Schistosomiasis: assessment of the sensitivity, specificity and reproducibility of serological methods for the diagnosis of schistosomiasis in Nigeria.

Three groups of sera were tested by indirect fluorescent antibody (IFA), complement fixation (CF) and counter-current immunoelectrophoresis (CCIE) techniques; 56 (10.1%) of 554 sera from Nigerians were anticomplementary and so could not be tested by the CF. Crude antigen extract of adult Schistosoma mansoni was used in the CF and CCIE tests and cercarial antigen in the IFA test. IFA was the most sensitive test and CF the most specific. The reproducibility of both these tests was good. The CCIE was the least sensitive and specific, and its reproducibility was poor. The IFA test was the most suitable for Nigerian conditions. Cross-reactions to S. haematobium antibodies were consistently present in all three tests and it was not possible to differentiate serologically S. mansoni from S. haemotobium. The interpretations of the results presented some difficulties because of the frequency of cross-reactions and false-positives, but the data fell within the infection prevalence rate of 50% reported earlier from south-western Nigeria. The IFA test was more specific and is considered ideal for serodiagnosis.