Complement-fixation test for rotavirus detection: comparison and analysis of different methods to reduce anti-complementary activity of some specimens

The complement-fixation test may be used to detect rotaviral antigens directly in clinical specimens. However, a certain number of specimens tested for human rotaviruses by the complementfixation test show an anti-complementary activity. By comparing eight techniques we analysed this anti-complementary activity and identified the best method for its reduction. Pretreatment of clarified supernatant of stool suspensions by some methods resulted in a reduction of anti-complementary activity, without reducing the sensitivity of the method. Clarified supernatants of 8 36 (22.2%) specimens were anti-complementary; this anti-complementary activity was best removed by absorption with fetal calf serum or calf albumin. Such treatment offers practical means of increasing the specificity of complement-fixation test. Some observations suggest that the anti-complementary activity of stool suspensions may be frequently due to the presence of one or more chelating agents that may be in faecal specimens.