International standards for minimum potency of anti-A and anti-B blood grouping reagents: evaluation of candidate preparations in an international collaborative study.
OBJECTIVE
The aim of the study was to evaluate lyophilized monoclonal IgM anti-A and anti-B preparations for use as international standards (IS) to specify recommended minimum potencies of anti-A and anti-B blood grouping reagents in tube tests.


METHODS
The candidate IS for minimum potency of anti-A and anti-B blood grouping reagents, codes 03/188 and 03/164, respectively, were evaluated against a wide range of commercial anti-A and anti-B blood grouping reagents in an international collaborative study involving 16 laboratories in nine countries. Laboratories titrated 03/188 and 03/164 in parallel with as many commercial anti-A and anti-B blood grouping reagents, respectively, as were available to them, in tube tests according to specified haemagglutination methodology. