An incremental cost-effectiveness analysis of the first, second and third sputum examination in the diagnosis of pulmonary tuberculosis

SETTING: St. Francis Hospital in Katete District, Eastern Province, Zambia. OBJECTIVE: To compare the incremental cost-effectiveness of examining seria l sputum smears for screening suspects for pulmonary tuberculosis at a rura l district hospital in Zambia. DESIGN: An incremental cost-effectiveness analysis of serial sputum smear e xaminations for diagnosing pulmonary tuberculosis based on laboratory resul ts collected during 1997 and 1998 in a rural district hospital in Zambia. T he cost analysis took a health service provider perspective, and used the i ngredients approach. The cost-effectiveness is expressed in terms of the in cremental cost per tuberculosis case diagnosed. Relevant information was ob tained from various sources, including administrative records, interviews a nd direct observation. RESULTS: Of a total of 166 acid-fast bacilli positive suspects who had thre e sputum smears examined sequentially, 128 (77.1%) were found on the first smear, a further 25 (15%) on the second smear and 13 (7.3%) additional case s were identified on the third smear. The economic analysis shows that the incremental cost of performing a third test, having already done two, incre ases rapidly with only a small gain in terms of additional cases of tubercu losis identified. CONCLUSION: A policy of examining two samples should be considered in resou rce-poor settings, if the remaining steps of the national diagnostic algori thm can be adhered to with respect to smear-negative suspects.