor del inicio de síntomas, cuando la carga viral en nasofaringe es mayor. Disponer de un análisis de detección viral rápido y en tiempo real como la prueba de antígenos se ha demostrado más útil para controlar la expansión de la infección que pruebas más sensibles, pero de mayor coste y tiempo de respuesta, como son las pruebas moleculares. Las principales instituciones sanitarias como la OMS, los CDC y el propio Ministerio de Sanidad del Gobierno de España plantean el uso de las pruebas antigénicas en una amplia variedad de estrategias para responder a la pandemia. El presente documento pretende servir de apoyo a los médicos implicados en la atención de pacientes con sospecha de infección por SC2, en el contexto de una incidencia creciente en España desde septiembre de 2020 que representa ya la segunda onda pandémica de COVID-19

The high transmissibility of SARS-CoV-2 before and shortly after the onset of symptoms suggests that only diagnosing and isolating symptomatic patients may not be sufficient to interrupt the spread of infection; therefore, public health measures such as personal distancing are also necessary. Additionally, it will be important to detect the newly infected individuals who remain asymptomatic, which may account for 50% or more of the cases. Molecular techniques are the "gold standard" for the diagnosis of SARS-CoV-2 infection. However, the massive use of these techniques has generated some problems. On the one hand, the scarcity of resources (analyzers, fungibles and reagents), and on the other the delay in the notification of results. These two facts translate into a lag in the application of isolation measures among cases and contacts, which favors the spread of the infection. Antigen detection tests are also direct diagnostic methods, with the advantage of obtaining the result in a few minutes and at the very "pointof-care". Furthermore, the simplicity and low cost of these tests allow them to be repeated on successive days in certain clinical settings. The sensitivity of antigen tests is generally lower than that of nucleic acid tests, although their specificity is comparable. Antigenic tests have been shown to be more valid in the days around the onset of symptoms, when the viral load in the nasopharynx is higher. Having a rapid and real-time viral detection assay such as the antigen test has been shown to be more useful to control the spread of the infection than more sensitive tests, but with greater cost and response time, such as in case of molecular tests. The main health institutions such as the WHO, the CDC and the Ministry of Health of the Government of Spain propose the use of antigenic tests in a wide variety of strategies to respond to the pandemic. This document aims to support physicians involved in the care of patients with suspected SC2 infection, in the context of a growing incidence in Spain since September 2020, which already represents the second pandemic wave of COVID-19

Secukinumab does not impair the immunogenic response to the influenza vaccine in patients.

Objective: To evaluate whether immunological response to influenza vaccination is impaired in patients who are receiving secukinumab. Patients and methods: Subjects suffering from psoriatic arthritis or ankylosing spondylitis who were receiving treatment with secukinumab and healthy volunteers were included.All participants received seasonal inactivated trivalent influenza vaccine recommended by the WHO in the 2017-2018 northern hemisphere influenza season, which contained an A/Michigan/45/2015 (H1N1)pdm09-like virus, an A/Hong Kong/4801/2014 (H3N2)-like virus and a B/Brisbane/60/2008-like virus.Haemagglutination inhibition was used to evaluate basal antibody (Ab) titres against the three influenza vaccine virus strains just before vaccination and at least 4 weeks after the vaccine administration. Response to vaccine was considered as >4-fold increases in Ab titre. Results: Thirty subjects, 17 patients and 13 healthy controls, with a follow-up duration of 33±8 days, were analysed. There were no demographic differences between groups. Patients and controls achieved a median of 4.6-fold and 4.0-fold increases, respectively, for anti H1N1 and almost 4.0 (3.7) for patients and 5.3 for controls for anti-B Ab. Both groups presented a poor response against H3N2, with <1.5-fold increase. Seroconversion rates were similar in both groups. Secukinumab did not influence the response to the influenza vaccine (relative risk: 1.09 (95% CI 0.58 to 2.07) for H1N1, RR: 1.53 (95% CI 0.15 to 15.0) for H3N2 and RR: 0.72 (95% CI 0.32 to 1.83) for B strain). Conclusion: In our study, secukinumab has no effect on the immunogenic response to the influenza vaccine.

