Detection of rubella haemagglutination-inhibition (HAI) and virus-specific IgM antibody using trypsin-treated human group O erythrocytes in the HAI test.

Abstract

SUMMARY The modification of the standard rubella haemagglutination-inhibition (HAl) test using trypsin-treated human group 0 erythrocytes instead of chick erythrocytes was evaluated. In a comparative study we found that, of 816 samples tested by both methods, the titres of 807 (98-9 %) sera were in close agreement within an acceptable twofold difference. Trypsin-treated human group 0 erythrocytes usually provided titres that were twofold higher than those obtained with chick erythrocytes. In general, a very good correlation between the two methods was obtained. Data are presented that emphasise the importance of trypsin treatment of human group 0 erythrocytes before use in the HAI method. Furthermore, we found that trypsin-treated human group 0 erythrocytes can be stored for periods of up to 30 days and used in the HAI test without any appreciable loss of sensitivity or specificity. Moreover, we replaced chick erythrocytes with trypsintreated human group 0 erythrocytes in the sucrose density gradient/HAl method used for the detection of rubella virus-specific IgM and found it to be a very satisfactory method. In view of these findings we recommend that trypsin-treated human group 0 erythrocytes should replace chick erythrocytes in the standard rubella HAl test since the former provided not only a more sensitive, more economic, and less time-consuming method but also a technique which is as specific as that using chick erythrocytes.The rubella haemagglutination-inhibition (HAI) test using day-old chick erythrocytes is the most widely used technique for both diagnostic and epidemiological studies on rubella. However, in most developing countries, such as Kuwait, a continuous supply of day-old chick cells from a commercial source is not usually available, and the use of this technique for such purposes is therefore limited.Quirin et al. (1972) andIwakata et al. (1974) provided preliminary data, which suggested that day-old chick erythrocytes could effectively be replaced by trypsin-treated human group 0 erythrocytes in the HAI method without affecting the sensitivity or specificity of the test. This encouraged us to investigate this possibility further, and in this paper we report our results. Furthermore, we have extended our investigation to show that trypsin-