Impact of rt-pcr test false-negative results for SARS-CoV-2 surveillance in Mexico

ABSTRACT Background: Underestimation of the number of cases during the coronavirus disease 2019 (COVID-19) pandemic has been a constant concern worldwide. Detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA using real-time reverse-transcription polymerase chain reaction (RT-PCR) is the most common method to confirm a case. However, these tests have suboptimal sensitivity. Objective: The objective of the study was to estimate the number of COVID-19 confirmed cases, intensive care unit (ICU) admissions and deaths in Mexico, accounting for the probabilities of false-negative tests. Methods: We used publicly available, national databases of all SARS-CoV-2 tests performed at public laboratories in Mexico between February 27 and October 31, 2020. We used the estimated probabilities of false-negative tests based on the day of clinical sample collection after symptom initiation calculated previously. With the resulting model, we estimated the corrected daily number of cases, ICU admissions, and deaths. Results: Among 2,024,822 people tested in Mexico between February 27 and October 31 with an available result, we estimated 1,248,583 (95% confidence interval 1,094,850-1,572,818) cases, compared to 902,343 cases reported with positive tests. ICU admissions and deaths were 15% and 8% higher than reported, respectively. Conclusion: Accounting for SARS-CoV-2 RT-PCR-based diagnostic testsҠprecision is a simple way to improve estimations for the true number of COVID-19 cases among tested persons.

Factores psicosociales asociados con el inicio tardío de tratamiento antirretroviral en pacientes mexicanos con VIH / Psychosocial factors associated with late HAART initiation in Mexican patients with HIV

Objetivo. Explorar la asociación entre variables psicosociales y el inicio tardío de tratamiento antirretroviral en una muestra de pacientes mexicanos con diagnóstico de VIH. Material y métodos. Estudio transversal en la clínica de VIH del Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, donde se aplicaron cuestionarios estructurados a 150 pacientes que iniciaron terapia antirretroviral altamente activa (TARAA) entre enero de 2010 y agosto de 2011. Se consideró inicio tardío (IT) de TARAA cuando los pacientes iniciaron el tratamiento con CD4 <200 células/mm³. Resultados. Mediante el análisis multivariado, se encontró que el principal factor psicosocial asociado con IT fue la percepción de autoestigma relacionada con el VIH/sida. Además, la realización de la prueba del VIH se asoció con la indicación médica y no con la iniciativa del paciente; a su vez, tener uno o más contactos médicos previos se relacionó con un mayor riesgo de presentar IT. Conclusiones. Los resultados sugieren la necesidad de intervenciones psicosociales dirigidas a disminuir la autoimagen negativa y actitudes y comportamientos estigmatizantes en grupos de riesgo.

Objective. To explore the association between psychosocial factors and late highly active antiretroviral therapy (HAART) initiation in a sample of Mexican patients with HIV. Materials and methods. We conducted a cross-sectional study at the HIV Clinic of the Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (INCMNSZ), and applied structured questionnaires to 150 patients who initiated HAART between January 2010 and August 2011. Late HAART initiation (LHI) was considered when patients started HAART with CD4 counts of <200+ cells/mm³. Results. By multivariate analysis, the strongest psychosocial risk factor for LHI observed was self-stigma towards HIV/AIDS. In addition, being tested by medical prescription, not by own initiative, as well as having one or more previous medical contacts, were associated with greater risk for LH. Conclusions. Our findings suggest the need to develop psychosocial interventions to decrease negative self-image and stigmatizing attitudes and behaviors in risk groups for HIV in Mexico.

Socioeconomic status and misperception of body mass index among Mexican adults / Nivel socioeconómico y percepción del índice de masa corporal en adultos en México

Objective. To estimate the association between perceived body mass index (BMI) and socioeconomic variables in adults in Mexico. Materials and methods. We studied 32052 adults from the Mexican National Health and Nutrition Survey of 2006. We estimated BMI misperception by comparing the respondent's weight perception (as categories of BMI) with the corresponding category according to measured weight and height. Misperception was defined as respondent's perception of a BMI category different from their actual category. Socioeconomic status was assessed using household assets. Logistic and multinomial regression models by gender and BMI category were estimated. Results. Adult women and men highly underestimate their BMI category. We found that the probability of a correct classification was lower than the probability of getting a correct result by chance alone. Better educated and more affluent individuals are more likely to have a correct perception of their weight status, particularly among overweight adults. Conclusions. Given that a correct perception of weight has been associated with an increased search of weight control and that our results show that the studied population underestimated their BMI, interventions providing definitions and consequences of overweight and obesity and encouraging the population to monitor their weight could be beneficial.

