Modelos de inferência causal: análise crítica da utilização da estatística na epidemiologia

The foundations on which the concept of risk has been constructed are discussed. A description of Rubin's model of causal inference, which was first developed in the domain of applied statistics, and later incorporated into a branch of epidemiology, is taken as the starting point. Analysis of the premisses of causal inference brings to light the logical stages in the construction of the concept of risk, allowing it to be understood "from the inside". The abovementioned branch of statistics and epidemiology seeks to demonstrate that statistics can infer causality instead of simply revealing statistical associations; the model gives the basis for estimating that which way be defined as the effect of a cause. Using this procedural distinction between causal inference and association, the model also seeks to differentiate between the epidemiologial dimension of concepts and the merely statiscal dimension. This leads to greater complexity when handing the concepts of interation and coofounding. The redective aspects inherent in this methodological construction of risk are here high lighted. Thus, whether applied to individual or populational inferences, this methodological construction imposes limits that need to be taken into account in its theoretical and pratical application to epidemiology.Discute-se a base de construção do conceito de risco, a partir da descrição do modelo de inferência causal de Rubin, desenvolvido no âmbito da estatística aplicada, e incorporado por uma vertente da epidemiologia. A apresentação das premissas da inferência causal torna visível as passagens lógicas assumidas na construção do conceito de risco, permitindo entendê-lo "por dentro". Esta vertente tenta demonstrar que a estatística é capaz de inferir causalidade ao invés de simplesmente evidenciar associações estatísticas, estimando em um modelo o que é definido como o efeito de uma causa. A partir desta distinção entre procedimentos de inferência causal e de associação, busca-se distinguir também o que seria a dimensão epidemiológica dos conceitos, em contrapartida a uma dimensão simplesmente estatística. Nesse contexto, a abordagem dos conceitos de interação e confusão toma-se mais complexa. Busca-se apontar as reduções que se operam nas passagens da construção metodológica do risco. Tanto no contexto de inferências individuais, quanto populacionais, esta construção metodológica impõe limites que precisam ser considerados nas aplicações teóricas e práticas da epidemiologia

A expansão da hanseníase no nordeste brasileiro

The epidemiological aspects of hanseniasis in Recife from 1960 to 1985 were studied. Clinical-epidemiological records of 3,923 leprosy patients reported to the Secretaria de Saúde do Estado de Pernambuco were reviewed. The cruce as well as the age, sex and type-specific detection rates were calculated. The way the cases were detected and the time elapsed between the appearance of the first symptoms and the disease was analysed. The analysis of the time trend during the observation period showed an increase in the detection rate with time, rising from 5.5 per 100,000 inhabitants in 1960 to 36.1 per 100,000 inhabitants in 1985. The higher frequency of the tuberculoid type of leprosy and the high percentage of patients under 15 might reflect the expansion of the disease in Recife. The decline and the stabilization in the time elapsed between the appearance of the disease and its detection, from 1979 onwards, indicates a more prompt detection and, as a consequence of that, that the rate of detection is approaching the incidence rate. From 1970 to 1985 the most common means of detecting cases of Hanseniasis was through dermatological consultation followed by disease notification. Only 14.2% of the cases were discovered through the surveillance of contacts. The analysis of the epidemiological and operational indicators suggest that the increase in the detection rate over the period from 1960 to 1985 was due both to expansion of the disease and improvement in control measures. The prevalence rate of Hanseniasis in Recife in December 1984 was 2.04 per 100,000 inhabitants; according to the WHO criteria Recife may be considered an area of high endemicity.Caracterizou-se a situação epidemiológica da hanseníase na cidade de Recife, Estado de Pernambuco, Brasil, entre 1960 e 1985, pela análise de 3.923 fichas clínico-epidemiológicas de pacientes notificados à Secretaria de Saúde do Estado de Pernambuco, Brasil. Foram calculados os coeficientes de detecção de casos brutos e específicos por sexo, grupo etário e forma clínica, além de analisados o modo de detecção dos casos e o intervalo de tempo decorrido entre o aparecimento dos sintomas e o diagnóstico de hanseníase. O estudo da tendência temporal do coeficiente de detecção de casos revelou um crescimento progressivo de 5,5:100 000 habitantes em 1960 para 36,1:100 000 habitantes, em 1985. O predomínio da forma tuberculóide e o elevado percentual de menores de 15 anos acometidos pela doença podem estar refletindo a expansão da endemia na cidade do Recife, PE. A diminuição e estabilização do intervalo de tempo decorrido desde o aparecimento dos sintomas até o diagnóstico de hanseníase, a partir de 1979, foram consideradas indicadores da detecção mais precoce dos casos e, conseqüentemente, da aproximação do coeficiente de detecção de casos do coeficiente de incidência. Entre 1970 e 1985, o modo de detecção de casos mais freqüente foi a consulta dermatológica, seguida pela notificação; apenas 14,2% dos casos foram descobertos através da vigilância de comunicantes. A análise dos indicadores epidemiológicos e operacionais sugere que o aumento expressivo do coeficiente de detecção de casos deve ser resultado tanto da expansão da endemia quanto da implementação de algumas das ações de controle. Já o coeficiente de prevalência calculado para a cidade do Recife, em dezembro de 1985, foi de 2,04/mil habitantes, situando-se a cidade como área de alta endemicidade para a hanseníase, pelos critérios da Organização Mundial de Saúde

