Diagnosing tuberculosis in a resource-poor setting: the value of a trial of antibiotics

Trans R Soc Trop Med Hyg. 1997 Jul-Aug;91(4):422-4. doi: 10.1016/s0035-9203(97)90264-9.


Diagnosis of smear-negative but culture-positive pulmonary tuberculosis in resource-poor settings is difficult. To determine the value of assessing response to a trial of antibiotics in the identification of patients with positive cultures but negative Ziehl-Neelsen (ZN) smears, we compared clinicians' diagnoses with culture in 334 consecutive adults 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 the smear-negative but culture-positive cases were correctly identified by failing to respond to a broad spectrum antibiotic. The remainder responded to therapy and were discharged. Diagnostic sensitivity therefore increased to 80%, but specificity fell to 78%. A more rigorous algorithm may improve diagnosis of smear-negative pulmonary tuberculosis in resource-poor settings.

MeSH terms

  • Adult
  • Antibiotics, Antitubercular / therapeutic use*
  • Cross-Sectional Studies
  • Humans
  • Medically Underserved Area
  • Sensitivity and Specificity
  • South Africa
  • Sputum / microbiology*
  • Tuberculosis, Pulmonary / diagnosis*
  • Tuberculosis, Pulmonary / drug therapy


  • Antibiotics, Antitubercular