Next generation sequencing for rapid diagnosis of a rare early onset spastic paraplegia: A novel pathological variant in FA2H gene / Secuenciación de nueva generación para el diagnóstico rápido de una paraparesia espástica rara de aparición infantil: nueva variante patológica en el gen FA2H

Introduction: Hereditary spastic paraplegia is a group of inherited neurological disorders with predominant manifestations of lower extremity weakness and severe spasticity. This is a genetically heterogeneous disorder very difficult to distinguish clinically with many genes described. Few patients with this condition have been previously reported. Patient and methods: We present a case of a 5 years old girl, born from consanguineous parents, with severe ataxia and progressive spasticity of low limbs. Due to the severity of the symptoms and the need for early diagnosis, next generation sequencing study of 37 genes implicated in spastic paraplegia was performed. Results: A novel pathological variant in FA2H gene was discovered. Father, mother and brother were heterozygous carriers. Conclusions: Spastic paraplegia due to mutations in FA2H is an under diagnosed condition, and it should always be considered in childhood onset of progressive pyramidal dysfunction. Next Generation Sequencing allows a simultaneous analysis of many genes, enables a fast diagnosis in complex disorders

Introducción: La paraparesia espástica es un grupo de enfermedades neurológicas hereditarias que cursan con debilidad de las extremidades inferiores y espasticidad severa. Es una enfermedad muy heterogénea, con muchos genes descritos y muy difícil de distinguir clínicamente. Hay pocos pacientes descritos con esta enfermedad. Pacientes y métodos: Se presenta un caso de una niña de 5 años, de padres consanguíneos, con una ataxia severa y espasticidad progresiva de los miembros inferiores. Dada la gravedad de la clínica y la necesidad de un diagnóstico temprano, se decide realizar un panel de secuenciación masiva de 37 genes implicados en paraparesia espástica. Resultados: Los resultados muestran una variante patológica no descrita previamente en el gen FA2H. El padre, la madre y el hermano resultan portadores heterocigotos. Conclusiones: La paraparesia espástica debida a mutaciones en el gen FA2H está infradiagnosticada y debería ser considerada siempre que aparezcan síntomas en la infancia de disfunción piramidal grave y progresiva. Los paneles de secuenciación masiva con el análisis simultáneo de varios genes están permitiendo un diagnóstico más rápido en enfermedades complejas

Category 1 external quality assessment program for serum creatinine.

BACKGROUND: The Commission of Analytical Quality and the Committee of External Quality Programs of Spanish Society of Laboratory Medicine (SEQC) in collaboration with the Dutch Foundation for the Quality organized the first national category 1 External Quality Assessment Programs (EQAP) pilot study. The aim is to evaluate the standardization of serum creatinine measurements in the Spanish laboratories through a category 1 external quality assurance program with commutable material and reference method assigned values. METHODS: A total of 87 Spanish laboratories were involved in this program in 2015. Each day a sample control was measured by duplicate during 6 consecutive days. Percentage deviations and coefficients of variation obtained were compared with quality specifications derived from biological variation. RESULTS: A total of 1044 creatinine results were obtained. Laboratories were coded in 11 different method-traceability combinations. Only enzymatic methods get all results within the acceptability limits. DISCUSSION: To participate in a category 1 EQAP is a valuable tool to assess the standardization degree in our country; a big effort should be made to promote laboratories to change their procedures and to use enzymatic creatinine methods, in order to achieve a satisfactory standardization degree for this important analyte.

Biologic Variation Approach to Daily Laboratory.

Biological variation gives valuable information about how the living organism regulates its constituents within and between subjects; this information on the behavior of body components allows us to derive consequences concerning reference populations and intervals. With a more pragmatic approach biological variation has three uses: setting the appropriate analytical performance specification for each analyte to limit the amount of error that laboratory could introduce in its measurements, to help distinguish health from disease, and to implement internal quality control with the automatic verification of results.

Laboratory parameters provided by Advia 2120 analyser identify structural haemoglobinopathy carriers and discriminate between Hb S trait and Hb C trait.

