An assessment of radial haemolysis in the detection of rubella antibody

SUMMARY The results obtained by radial haemolysis in the detection of antibodies to rubella virus compared well with those obtained by haemagglutination inhibition. Radial haemolysis is unaffected by non-specific inhibitors. The sera do not therefore require pretreatment and the results are less equivocal. Radial haemolysis appears to be as sensitive as immunofluorescence and floatation centrifugation. It is possible to examine large numbers of sera with a considerable saving of time compared with the traditional haemagglutination technique. Rheumatoid factor may cause inter-ference in radial haemolysis. Immune sera may be recorded as non-immune. This interference can be removed by 2-mercaptoethanol or reduced by heating sera at 60°C for 20 minutes. Antibodies to rubella virus are most commonly demonstrated using the haemagglutination inhibition (HI) test. This test is relatively simple but involves pretreatment of the sera to remove nonspecific inhibitors and absorption to remove agglutinins to the erythrocytes. It is subject to some variability both within and between laboratories and the whole pro-cedure must be carefully controlled to minimise such variation. Although the test is sensitive some difficulty arises in interpreting the significance of low HI titres because of the possibility of interference from residual nonspecific inhibitors. Schild et al. (1975) described the use of radial haemolysis (RH) for influenza virus. Its application to the detection of antibodies to rubella virus has been described recently by Strannegard et al. (1975), Skaug et al. (1975), and Grillner and Strannegard (1976). It depends on the lysis of erythrocytes coated with haemagglutinin by complement in the presence of specific antibody. The method they described was simple to perform and both sensitive and reprodu-cible. It should therefore be suitable for the screening of large numbers of sera. In this paper we compare the rubella antibody results obtained by the HI and RH techniques. Material and methods Altogether 1182 sera were examined: 1089 were routine sera submitted to the laboratory for rubella estimations (during 1976-77) and were mainly fro