Factores asociados a la ocurrencia de tuberculosis y su distribución espacial en una ciudad brasileña, 1991-2010

Se buscó identificar los factores asociados a la incidencia de tuberculosis y a la distribución espacial de la enfermedad en Olinda, Pernambuco, entre 1991 y 2010. Para el estudio de los factores asociados a la enfermedad se aplicó la regresión de Poisson y se utilizó la razón de morbilidad estandarizada para el análisis exploratorio espacial. Si bien se observó una reducción en la incidencia media de tuberculosis en Olinda, la tasa se mantiene alta comparada con la media nacional. El mapeo por quinquenios sugiere aumentos hasta 2005, con una caída entre 2006 y 2010, además de la persistencia de alta incidencia en áreas con mayores necesidades socioeconómicas. Las mayores incidencias de tuberculosis estuvieron asociadas a la proporción de analfabetos, de jefes de familia sin ingresos, de domicilios sin abastecimiento de agua, de adultos mayores, a la presencia de más de un caso de retratamiento en el sector censal, y a los domicilios con más de un caso nuevo de tuberculosis. Se concluye que es necesario incorporar el componente espacial a la organización de los servicios de salud y la planificación de la vigilancia epidemiológica de la tuberculosis.This article seeks to identify factors associated with the incidence of tuberculosis and the spatial distribution of the disease in Olinda, Pernambuco, from 1991 to 2010. In order to study the factors associated with the disease, Poisson regression was applied and standardized morbidity ratios were utilized for the spatial exploratory analysis. Although a reduction in the average incidence of tuberculosis in Olinda was observed, the rate remains high in comparison with the national average. Mapping according to five-year periods suggests rate increases until 2005, with a decline between 2006 and 2010 and the persistence of high incidence in areas of greater socioeconomic need. The highest tuberculosis incidence rates were associated in each area with the proportions of illiteracy, of heads of household without income, of households lacking water supply and of older adults, as well as with the presence of cases of retreatment and of households with two or more new cases of tuberculosis. Incorporating a spatial component is key for the organization of health services and the planning of epidemiological surveillance for tuberculosis

Factores asociados a la ocurrencia de tuberculosis y su distribución espacial en una ciudad brasileña, 1991-2010

