Quantitative determination of antibody against hepatitis B surface antigen: measurement of its binding capacity.

The binding capacity of hepatitis immune globulins (HBIG) and of other anti-HBs containing samples was studied with HBsAg reference samples of defined concentration and subtype. The bound HBsAg was determined by electroimmunodiffusion and expressed as μg of specific protein bound by 1 ml sample. Comparing the results of this method with those of SPRIA, 1 ml of the international HBIG reference preparation, containing 100 arbitrary units, binds 90·6 ± 2·9 μg ml −1 . The detection limit of SPRIA is approximately 1–2 mU ml −1 . Using a standardized SPRIA, it was found that 95% of hepatitis B convalescents and 67% of the positive blood donors have less than 100 mU ml −1 (median value 10 mU ml −1 ). The highly titered group of blood donors (33%) has 0·1 to 35 U ml −1 (median value 0·8 U ml −1 ).