SHOULD WE TAKE A HISTORY OF PRIOR TREATMENT, AND CHECK SPUTUM STATUS AT 2-3 MONTHS WHEN TREATING PATIENTS FOR TUBERCULOSIS

SETTING: Pinetown, South Africa (1975-1983). OBJECTIVE: To determine t he value of previous treatment history and sputum smear examination at 2-3 months in predicting treatment failure and relapse in tuberculosi s patients treated with four drugs given twice weekly for six months u nder direct observation. DESIGN: Four cohort studies among 562 ambulan t adults with culture positive pulmonary tuberculosis, designed to tes t the effectiveness of isoniazid 600-900 mg, rifampicin 600 mg, pyrazi namide 2-3 g, and streptomycin 1-2 g, given twice weekly. The same dru g regimen was given to all patients irrespective of previous treatment history. Therapy was not changed if smears remained positive at 2-3 m onths. RESULTS: Positive predictive values of a history of previous tr eatment for a positive smear at 2-3 months (18.3%), treatment failure (5.2%), and relapse (9.4%) were poor. Although patients with positive smears at 2-3 months were more likely to fail therapy than patients wi th negative smears (relative risk = 4.5, 95% Confidence Interval [CI]: 1.6-12.8), positive predictive value for treatment failure was only 1 2.5%. Although relapse was more frequent in patients with positive sme ars than those with negative smears (9.7% vs 6.2%; P = 0.4), most pati ents who relapsed had been smear negative at 2-3 months (18/21). CONCL USION: A four-drug rifampicin-containing regimen can safely be given t wice weekly under direct observation to both new and retreatment cases , and the 2-3 month smear examination can safely be omitted.