Symptom screening rules to identify active pulmonary tuberculosis: Findings from the Zambian South African Tuberculosis and HIV/AIDS Reduction (ZAMSTAR) trial prevalence surveys

Background High tuberculosis (TB) burden countries should consider systematic screening among adults in the general population. We identified symptom screening rules to be used in addition to cough >= 2 weeks, in a context where X-ray screening is not feasible, aiming to increase the sensitivity of screening while achieving a specificity of similar to 85%. Methods We used 2010 Zambia South Africa Tuberculosis and HIV/AIDS Reduction (ZAMSTAR) survey data: a South African (SA) training dataset, a SA testing dataset for internal validation and a Zambian dataset for external validation. Regression analyses investigated relationships between symptoms or combinations of symptoms and active disease. Sensitivity and specificity were calculated for candidate rules. Results Among all participants, the sensitivity of using only cough >= 2 weeks as a screening rule was less than 25% in both SA and Zambia. The addition of any three of six TB symptoms (cough < 2 weeks, night sweats, weight loss, fever, chest pain, shortness of breath), or 2 or more of cough < 2 weeks, night sweats, and weight loss, increased the sensitivity to similar to 38%, while reducing specificity from similar to 95% to similar to 85% in SA and similar to 97% to similar to 92% in Zambia. Among HIV-negative adults, findings were similar in SA, whereas in Zambia the increase in sensitivity was relatively small (15% to 22%). Conclusion High TB burden countries should investigate cost-effective strategies for systematic screening: one such strategy could be to use our rule in addition to cough >= 2 weeks.