Anti-D Immunoglobulin Preparations: the Stability of Anti-D Concentrations and the Error of the Assay of Anti-D

Abstract

An analysis of the assay of 28 preparations of anti-D immunoglobulin using a radioisotope method carried out at 6-monthly intervals for 2-4.5 years showed an average fall in anti-D concentration ot 10.6% each year, with 99% confidence limits ot 6.8-14.7%. The fall in anti-D concentration after storage at 37°C for 1 month was less than 8%, the minimum change that could be detected. No significant change in physical characteristics of the immunoglobulin were detected. The error of a single estimate of anti-D by the radioisotope method (125I-labelled anti-IgG) used here was calculated to be such that the true value probably (p=0.95) lay between 66 and 150% of the estimated value.

Stability of European Anti-D Immunoglobulin Preparations

“…mean value of loss of activity for the 28-day test at +37°C was slightly lower than the loss after 3-year storage at +4°C (12.3 versus 15.2%), whereas in a British study [1], the loss after 1 month at +37°C was less than 8%, while the average annual fall was 10.6% each year. Such a discrepancy is easily understandable in the light of the discovery which is appar ent in this study that each manufacturer has its own unique preparation concerning the purity of IgG, the stability of IgG in general, and the stability of anti-D-specific antibod ies in particular.…”

“…In a previous study [2], we found that anti-D activity decreased before signs of degradation were apparent on The accelerated degradation test described in the Eu ropean Pharmacopeia is believed to be useful in predicting the stability of anti-D immunoglobulins during their shelf life. This belief is based on anecdotal data from the manu facturers and a few published results [1], The loss of activity for short-term incubation at +37°C is regarded to be pro portional to the loss during the dating period of 3 years at +4°C. The present study supports the above assumption.…”

“…Their anti-D potency according to the manufacturers varied between 178 and 1.374 IU/ml. Anti-D immunoglobulin preparations have been report ed to lose their specific potency before any signs of IgG degradation can be detected [1,2]. In connection with the European Pharmacopoeia requirements for anti-D immu noglobulin preparations, a study was planned to investigate the loss of activity in European preparations during their shelf life in a cold room (+4 ± 2°C) as well as after 28-day storage at +37°C.…”