BACKGROUND: Haemoglobinopathies have spread owing to human migration, and the number of people needing diagnosis and management of these conditions is increasing. Clinicians need to accurately identify carriers and provide adequate genetic counselling in order to prevent the occurrence of homozygous or compound heterozygous offspring. OBJECTIVES: To identify red blood cell (RBC) laboratory parameters that discriminate between structural haemoglobinopathy carriers and healthy subjects, and to compare RBC laboratory indices between HbAS and HbAC individuals. METHODS: Samples of 500 variant Hb carriers (355 HbAS, 104 HbAC, 19 HbAD, 7 HbAE, 7 HbAO-Arab, 4 α-chain variants and 4 Hb Lepore) and 251 normal controls were run on an Advia 2120 analyser (Siemens). Classic haematological parameters and RBC populations were assessed in all subjects. A multivariable binary logistic regression model was created to predict the probability of a subject carrying any structural haemoglobinopathy. HbAS (n=355, 71%) and HbAC (n=104, 20.8%) subjects were compared. RESULTS: A clinical prediction rule was developed by assigning one point to each of the most efficient variables: mean corpuscular volume (MCV) <88.4 fL, RBC distribution width >13.4%, percentage of microcytic RBCs (%MICRO) >0.7% and the ratio of microcytic RBCs to hypochromic RBCs >0.8. A score of 0, 1, 2, 3 or 4, resulted in a probability of 9.6%, 36.3%, 66.7%, 85.2% or 98.3%, respectively. Among the most frequent variant Hb, HbAC subjects had lower values of parameters related to cell size (MCV, %MICRO) and higher values of parameters related to haemoglobin concentration (MCHC, %HYPER) than HbAS subjects. Coexistence of α-thalassaemia in both HbAS and HbAC individuals resulted in decreased Hb, MCV, MCH and MCHC. CONCLUSIONS: Structural haemoglobinopathy should be investigated in subjects belonging to ethnic groups with high prevalence of variant Hb and with a score of 3 or 4. Erythrocytes of HbAC subjects are smaller and denser than those of HbAS subjects.

Reticulocyte parameters of delta beta thalassaemia trait, beta thalassaemia trait and iron deficiency anaemia.

AIMS: To analyse the differences in reticulocyte indices between delta beta thalassaemia trait (δß-TT), beta thalassaemia trait (ß-TT) and iron deficiency anaemia (IDA), and to correlate those differences with the physiopathological features of these three types of microcytoses. METHODS: We performed a descriptive study of 428 samples (43 δß-TT, 179 ß-TT and 206 IDA) that were run on Advia 2120 analyser (Siemens). The following reticulocyte indices were assessed: absolute reticulocyte count (ARC), percentage of reticulocytes, mean corpuscular volume of reticulocytes (MCVr), haemoglobin content of reticulocytes (CHr), mean corpuscular haemoglobin concentration of reticulocytes, red blood cell distribution width of reticulocytes (RDWr), haemoglobin distribution width of reticulocytes (HDWr) and reticulocyte subpopulations based on their fluorescence according to mRNA (low (L-R), medium (M-R) and high (H-R)), MCV ratio and MCHC ratio. Correlation between fetal haemoglobin (HbF) and RDWr in patients with thalassaemia was evaluated. RESULTS: RDWr was significantly higher in δß-TT compared with ß-TT (15.03% vs 13.82%, p<0.001), and so were HDWr (3.65% vs 3.27%, p<0.001), CHr (23.68 vs 22.66 pg, p<0.001) and MCVr (88.3 vs 85.5 fL, p<0.001). A good correlation was observed between HbF and RDWr (r=0.551, p<0.001). IDA subjects have more immature reticulocytes, but less ARC than ß-TT, suggesting a certain degree of inefficient erythropoiesis in IDA in comparison with ß-TT. CONCLUSIONS: Previously described differences between δß-TT, ß-TT and IDA in the corpuscular indices of mature red blood cell can also be observed in reticulocytes. The degree of anisocytosis in reticulocytes from patients with thalassaemia is correlated with HbF.

The utility of multiparametric seven-color flow cytometry in the detection of double hit lymphoma in ascitic fluid samples.