This article seeks to identify factors associated with the incidence of tuberculosis and the spatial distribution of the disease in Olinda, Pernambuco, from 1991 to 2010. In order to study the factors associated with the disease, Poisson regression was applied and standardized morbidity ratios were utilized for the spatial exploratory analysis. Although a reduction in the average incidence of tuberculosis in Olinda was observed, the rate remains high in comparison with the national average. Mapping according to five-year periods suggests rate increases until 2005, with a decline between 2006 and 2010 and the persistence of high incidence in areas of greater socioeconomic need. The highest tuberculosis incidence rates were associated in each area with the proportions of illiteracy, of heads of household without income, of households lacking water supply and of older adults, as well as with the presence of cases of retreatment and of households with two or more new cases of tuberculosis. Incorporating a spatial component is key for the organization of health services and the planning of epidemiological surveillance for tuberculosis.Se buscó identificar los factores asociados a la incidencia de tuberculosis y a la distribución espacial de la enfermedad en Olinda, Pernambuco, entre 1991 y 2010. Para el estudio de los factores asociados a la enfermedad se aplicó la regresión de Poisson y se utilizó la razón de morbilidad estandarizada para el análisis exploratorio espacial. Si bien se observó una reducción en la incidencia media de tuberculosis en Olinda, la tasa se mantiene alta comparada con la media nacional. El mapeo por quinquenios sugiere aumentos hasta 2005, con una caída entre 2006 y 2010, además de la persistencia de alta incidencia en áreas con mayores necesidades socioeconómicas. Las mayores incidencias de tuberculosis estuvieron asociadas a la proporción de analfabetos, de jefes de familia sin ingresos, de domicilios sin abastecimiento de agua, de adultos mayores, a la presencia de más de un caso de retratamiento en el sector censal, y a los domicilios con más de un caso nuevo de tuberculosis. Se concluye que es necesario incorporar el componente espacial a la organización de los servicios de salud y la planificación de la vigilancia epidemiológica de la tuberculosis

Tuberculose no Brasil: construção de um sistema de vigilância de base territorial

OBJECTIVE: To analyze the occurrence of tuberculosis and to identify variables that define situations of collective risk that determine the spatial distribution of the disease, as backing for implementing a territory-based surveillance system for tuberculosis control. METHODS: This was an ecological study performed in Olinda, a municipality in the metropolitan region of Recife, State of Pernambuco, between 1996 and 2000. The median number of notified tuberculosis cases in each census tract served as the cutoff point for characterizing areas of high and low transmission. A logistic regression model using this response variable allowed odds ratios for some socioeconomic variables from the 2000 demographic census and other covariates related to the transmission of the disease to be estimated. RESULTS: Tuberculosis in Olinda presented high incidence rates during the study period (average of 111 cases per 100,000 inhabitants). Significant associations with the occurrence of tuberculosis were found for the variables of average number of inhabitants per household (OR=2.2; 95% CI: 1.3; 3.6); existence of families with more than one case during the study period (OR=5.1; 95% CI: 2.3; 11.3); and presence of cases of retreatment (OR=6.8; 95% CI: 2.7; 17.1). The census tract where the latter two events occurred accounted for 45% of the total number of cases during the study period, while representing only 28% of the population of Olinda. CONCLUSIONS: The two explanatory covariates that were strongly associated with higher incidence rates of the disease are events that need to be carefully monitored at a local level by the tuberculosis surveillance system. Simply by mapping out retreatment cases and households with more than one case, attention could be focused on small areas with high priority for intensive intervention, thus facing up to the tuberculosis problem.OBJETIVO: Analisar a ocorrência da tuberculose, identificando variáveis definidoras de situações coletivas de risco que determinam sua distribuição espacial, como subsídio à implantação de um sistema de vigilância de base territorial para controle da tuberculose. MÉTODOS: Estudo ecológico realizado no período 1996-2000, em Olinda, município da região metropolitana do Recife, PE. A mediana do número de casos de tuberculose, notificados por setor censitário, serviu como ponto de corte para caracterização das áreas de alta e baixa transmissão. Um modelo de regressão logística, utilizando essa variável resposta, permitiu estimar as "odds-ratio" de algumas variáveis socioeconômicas do Censo Demográfico de 2000 e de outras co-variáveis relacionadas com a transmissão da doença. RESULTADOS: A tuberculose em Olinda apresentou altas taxas de incidência no período (média de 111 casos por 100.000 habitantes). Verificou-se que são significativamente associadas à ocorrência da tuberculose, as variáveis: média de moradores por domicílio (OR=2,2; IC 95%: 1,3; 3,6); existência de famílias com mais de um caso no período (OR=5,1; IC 95%: 2,3; 11,3); e presença de casos de retratamento (OR=6,8; IC 95%: 2,7; 17,1). Setores censitários com a ocorrência desses dois últimos eventos concentraram 45% do total de casos do período, representando apenas 28% da população do município. CONCLUSÕES: Duas das três variáveis explicativas associadas a maiores taxas de incidência da doença são informações que devem ser monitorizadas, em nível local, pelo sistema de vigilância da tuberculose. O simples mapeamento de casos de retratamento e de domicílios com ocorrência de repetidos casos, permitiria refinar o foco de atenção em micro-áreas prioritárias para intervenções intensivas, como forma de enfrentar o problema da tuberculose

