Immune response to HBsAg differently interpreted by RIA and EIA

In the first part of this study anti-HBs developed after vaccination (three different vaccines, sampling at four time intervals after the first injection) or infection (n = 342) was simultaneously tested by Ausab-RIA and Ausab-EIA (Abbot Laboratories). For each vaccination subgroup (vaccine, time) the geometric mean level (GML) of anti-HBs, expressed in IU/l using the Abbott reference panel, was calculated. The ratio GML-RIA/GML-EIA ranged from 1.4 to 2.2. Differences between the vaccine subgroups were found at months 2/3 and month 7, but not at months 12 and 24. The results obtained in convalescent sera by RIA and EIA were similar (ratio GML 1.1). It is concluded that the behaviour of anti-HBs based on the Abbott reference panel differs from that of anti-HBs obtained after vaccination. In the second part of this study, we compared RIA (Abbott Laboratories) with two other EIAs (Organon Teknika): Hepanostika anti-HBs monoclonal (HM) and Hepanostika anti-HBs 'new' (HN). The suitability of these EIAs for detecting anti-HBs greater than 10 IU/l was investigated in sera obtained after vaccination and infection (n = 538). On the first screening, all samples with anti-HBs greater than 10 IU/l (n = 109) in the RIA were detected by HM, whereas 5-7%, dependent on the time of the first incubation step, were negative by HN. The functional sensitivity of HN was 3.9 IU/l (short incubation) or 1.5 IU/l (overnight incubation) and 16.1 IU/l for HM as determined with the Organon reference panel. Sera from three reference panels, as in-house panel, an Abbott panel and an Organon panel were tested in Ausab-RIA, HM and HN. For a serum with the arbitrarily chosen level of 50 IU/l anti-HBs (in-house panel) the results of the in-house panel, the Abbott panel and the Organon panel deviated less by the Ausab-RIA. Since in the Organon-EIAs extreme values of 77 and 35 IU/l were calculated with the Abbott and the Organon panel, respectively, the need for reference sera, the use of which is not related to any particular test system, is stressed once again.