Studies of case-finding for pulmonary tuberculosis in outpatients at 4 district hospitals in Kenya

This investigation is the sixth in a series of case-finding studies in Kenya. It explores the potential for case-finding by the identification of tuberculosis suspects (individuals with a cough for 1 month or more) through careful screening of general outpatients attending 4 district hospitals for the first time. Of 2299 suspects identified among 87 845 new outpatients attending the hospitals, 4.7% had culture-positive pulmonary tuberculosis, 3.6% having sputum positive on smear as well. In the 3 hospitals with radiographic facilities, 1.3% of suspects (whose sputum was negative on culture) were considered on review of their clinical history and chest radiograph by an independent assessor to have radiographically active tuberculous lesions and a further 2.5% to have inactive lesions. The proportion of bacteriologically positive cases per 1000 of the general population aged 6 years or more decreased as the distance of their homes from the hospital increased (P less than 0.001 for the trend). However, the proportion of cases per 1000 of the suspects identified increased as the distance of their homes from the hospital increased (P less than 0.001 for the trend). History of cough for between 1 and 12 months was the most useful factor for the identification of cases of tuberculosis among the suspects, and would have identified 92% of the smear-positive cases from the examination of 70% of the suspects; a history of weight loss identified 84% of the smear-positive cases from the examination of 64% of the suspects. A history of weight loss and/or a history of cough for between 1 and 12 months would have detected all the smear-positive cases from the examination of 89% of the suspects. The proportion of bacteriologically positive cases in the younger suspects aged 9-32 years (who had been eligible for a mass BCG campaign) was greater among the non-vaccinated than among the vaccinated suspects, 4.9% and 2.3% respectively (P=0.04), implying protection from vaccination of the order of 50%.