Análise espacial dos determinantes socioeconômicos dos homicídios no Estado de Pernambuco

OBJECTIVE: To investigate the association between homicide rates and socio-economic variables taking into account the spatial site of the indicators. METHODS: An ecological study was conducted. The dependent variable was the rate of homicides among the male population aged 15 to 49 years, residing in the districts of the State of Pernambuco from 1995 to 1998. The independent variables were an index of the living conditions, per capita family income, Theil inequality index, Gini index, average income of the head of the family, poverty index, rate of illiteracy, and demographic density. The following techniques were used in the analysis: a spatial autocorrelation test determined by the Moran index, multiple linear regression, a spatial regression model (CAR) and a generalized additive model for the detection of spatial trend (LOESS). RESULTS: The illiteracy and the poverty index explained 24.6% of the total variability of the homicide rates and there was an inverse relationship. Moran´s I statistics indicated spatial autocorrelation between municipalities. The multiple linear regression model best fitted for the purposes of this study was the Conditional Auto Regressive (CAR) model. The latter confirmed the association between the poverty index, illiteracy and homicide rates. CONCLUSIONS: The inverse association observed between socio-economic indicators and homicides may be expressing a process that propitiates improvement in living conditions and that is linked predominantly to conditions that generate violence, such as drug traffic.OBJETIVO: Investigar a associação entre variáveis socioeconômicas e taxas de homicídio, considerando a localização espacial dos indicadores. MÉTODOS: Utilizou-se o método de estudo ecológico. A variável dependente foi taxa de homicídio da população masculina de 15 a 49 anos, residente nos municípios do Estado de Pernambuco, em 1995 a 1998. As variáveis independentes referem-se a: índice de condições de vida, renda familiar per capita, desigualdade de Theil, índice de Gini, renda média do chefe de família, índice de pobreza, taxa de analfabetismo, densidade demográfica.Utilizou-se teste de correlação espacial determinado pelo Índice de Moran, regressão múltipla, Conditional Auto Regressive (CAR) e a função Loess, como modelo de detecção de tendência especial. RESULTADOS: Os indicadores taxa de analfabetismo e índice de pobreza explicaram 24,6% da variabilidade total das taxas de homicídio, cuja associação foi inversa. O índice de Moran revelou autocorrelação espacial entre os municípios. O modelo de regressão espacial que melhor se adequou ao estudo foi o CAR, que confirmou a associação entre índice de pobreza, analfabetismo e homicídio. CONCLUSÕES: A relação inversa observada entre os indicadores socioeconômicos e homicídios pode expressar determinado processo que propicia melhoria das condições de vida, e está atrelado predominantemente a condições geradoras de violência, como a do tráfico de drogas