Double-hit lymphoma (DHL) is a rare type of lymphoma with concurrent chromosomal translocations of C-MYC with BCL2 or BCL6, associated with unfavorable prognosis. We describe a case of DHL in a 79-year-old female patient previously diagnosed with diffuse large B-cell lymphoma (DLBCL) with an early relapse in the ascitic fluid. A seven-color multiparametric flow cytometry immunophenotyping study of the ascitic fluid was carried out, and revealed 99.78% of large in size and high cellular complexity B-cells positive for CD19, CD10 (64.27%), CD45 dim, CD22 dim, CD25 (60%), CD43 bright, CD38 bright, and IgM (18.53%); and negative for CD20, CD5, CD23, CD79b, CD103, CD200, CD11c, and FMC7, and 78.99% without light chain expression and 21% with Lambda chain restriction. Due to the expression of CD19 and CD10 with overexpression of BCL-2 protein and due to CD43 and CD38 positivity detected, those cells showed features between DLBCL and Burkitt lymphoma. Fluorescence in situ hybridization (FISH) confirmed both c-MYC/IGH and BCL2/IGH rearrangement. Our findings may help to identify cases requiring additional cytogenetic analysis. © 2015 International Clinical Cytometry Society.

Rationale for using data on biological variation.

The aims of this study are: 1) to use the data included in the biological variation (BV) database to address the usability of BV estimates; and 2) to use different examples from the authors' laboratories to illustrate the use and the usefulness of BV data in laboratory medicine. The BV database is an essential tool for laboratory management. Examples of application of data derived from BV are given in this paper, such as analytical performance specifications that have been included in various quality control software designed to optimize operative rules; also they have been incorporated as acceptability limits in external quality assurance reports. BV data from pathological status are of utmost interest for monitoring patients and differences between the intra-individual coefficients of variation (CVI) estimated from healthy and patients are shown. However, for a number of analytes there are limited data available and for many there are no data, consequently new studies should be encouraged at an international level. In addition, developing international criteria to evaluate publications dealing with the estimation of BV components would be of the utmost interest. We are ready and willing to collaborate with such worthy initiatives. The first EFLM strategic conference on analytical performance specifications is an excellent opportunity for debating these ideas.

Biological variation database: structure and criteria used for generation and update.

BACKGROUND: Numerical data on the components of biological variation (BV) have many uses in laboratory medicine, including in the setting of analytical quality specifications, generation of reference change values and assessment of the utility of conventional reference values. METHODS: Generation of a series of up-to-date comprehensive database of components of BV was initiated in 1997, integrating the more relevant information found in publications concerning BV. A scoring system was designed to evaluate the robustness of the data included. The database has been updated every 2 years, made available on the Internet and derived analytical quality specifications for imprecision, bias and total allowable error included in the tabulation of data. RESULTS AND CONCLUSIONS: Our aim here is to document, in detail, the methodology we used to evaluate the reliability of the included data compiled from the published literature. To date, our approach has not been explicitly documented, although the principles have been presented at many symposia, courses and conferences.

δß-Thalassemia trait: how can we discriminate it from ß-thalassemia trait and iron deficiency anemia?

OBJECTIVES: To analyze the differences not only in classic hematologic parameters but also in RBC subpopulations among δß-thalassemia trait (δß-TT), ß-thalassemia trait (ß-TT), and iron deficiency anemia (IDA) and to evaluate the role of fetal hemoglobin (HbF) in elevated RBC distribution width (RDW). METHODS: Samples from 553 patients with microcytosis (74 δß-TT, 272 ß-TT, and 207 IDA) were run on an Advia 2120i analyzer (Siemens Medical Solutions Diagnostics, Tarrytown, NY). Classic hematologic parameters and RBC subpopulations were assessed. The correlation between HbF and RDW in patients with thalassemia (both ß and δß) was evaluated. An independent sample t test was used to compare classic hematologic parameters and RBC subpopulations among ß-TT, IDA, and δß-TT and receiver operating characteristic curves performed in the significant comparisons. RESULTS: RDW was significantly higher in δß-TT compared with ß-TT (18.79% vs 16.04%, P < .001), as was mean corpuscular volume (66.39 vs 64.82 fL, P < .001), mean corpuscular hemoglobin (20.73 vs 20.04 pg, P < .001), and mean corpuscular hemoglobin concentration (31.16 vs 30.66 g/dL, P = .03). Pearson coefficient showed a good correlation between HbF and RDW. The values obtained for all the parameters were significantly different (P < .001) between patients with thalassemia (ß and δß) and IDA. CONCLUSIONS: RDW is the best parameter to discriminate δß-TT from ß-TT. The degree of anisocytosis in patients with ß-TT and δß-TT is strongly correlated with HbF.

