DIAGNOSING TUBERCULOSIS IN A RESOURCE-POOR SETTING - THE VALUE OF A TRIAL OF ANTIBIOTICS

Diagnosis of smear-negative but culture-positive pulmonary tuberculosi s in resource-poor settings is difficult. To determine the value of as sessing response to a trial of antibiotics in the identification of pa tients with positive cultures but negative Ziehl-Neelsen (ZN) smears, we compared clinicians' diagnoses with culture in 334 consecutive adul ts with suspected tuberculosis in rural South Africa; 142 patients (43 %) had culture-positive pulmonary tuberculosis. Diagnosis by ZN smear alone was insensitive (61%) but highly specific (94%). Only half of th e smear-negative bur culture-positive cases were correctly identified by failing to respond to a broad spectrum antibiotic. The remainder re sponded to therapy and were discharged. Diagnostic sensitivity therefo re increased to 80%, but specificity fell to 78%. A more rigorous algo rithm may improve diagnosis of smear-negative pulmonary tuberculosis i n resource-poor settings.