Application of parallel line bioassay method to the potency test of anti-HBs immunoglobulin

The parallel line bioassay method was applied to the potency test of anti-HBs immunoglobulin by radioimmunoassay (RIA) in an attempt to express the relative potency of three test samples in terms of ratio to the BoB reference preparation. By plotting the net c.p.m. readings without being divided by the 'cut-off' values against the dilution factors, both being converted to log10, parallelism between linear regression lines could be observed within wide ranges. Calibration of relative potency was possible wherever the regression lines were parallel, thus making any attempt of comparison at specified points alone, such as ED50, unnecessary.