Accelerated renal disease is associated with the development of metabolic syndrome in a glucolipotoxic mouse model.

Individuals with metabolic syndrome are at high risk of developing chronic kidney disease (CKD) through unclear pathogenic mechanisms. Obesity and diabetes are known to induce glucolipotoxic effects in metabolically relevant organs. However, the pathogenic role of glucolipotoxicity in the aetiology of diabetic nephropathy is debated. We generated a murine model, the POKO mouse, obtained by crossing the peroxisome proliferator-activated receptor gamma 2 (PPARγ2) knockout (KO) mouse into a genetically obese ob/ob background. We have previously shown that the POKO mice showed: hyperphagia, insulin resistance, hyperglycaemia and dyslipidaemia as early as 4 weeks of age, and developed a complete loss of normal ß-cell function by 16 weeks of age. Metabolic phenotyping of the POKO model has led to investigation of the structural and functional changes in the kidney and changes in blood pressure in these mice. Here we demonstrate that the POKO mouse is a model of renal disease that is accelerated by high levels of glucose and lipid accumulation. Similar to ob/ob mice, at 4 weeks of age these animals exhibited an increased urinary albumin:creatinine ratio and significantly increased blood pressure, but in contrast showed a significant increase in the renal hypertrophy index and an associated increase in p27(Kip1) expression compared with their obese littermates. Moreover, at 4 weeks of age POKO mice showed insulin resistance, an alteration of lipid metabolism and glomeruli damage associated with increased transforming growth factor beta (TGFß) and parathyroid hormone-related protein (PTHrP) expression. At this age, levels of proinflammatory molecules, such as monocyte chemoattractant protein-1 (MCP-1), and fibrotic factors were also increased at the glomerular level compared with levels in ob/ob mice. At 12 weeks of age, renal damage was fully established. These data suggest an accelerated lesion through glucolipotoxic effects in the renal pathogenesis in POKO mice.

miR-143, miR-222, and miR-452 are useful as tumor stratification and noninvasive diagnostic biomarkers for bladder cancer.

Altered microRNA (miRNA) expression may occur early in bladder cancer and may play a role in carcinogenesis and tumor behavior. We evaluated whether alterations in miRNA expression could improve disease stratification and outcome prognosis in bladder tumors and noninvasive diagnosis in urinary samples. miR-143, miR-222, and miR-452 expression levels were analyzed by quantitative RT-PCR (RT-qPCR) in paired urinary and matching tumors and in two independent prospective series of tumors and urinary specimens. Differential expression of miR-143, miR-222, and miR-452 in urine were verified by in situ hybridization in matching tumors. Tumor miRNA expression by RT-qPCR correlated with tumor grade, size, and presence of carcinoma in situ for miR-222, recurrence (miR-222 and miR-143), progression (miR-222 and miR-143), disease-specific survival (miR-222), and overall survival (miR-222). Protein expression patterns of potential miRNA targets, including vascular endothelial growth factor, BCL2, v-erb-b2 erythroblastic leukemia viral oncogene (ERBB) homolog 3, and ERBB4, were evaluated by IHC in tissue arrays containing tumors for which miRNAs were assessed by RT-qPCR. Target expression correlated with expression of their predicted regulatory miRNAs, recurrence (ERBB3), progression (ERBB4), disease-specific survival (ERBB3 and ERBB4), and overall survival (ERBB3 and ERBB4). Furthermore, RT-qPCR of miR-452 (area under the curve, 0.848) and miR-222 (area under the curve, 0.718) in urine provided high accuracies for bladder cancer diagnosis. Thus, bladder tumors were characterized by changes in miRNA expression that could aid in tumor stratification and clinical outcome prognosis, and miRNAs were detected in urinary specimens for noninvasive diagnosis.

