HIV infection and chronic chest disease as risk factors for bacterial pneumonia: a case-control study

To investigate risk factors for severe acute pneumonia in South African gold miners.

An inclusive case-control study drawn from a predefined cohort of 4762 miners of known HIV status. Cases were defined by hospital admission meeting the clinical and radiological case definitions for pneumonia during 1998. Controls were randomly selected from the starting cohort. Considered risk factors were: HIV infection, smoking, age, occupation, previous tuberculosis, and chronic premorbid chest disease caused by post-tuberculous lung disease or silicosis (International Labour Office grades 1/0 and above) defined from routine screening radiographs taken before the start of the study.

There were 109 cases and 400 controls. HIV infection [odds ratio (OR) 31.6], previous tuberculosis (OR 2.4), and an abnormal premorbid radiograph (OR 2.8) were each significantly more prevalent in cases than controls, whereas other variables were not. On multivariate analysis, HIV infection [OR 30.7, 95% confidence interval (CI) 12.1-78.1] and an abnormal premorbid radiograph (OR 2.3, 95% CI 1.1-4.8) remained significant risk factors. Median CD4 cell counts in HIV-positive cases with and without abnormal premorbid radiographs were 185 and 162 x 106/l, making confounding between chronic chest disease and the extent of immunocompromise an unlikely explanation for this association.

HIV infection and an abnormal premorbid chest radiograph are both strong risk factors for pneumonia in miners. Pre-existing chronic chest disease may be an important risk factor for HIV-associated pneumonia in other populations, and if so, is an additional indication for considering antibiotic prophylaxis in HIV-positive individuals.