Objetivo. Estimar la asociación entre la percepción del índice de masa corporal (IMC) y las variables socioeconómicas en adultos de México. Material y métodos. Se estudiaron 32052 adultos que participaron en la Encuesta Nacional de Salud y Nutrición 2006. Se estimó la percepción incorrecta del IMC clasificando la percepción del entrevistado sobre su peso en categorías de IMC y comparándola con la que le correspondía de acuerdo con la medición real de su peso y estatura. El nivel socioeconómico se evaluó mediante los activos en los hogares. Se estimaron modelos de regresión logística y multinomial por género y categoría de IMC. Resultados. Las mujeres y hombres adultos subestiman su categoría de IMC. La probabilidad de tener una percepción correcta es menor que la probabilidad de obtener un resultado correcto sólo por azar. Los individuos con mayor nivel de escolaridad y socioeconómico tienen mayor probabilidad de percibir correctamente su IMC, particularmente en personas con sobrepeso. Conclusiones. Dado que una correcta percepción del peso se ha asociado con mayor búsqueda de su control y que nuestros resultados muestran que la población estudiada subestima su IMC, las intervenciones que provean información sobre definiciones y consecuencias del sobrepeso y la obesidad y que promuevan el monitoreo del peso corporal pueden ser benéficas.

High prevalence of late diagnosis of HIV in Mexico during the HAART era

OBJECTIVE: To evaluate the prevalence of late HIV diagnosis (CD4<200 cell/mm³) in an HIV clinic in Mexico City between 2001-2008, to assess changes in this prevalence across the study period, and to determine the risk factors associated to late testing (LT). MATERIALS AND METHODS: Cross-sectional analysis including all patients recently diagnosed as HIV. We estimated the proportion of LT patients and compared demographic characteristics between those and all other. We determine the risk factors associated to LT using logistic regression methods. RESULTS: Sixty one percent of LT patients present when are diagnosed for the first time. The prevalence did not decrease between 2001 and 2008 (p=0.37). Older age (OR: 2.4; 95%CI 1.2-4.7), unemployment (OR: 1.75; 95%CI 1.12-2.75) and less than nine years of education (OR: 2.44; 95%CI 1.37-4.33) were independently associated to LT, in a multivariate analysis. CONCLUSION: LT has high prevalence in Mexico, this impact on antiretroviral effectiveness and perhaps on HIV transmission. Policies for HIV-prevention in Mexico need to be modified to reduce LT prevalence including more aggressive strategies of testing.

OBJETIVO: Estimar la prevalencia de diagnóstico tardío (DT) (CD4<200 cel/mm³) de VIH en una clínica en la Ciudad de México entre 2001 y 2008, evaluar cambios en la prevalencia en este periodo y determinar factores de riesgo asociados con el DT. MATERIAL Y MÉTODOS: Mediante un estudio de cohorte transversal de pacientes de VIH se estimó la proporción de pacientes con DT y se compararon sus características demográficas con pacientes sin DT. Se evaluaron los factores de riesgo asociados a DT usando regresión logística. RESULTADOS: Se encontró una prevalencia de DT de 61%, sin cambios entre 2001-2008 (p=0.37). Mayor edad (RM: 2.4; 95%IC 1.2- 4.7), desempleo (RM: 1.75; 95%IC 1.12-2.75) y menos de nueve años de educación (RM: 2.44; 95%IC 1.37-4.33) fueron independientemente asociados a DT. CONCLUSIONES: El DT tiene alta prevalencia en México. Esto impacta en la efectividad de tratamiento antirretroviral y posiblemente en la transmisión del VIH. Deben dirigirse políticas de prevención a reducir el DT mediante estrategias agresivas de diagnóstico.