Hotting-up the complement-fixation test

Abstract

A detailed investigation into the effect of modifying the incubation temperature of the complement-fixation (CF) test is described. For varicella-zoster virus cytomegalovirus and rubella virus, increasing the incubation temperature progressively increased the sensitivity of the CF test to reach a maximum at 15 degrees C, at which temperature the geometric mean titre of seropositive samples was significantly greater than that found at 4 degrees C. For these three viruses, each serum shown to contain IgG antibodies by ultrasensitive radioimmunoassay procedures was detected by CF following incubation at 15 degrees C. No false-positive reactions occurred at 15 degrees C, but it was our impression that anticomplementary activity was enhanced at this temperature. Significant increases in antibody titre at 15 degrees C were also seen when measles virus, respiratory syncytial virus, adenovirus and Mycoplasma pneumoniae were employed as CF antigens. The results demonstrate that the CF test should be performed at 15 degrees C if optimum sensitivity is to be achieved. The ability of the test to detect significant rises in antibody titre was not impaired at the higher incubation temperature.