Variación biológica. Revisión desde una perspectiva práctica / Biological variation. A review from a practical perspective

Los autores realizan una revisión exhaustiva sobre la variación biológica, con el objeto de resaltar su aplicación práctica en la rutina diaria del laboratorio clínico. Se describe brevemente el método de estimación de los componentes de la variación biológica y se detalla la base de datos actualizada bianualmente y disponible para los profesionales del sector. Se pormenoriza el uso práctico en el control interno del proceso analítico, en la evaluación de los datos del control interno y externo, así como en la detección de errores analíticos y extraanalíticos. Finalmente, se explica con claridad cómo notificar la posibilidad de un cambio significativo en el estado de salud del paciente en el informe analítico (AU)

This is an exhaustive review on biological variation, which aims to highlight its practical application in daily routine of clinical laboratories. The methodology to estimate the components of biological variation is summarised and a database, which is updated every two years and available to professionals of the area, is explained in detail. Daily application of data derived from biological variation in daily practice in internal and external quality control, as well as, in the detection of analytical and non-analytical errors is clearly explained. Last, but not least, examples are given on how to notify to clinicians on possible changes in patients health status (AU)

Aplicación del modelo Seis-Sigma en la mejora de la calidad analítica del laboratorio clínico / Application of the Six-Sigma model to improve analytical quality in the clinical laboratory

Introducción. El modelo Seis Sigma es una herramienta de gestión de la calidad que se basa en la medida de la variabilidad de un proceso, en términos de desviación típica o de fallos por millón. Implica haber definido previamente una especificación de la calidad para el proceso que se investiga. Material y método. Este trabajo estudia los datos obtenidos en los programas de garantía externa de la calidad de la Sociedad Española de Bioquímica Clínica y Patología Molecular (SEQC), con el propósito de deducir consecuencias prácticas que aseguren el diagnóstico y el seguimiento correctos del paciente, mediante el informe aportado por el laboratorio. Se incluyen magnitudes biológicas con especificaciones de la calidad definidas para situaciones clínicas concretas (colesterol, glucosa, glucohemoglobina y antígeno prostático específico total) y con valores de variación biológica bajos (ión sodio, albúmina), intermedios (colesterol, creatinina, glucosa) y altos (hierro, triglicéridos). El valor sigma se calcula mediante el cociente entre el límite de tolerancia establecido y la variabilidad del proceso. Resultados. Los valores sigma obtenidos son adecuados (>=3) si se toman especificaciones muy permisivas, mientras que no lo son cuando se desea cumplir la especificación derivada de la variación biológica. Ello indica que los instrumentos y métodos analíticos disponibles en nuestro mercado requieren un procedimiento de control de la calidad muy cuidadoso (procesamiento de varias muestras control, necesidad de realizar repeticiones, etc.). Conclusiones. En ningún caso se debe confundir el objetivo de alcanzar la calidad necesaria para el adecuado uso clínico del informe analítico con el de conseguir un laboratorio industrialmente productivo; ambos forman parte del concepto de calidad total(AU)

Introduction. The Six Sigma model is a management tool based on measuring process variability, in terms of standard deviation or defects per million. It involves defining the specifications of the quality desired for the process investigated. Material and method. This work uses data obtained by the laboratories participating in the external surveys organized by the Spanish Society of Clinical Biochemistry and Molecular Pathology (SEQC), with the aim of promoting practical recommendations for assuring satisfactory patient diagnosis or monitoring through the laboratory report. The analytes included have quality specifications defined for specific clinical situations (cholesterol, glucose, HbA1C, total PSA) and have narrow (albumin, sodium), medium (cholesterol, creatinine, glucose) and wide (iron, triglyceride) biological variations. Results from control materials with the relevant concentrations to make clinical decisions have been used in this study. Sigma matrix is calculated from the ratio between quality specification and process coefficient of variation. Results. Results obtained show that sigma values are good (>=3) when using permissive quality specifications, whereas they are poor if quality specifications are derived from biological variation. This finding indicates that instruments and methods available in our field require a strict quality control procedure (several control samples per run, repeated tests, etc.). Conclusions. The objective of obtaining the quality required for adequate clinical use, must not be confused with that of achieving an economically productive laboratory; both are part of the concept of total quality management(AU)

Variación biológica en patologías: revisión de datos y consecuencias clínicas / Biological variation in disease: data review and clinical consequences