Effectiveness of screening for tuberculosis in HIV: a pragmatic clinical trial

OBJECTIVE: To verify the effectiveness of screening for tuberculosis (TB) on all-cause mortality and tuberculosis cases in newly diagnosed HIV-infected patients through a clinical algorithm based on recommendations of the World Health Organization. METHODS: From March 2014 to April 2016, a pragmatic randomized clinical trial was conducted with newly diagnosed and TB-free HIV-infected adults undergoing antiretroviral therapy for up to one month at a major tertiary hospital for HIV in the state of Pernambuco, Brazil. Participants were randomized into intervention and control groups using an automatically-generated random list, and followed-up for at least 6 months. The intervention group was screened for TB at hospital admission and at every follow-up visit through a series of questions addressing TB-related symptoms (cough, fever, night sweating, and weight loss). Patients presenting with any of these symptoms were referred to a pulmonologist and underwent sputum smear microscopy, sputum culture, and rapid molecular testing (GeneXpert). When at least one test result came back positive, TB treatment was initiated. In turn, if patients tested negative but presented with severe clinal symptoms, TB preventive treatment was initiated. Screening for TB was not performed systematically in the control group. The primary outcome assessed in this study was death from all causes, and secondary outcomes included sensitivity and specificity of this screening test, as well as its detection time. RESULTS: This study evaluated 581 patients, 377 in the intervention group (64.9%) and 204 in the control group (35.1%). In total, 36 patients died during the follow-up period. Of these, 26 (6.9%) were from the intervention group, reaching a cumulative mortality coefficient of 69 per 1,000 inhabitants, and 10 (4.9%) from the control group (p = 0.341), with a cumulative mortality coefficient of 49 per 1,000 inhabitants (p = 0.341)

Incidence and risk factors for tuberculosis in people living with HIV: cohort from HIV referral health centers in Recife, Brazil.

OBJECTIVE: To identify the incidence of and risk factors for tuberculosis in people living with HIV (PLHIV). DESIGN: Observational, prospective cohort study. METHODS: A total of 2069 HIV-infected patients was observed between July 2007 and December 2010. The Kaplan-Meier method was used to estimate the probability of survival free of tuberculosis, and Cox regression analysis to identify risk factors associated with the development of tuberculosis. RESULTS: Survival free of tuberculosis (TB) was 91%. The incidence rate of tuberculosis was 2.8 per 100 persons/years. Incidence of tuberculosis was higher when subjects had CD4 cell count <200 cells/mm(3); were not on antiretroviral therapy; in those who had, a body mass index <18.5 kg/m(2), anemia (or were not tested for it), were illiterate or referred previous tuberculosis treatment at entry into the cohort. Those not treated for latent TB infection had a much higher risk (HR = 7.9) of tuberculosis than those with a negative tuberculin skin test (TST). Having a TST≥5 mm but not being treated for latent TB infection increased the risk of incident tuberculosis even in those with a history of previous tuberculosis. CONCLUSIONS: Preventive actions to reduce the risk of TB in people living with HIV should include an appropriate HAART and treatment for latent TB infection in those with TST≥5 mm. The actions towards enabling rigorous implementation of treatment of latent TB infection and targeting of PLHIV drug users both at the individual and in public health level can reduce substantially the incidence of TB in PLHIV

Microcephaly in Pernambuco State, Brazil: epidemiological characteristics and evaluation of the diagnostic accuracy of cutoff points for reporting suspected cases.

The increase in the number of reported cases of microcephaly in Pernambuco State, and Northeast Brazil, characterized an epidemic that led the Brazilian Ministry of Health to declare a national public health emergency. The Brazilian Ministry of Health initially defined suspected cases as newborns with gestational age (GA) ≥ 37 weeks and head circumference (HC) ≤ 33cm, but in December 2015 this cutoff was lowered to 32cm. The current study aimed to estimate the accuracy, sensitivity, and specificity of different cutoff points for HC, using ROC curves, with the Fenton and Intergrowth (2014) curves as the gold standard. The study described cases reported in Pernambuco from August 8 to November 28, 2015, according to sex and GA categories. The Fenton and Intergrowth methods provide HC growth curves according to GA and sex, and microcephaly is defined as a newborn with HC below the 3rd percentile in these distributions. Of the 684 reported cases, 599 were term or post-term neonates. For these, the analyses with ROC curves show that according to the Fenton criterion the cutoff point with the largest area under the ROC curve, with sensitivity greater than specificity, is 32cm for both sexes. Using the Intergrowth method and following the same criteria, the cutoff points are 32cm and 31.5cm for males and females, respectively. The cutoff point identified by the Fenton method (32cm) coincided with the Brazilian Ministry of Health recommendation. Adopting Intergrowth as the standard, the choice would be 32cm for males and 31.5cm for females. The study identified the need to conduct critical and on-going analyses to evaluate cutoff points, including other characteristics for microcephaly case definition