DIAGNOSIS OF PALUDISM BY THICK-FILM AND QBC - COMPARATIVE-STUDY OF BOTH TECHNIQUES

BACKGROUND: The diagnosis of paludism is important because of the seve rity of the clinical picture caused by Plasmodium falciparum, the incr easing number of travellers to endemic zones and the emigration from t hese zones. A comparative study of the QBC techniques (staining with a cridin orange and observation with ultraviolet light) and the thick fi lm with Giemsa staining was carried out.METHODS: The QBC and thick fil m were performed parallely for 17 months in a total of 623 samples per taining to subjects from endemic zones of paludism (emigrants, immigra nts and travellers). RESULTS: Of the 623 samples studied 49 were posit ive for paludism by both techniques. Ten were positive with only the t hick film and six were positive only with QBC. The sensitivity of QBC versus thick film was 83 % and specificity 98.9 %. The time used to de termine diagnosis with the QBC technique ranged from 6 to 12 minutes f rom withdrawal of the sample, while with the thick film the time spent was more than 2 hours. The cases positive by thick film and negative with QBC corresponded to patients with very low parasitation. The inte nsity of parasitation was difficult to determine quantitatively by QBC . CONCLUSIONs: Although the QBC technique has the advantage of speed i t is inexact with respect to the quantification of parasitemia. Moreov er, it is less sensitive than the thick film in patient with very low parasitations and cannot thus substitute the thick film.