DRUG-RESISTANT TUBERCULOSIS - LABORATORY ISSUES - WORLD-HEALTH-ORGANIZATION RECOMMENDATIONS

There is a suggestion that drug resistance rates decreased in developi ng countries over the period 1962-85, while recent data suggest that r esistance may be increasing. The initial decrease in resistance appear s to be associated with well-functioning National Tuberculosis Control Programmes (NTP), while the recently observed increase may be due eit her to understaffed, resource-poor programmes or to the effect of the HIV epidemic, or to both. It is possible that the HIV epidemic may ove rwhelm the NTP, resulting in decreased programme efficiency and ultima tely increased drug resistance. Resistance surveillance appears to be a good measure of programme efficiency. For research purposes, primary drug resistance surveys should be done on a sample of relevant patien ts which includes and distinguishes between HIV-positive and HIV-negat ive patients. At this time, there is not enough information to warrant a recommendation regarding HIV testing of TB patients for surveillanc e purposes. In order for resistance surveys to be relevant from the pu blic health perspective, one must know the proportion of patients pres enting for treatment having previously received treatment. The meaning ful denominator for drug resistance surveys from the programme evaluat ion perspective should be the number of patients presenting for treatm ent. For initial drug resistance surveys the measurement should be the number of people never having received prior TB treatment with resist ant bacilli, divided by the number of new patients presenting for trea tment. For acquired resistance, one should look at all patients who be gin treatment with susceptible bacilli who become resistant 6 months l ater.