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 serial sputum smears for screening suspects for pulmonary tuberculosis at a rural district hospital in Zambia.

DESIGN

An incremental cost-effectiveness analysis of serial sputum smear examinations for diagnosing pulmonary tuberculosis based on laboratory results collected during 1997 and 1998 in a rural district hospital in Zambia. The cost analysis took a health service provider perspective, and used the ingredients approach. The cost-effectiveness is expressed in terms of the incremental cost per tuberculosis case diagnosed. Relevant information was obtained from various sources, including administrative records, interviews and direct observation.

RESULTS

Of a total of 166 acid-fast bacilli positive suspects who had three sputum smears examined sequentially, 128 (77.1%) were found on the first smear, a further 25 (15%) on the second smear and 13 (7.9%) additional cases were identified on the third smear. The economic analysis shows that the incremental cost of performing a third test, having already done two, increases rapidly with only a small gain in terms of additional cases of tuberculosis identified.

CONCLUSION

A policy of examining two samples should be considered in resource-poor settings, if the remaining steps of the national diagnostic algorithm can be adhered to with respect to smear-negative suspects.