Impact of resistance to anti-tuberculosis drugs on treatment outcome using World Health Organization standard regimens.

We compared treatment outcome in 410 patients with drug-susceptible tuberculosis (DS-TB) and 150 patients with drug-resistant tuberculosis (DR-TB) among 560 adult patients (> or = 15 years old) notified with smear-positive pulmonary tuberculosis between July 1997 and June 1998 in the West Province of Cameroon and treated with World Health Organization (WHO) standard regimens under field conditions. Information on treatment outcome was collected for all smear-positive TB patients having a positive culture with drug susceptibility tests performed for isoniazid, rifampicin, ethambutol and streptomycin. Treatment outcome was recorded as cured, completed treatment, failed, defaulted, died or transferred out, 332 of the 410 patients (81%) with DS-TB were cured, compared to 109/150 (72.7%) patients with DR-TB (odds ratio [OR] = 0.62, 95% confidence interval [CI] 0.40-0.99). Seven patients (1.7%) failed treatment in the DS-TB group vs. 9 (6.0%) in the DR-TB group (OR = 3.67, 95% CI 1.23-11.18). No significant difference was found in rates of death, default or transfer. Sputum smear conversion at the end of the intensive treatment phase was observed in 78.8% of the cases, drug resistance having no effect on the conversion rate. After adjusting for age, sex and resistance, the death rate was higher in patients also infected with human immunodeficiency virus (HIV). In TB cases with multidrug resistance, standard regimens result in unacceptably high failure rates (26.1%). For all other drug-resistant forms of TB, rifampicin-based short-course chemotherapy gave satisfactory results. The death toll in the West Province seems due to HIV co-infection rather than to TB alone. To prevent development of drug-resistance, the proportion of defaulters must be decreased and prevention and control strategies endorsed by the WHO and the International Union Against Tuberculosis and Lung Disease must be implemented nation-wide.