Etiology of Pulmonary Infections in Predominantly HIV-infected Adults with Suspected Tuberculosis, Botswana

Setting: In countries with high HIV rates, diagnosis of lower respiratory disease etiology is both challenging and clinically important.

Objective: To determine the etiology of lower respiratory tract disease among persons with suspected tuberculosis (TB) and abnormal chest X-rays in a setting with very high HIV seroprevalence.

Design: Cross-sectional prevalence data from a prospective cohort of predominantly hospitalized adults with suspected TB in Botswana, January-December 1997.

Results: Of 229 patients, 86% were HIV-positive and 71% had a pathogen identified. TB was confirmed in 52%, 17% had acute mycoplasma pneumonia, 3% had Pneumocystis carinii, 27% grew a bacterial pathogen from sputum and 8% from blood. Ninety-four per cent of TB diagnoses were made through expectorated sputum and only 5% of TB cases were diagnosed by sputum induction alone. Polymerase chain reaction (PCR) for Mycobacterium tuberculosis had positive and negative predictive values of 94% and 59%, respectively. Male sex, cough < 2 weeks, and tuberculin skin test > or = 5 mm were independently associated with culture-positive TB among persons with negative acid-fast bacilli smears. Co-infection with two or more pathogens occurred in 25%.

Conclusions: Mycoplasma pneumoniae infection was quite common despite clinical suspicion of TB, and sputum induction and PCR did not significantly improve our ability to diagnose TB, although clinical presentation had some predictive value.