Introducción. La variación biológica (VB) es la fluctuación fisiológica de los constituyentes de los fluidos humanos alrededor del punto homeostático, considerada de forma individual (CVI) o entre diferentes individuos. Los datos derivados de su estudio se usan como propuesta del valor de referencia de un cambio (VRC) entre resultados seriados de un mismo individuo. El VRC estimado a partir de individuos sanos se ha utilizado en el control de la evolución clínica de los pacientes con el fin de discriminar si se produce un cambio significativo en una serie de resultados analíticos. Objetivo. El objetivo del presente trabajo es revisar los datos de VB en situaciones patológicas para aplicarla al uso de la práctica clínica, especialmente en el seguimiento de pacientes. Material y método. El material usado en este estudio se recogió a partir de artículos referenciados en los buscadores electrónicos, libros y tesis doctorales. Se ha recopilado y ordenado alfabéticamente un total de 66 magnitudes biológicas en 34 situaciones patológicas. Resultados y conclusiones. Para la mayoría de las magnitudes estudiadas, los valores de CVI en estados patológicos son similares a los encontrados en individuos sanos. Sin embargo, para las magnitudes consideradas como marcadores específicos de órgano, los valores de CVI son muy diferentes (superiores o inferiores) a los obtenidos en personas sanas. Esto implica que los valores VRC procedentes de personas sanas pueden no ser adecuados para el seguimiento de los pacientes. Hay un riesgo de que se produzcan falsos positivos (o negativos) sobre cambios del estado de salud, con sus correspondientes implicaciones clínicas(AU)

Introduction. Biological variation (BV) refers to the natural fluctuation of a physiological constituent around the homeostatic set point within a person (CVI), as well as the natural variation between persons. The data derived from the components of BV are used to propose the reference change value (RCV) for monitoring patients. Objective. The aim of this review is to show the state of the art for biological variation data in non-healthy situations in order to have an indication of whether the data derived in specific pathological situations might be useful for clinical applications. Material and method. The information used in this study was retrieved from published articles referenced in electronic search systems, books and a doctoral thesis. The analytes studied were listed in alphabetical order. Results and conclusions. For the majority of quantities studied, CVI values are of the same order in disease and health: thus the use of RCV derived from healthy subjects for monitoring patients would be reasonable. However, for a small number of quantities considered to be disease specific markers, the CVI differed from those in health. This could mean that RCV derived from healthy CVI may not be appropriate for monitoring patients in certain diseases. Hence, disease specific RCV may be clinically useful(AU)

Within-subject biological variation in disease: collated data and clinical consequences.

Quantitative data on the components of biological variation (BV) are used for several purposes, including calculating the reference change value (RCV) required for the assessment of the significance of changes in serial results in an individual. Pathology may modify the set point in diseased patients and, more importantly, the variation around that set-point. Our aim was to collate all published BV data in situations other than health. We report the within-subject coefficient of variation (CV(I)) for 66 quantities in 34 disease states. We compared the results with the CV(I) determined in healthy individuals and examined whether the data derived in specific diseases could be useful for clinical applications. For the majority of quantities studied, CV(I) values are of the same order in disease and health: thus the use of RCV derived from healthy subjects for monitoring patients would be reasonable. However, for a small number of quantities considered to be disease specific markers, the CV(I) differed from those in health. This could mean that RCV derived from healthy CV(I) may be inappropriate for monitoring patients in certain diseases. Hence, disease-specific RCVs may be clinically useful.

Integration of data derived from biological variation into the quality management system.

BACKGROUND: [corrected] Data on within- and between-subject biological variation are available for around 250 analytes commonly used in medical laboratories. METHODS: Integration of this data into the quality system occurs at all three levels of laboratory activity: (a) Preanalytic process: biological variation provides the basis for selecting the most appropriate specimen for analysis, for defining sample stability and for deciding suitable timing between samplings; (b) analytic process: biological variation-derived goals are fundamental for designing internal quality control procedures, and for evaluating laboratory performance; and (c) postanalytic process: delta checks based on within-subject biological variation values are used for validating results and for interpreting serial results from a patient. CONCLUSION: The biological variation is a pillar for managing quality in laboratory medicine.