A new rapid diagnostic test for detection of anti-Schistosoma mansoni and anti-Schistosoma haematobium antibodies.
BACKGROUND
Parasitological methods are widely used for the diagnosis of schistosomiasis. However, they are insensitive, particularly in areas of low endemicity, and labour-intensive. Immunoassays based on detection of anti-schistosome antibodies have the merit of high sensitivity and recently a rapid diagnostic test (RDT), incorporating Schistosoma mansoni cercarial transformation fluid (SmCTF) for detection of anti-schistosome antibodies in blood has been developed. Here, we assessed the diagnostic performance of the SmCTF-RDT for S. mansoni and S. haematobium infections by comparing it with microscopy for egg detection.


METHODS
A cross-sectional survey was carried out in Azaguié, south Côte d'Ivoire. 118 pre-school-aged children submitted two stool and two urine samples, which were subjected to the Kato-Katz and urine filtration methods for the detection of S. mansoni and S. haematobium eggs, respectively. Urine was also subjected to a commercially available cassette test for S. mansoni, which detects circulating cathodic antigen. A finger-prick blood sample was used for the SmCTF-RDT for detection of anti-S. mansoni and anti-S. haematobium antibodies.


RESULTS
The prevalence of both anti-S. mansoni and anti-S. haematobium antibodies was more than three times higher than the prevalence of infection estimated by egg detection under a microscope. Using quadruplicate Kato-Katz as the reference standard for the diagnosis of S. mansoni infection, the sensitivity, negative predictive value (NPV), and positive predictive value (PPV) of the SmCTF-RDT was 75.0%, 84.2% and 22.5%, respectively. When two urine filtrations were considered as the reference standard for the diagnosis of S. haematobium infection, the sensitivity, NPV and PPV of SmCTF-RDT was 66.7%, 94.9% and 5.1%, respectively. The specificity of SmCTF-RDT, when using egg-detection as the reference standard, was estimated to be 34.4%. This low specificity may be a reflection of the relative insensitivity of the direct diagnostic approaches using microscopy.


CONCLUSIONS
The SmCTF-RDT is at least as sensitive as duplicate Kato-Katz and a single urine filtration for detection of S. mansoni and S. haematobium, respectively. Further investigations into the specificity of the test for anti-schistosome antibodies are necessary, but our results suggest that it may be a useful tool for mapping the prevalence of anti-schistosome antibodies in a given population pending intervention.
Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, PO Box, CH-4002 Basel, Switzerland. couljeanvae@yahoo.fr
Jean T
JT
Coulibaly
Eliézer K
EK
N'Goran
Jürg
J
Utzinger
Michael J
MJ
Doenhoff
Emily M
EM
Dawson
D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood*; D001769:Blood / Q000276:immunology; D002675:Child, Preschool; D007560:Cote d'Ivoire; D003430:Cross-Sectional Studies; D003955:Diagnostic Tests, Routine / Q000379:methods*; D005243:Feces / Q000469:parasitology; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007223:Infant; D008297:Male; D008853:Microscopy / Q000379:methods; D010274:Parasitology / Q000379:methods*; D012548:Schistosoma haematobium / Q000276:immunology*; D012550:Schistosoma mansoni / Q000276:immunology*; D012553:Schistosomiasis haematobia / Q000175:diagnosis*; D012555:Schistosomiasis mansoni / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D014556:Urine / Q000469:parasitology
D000909:Antibodies, Helminth