Smear-negative, culture-positive pulmonary tuberculosis among patients with chronic cough in Cotonou, Benin.

SETTING

The main tuberculosis (TB) centre in Benin, West Africa, where only 2% of adult pulmonary TB cases are sputum smear-negative, all other pulmonary cases being smear-positive.

OBJECTIVES

To assess the burden of smear-negative, culture-positive pulmonary TB among TB suspects in Cotonou, and to estimate the total number of non-smear-positive TB cases at country level.

DESIGN

For 1 year, one morning sputum culture was performed for every TB suspect (cough lasting >3 weeks, as defined in Benin's national guidelines) with three negative sputum smears (fluorescence technique).

RESULTS

Of 214 TB suspects for whom culture was performed, only 22 smear-negative, culture-positive cases were identified. During the same period, 831 sputum smear-positive cases were diagnosed. Culture therefore contributed only 2.6% of the total number of bacteriologically proven cases.

CONCLUSION

These results show the relatively low input of culture in TB diagnosis among chronic coughers in Cotonou, Benin, and demonstrates that the expected number of non-smear-positive TB cases in Benin is probably much lower than the World Health Organization's current annual estimates.