[Predictive value of positive and negative results of the Widal and Felix test for typhoid fever in general practice in Niamey].

BACKGROUND

Typhoid is a common reason for seeking medical care in general practice in the developing countries, Use of the Widal and Felix test is frequent in this setting. The purpose of this study carried out in private general medicine clinics in Niamey, Niger was to determine the incidence of typhoid and the predictive value of positive and negative results of the Widal test.

METHODS

We used low published values of sensitivity (67.9%) and specificity (93.8%). Estimation of the incidence of typhoid was based on reports made to the national health information system of Niger by 3 private clinics in Niamey.

RESULTS

A total of 1725 persons attended the clinics between 1/12/07 and 31/01/08, including 311 presenting nonspecific signs suggesting typhoid, i.e., at least fever and headache, and 172 presenting typhoid. The incidence was 9.97% in attendees overall and 55.31% in attendees with nonspecific evocative signs. The positive predictive value of the Widal and Felix test was 53.81% and the negative predictive value was 96.35% in attendees overall and 93.13% and 70.25% respectively in patients with clinical signs.

CONCLUSIONS

Other diagnostic modalities such as PCR, coproculture, and hemoculture can be proposed, but are not available in this setting. The positive predictive value of the Widal test among patients with nonspecific signs suggesting typhoid is high. While not negligible, the negative predictive value in this high-incidence group is relatively low and should indicate monitoring.