RESUMEN
En este manuscrito se revisan algunos aspectos básicos de la utilización de regresiones en los estudios epidemiológicos, haciendo énfasis en aquellas aplicadas al estudio de eventos discretos. De esta manera se hace una introducción a los modelos lineales generalizados, cuya estructura es una extensión de una ecuación lineal para analizar desenlaces discretos. De este modo podemos estimar medidas de asociación como la razón de tasas usando la regresión de Poisson, o bien, el riesgo relativo (o la razón de prevalencias) usando la regresión log-binomial. En cada caso es esencial conocer la naturaleza de la variable dependiente, su distribución y reconocer las limitaciones de cada una de las herramientas de análisis.
Some basic aspects about using regressions in epidemiological studies are reviewed. Particularly, this manuscript focused on those applied to the study of discrete events. Generalized lineal models, such as Poisson and log-binomial, have a structure that is an extension of a lineal equation to analyze discrete outcomes. Thus, we can estimate association measures as the incidence rate ratio, using the Poisson regression, or the relative risk (or prevalence ratio), using log-binomial regression. In each case it is essential to know the nature of the dependent variable, as well as, its distribution and recognize the limitations of each analysis tool.
Asunto(s)
Humanos , Modelos Lineales , Distribución Binomial , Distribución de Poisson , Riesgo , Razón de PrevalenciasRESUMEN
Background: Human Herpes Virus 2 (HSV-2) infection has been shown to be significantly associated with several obstetric complications, especially if the infection occurred during the pregnancy. Advocacy for policy formulation and the design of interventions requires local data on the risk factors for incident HSV-2 infection. The aim of this study is to assess HSV-2 sero-incidence among pregnant women in Benin and the effect of socio-demographic factors, HIV status, and HSV-1 status. Study Location, Design and Duration: Pregnant women attending ante-natal clinic in University of Benin Teaching Hospital and Central Hospital, Benin were prospectively recruited. A cross-sectional study was done and baseline data, obtained. The HSV-2 seronegative participants were followed up till the last clinic appointments [the closest appointment to their expected delivery dates (EDD)]. The study took place between November 2011 and December 2012. Methods: On recruitment a structured self-administered questionnaire was used to capture their socio-demographic data. Obstetric data was obtained from the patients’ case notes. Their HSV-1 and HSV-2 serostatuses were determined using an HSV glycoprotein G-based type-specific ELISA technique. Their HIV statuses were also determined. All those who were seronegative for HSV-2 were retested for HSV-2 six months later and/or on their last clinic appointment before the EDD. Incidence rates were calculated per person-years. Data analysis utilized SPSS version 16 software. Results: Out of the 674 participants, 315(46.8%) were HSV-2 seropositive while 359 (53.2%) were seronegative. 15.9% (57) of the HSV-2 sero-negative ones were lost to follow-up, giving a response rate of 84.1%. Seroincidence rate was found to be 17.9 per 100 person-years. There was significant association of seroincidence with younger reproductive age groups, unmarried status, and education below secondary level. Relative Risk (RR) and Incidence rate ratio (IRR) of HSV-2 infection among the HIV-infected cohort were 55.15 [95%CI:17.0-179.1] and 72.37 [95% CI:71.11-73.63] respectively. The RR and IRR among the HSV-1-seronegative cohort were 1.43 [95%CI:0.64-3.17] and 11.62 [95%CI:9.60-13.64] respectively. Conclusion: Seroincidence rate of HSV-2 infection among pregnant women in Benin was found to be 17.9 per 100 person-years. Positive HIV status, young age, unmarried status, and low education level were indicators of increased risk of incident HSV-2 infection.