Rapid diagnosis of Bancroftian filariasis by acridine orange staining of centrifuged parasites.
A rapid diagnostic test for detection of microfilaremia using a microhematocrit tube precoated with acridine orange (the Quantitative Buffy Coat [QBC] tube) was compared with a conventional 50 microliters-thick blood film (TF) in 119 volunteers in an area of Recife, Brazil that was endemic for Wuchereria bancrofti. Both the QBC and the TF techniques were 100% specific, and thus positive predictive values were equal at 100% for each technique in all subjects studied. Both techniques had equal negative predictive values of 100% in subjects with microfilarial counts > 100 per milliliter (mf/ml). Counts < 20 mf/ml are below a cutoff equal to the calculated limit of sensitivity of each of the two techniques. For those individuals with counts between 20 and 99 mf/ml, negative predictive values were, for practical diagnostic purposes, equivalent at 97.5% for the QBC technique and 99.0% for the TF. Because the QBC technique has predictive values as high as conventional TF, the convenience and rapidity of the technique will make the QBC technique a desirable alternative diagnostic method in those clinical settings where the equipment is available. A positive result will be available in less than six min after obtaining the specimen in individuals with counts < 100 mf/ml, and individuals with lower or no microfilaremia will have a result within 6-12 min.
D000165:Acridine Orange; D000818:Animals; D002498:Centrifugation; D004605:Elephantiasis, Filarial / Q000097:blood / Q000175:diagnosis* / Q000469:parasitology; D005374:Filtration; D006801:Humans; D008842:Microfilariae / Q000254:growth & development / Q000302:isolation & purification; D011237:Predictive Value of Tests; D013194:Staining and Labeling; D014958:Wuchereria bancrofti / Q000254:growth & development / Q000302:isolation & purification*
D000165:Acridine Orange