A comparison of newer tests for the diagnosis of onchocerciasis

Samples of human serum, skin and urine, collected in Cameroon, were used to assess the value of some newer methods for the diagnosis of onchocerciasis. Parasite DNA was detected in skin snips and urine by PCR, and parasite antigen was detected in serum and urine by immunoblotting. Serum concentrations of IgG4 antibodies reacting with recombinant Onchocerca volvulus antigens (OC3.6 and OC9.3) were also measured, using an ELISA. The PCR-based tests of skin snips and the serological tests for antigen and antibody tests showed higher sensitivities (90%-100%) than the urine PCR (14%) or the urine antigen test (68%). Although antibody detection is much easier to perform than tests based on PCR or antigen detection, the latter have an advantage in that they are only positive in people with current infections. Thus, antibody testing may be more useful for screening populations for infection or exposure to O. volvulus, whereas PCR and antigen testing are potentially more useful for diagnosis of infections in individuals and for monitoring the success of therapy.