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

Abstract

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<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<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 %.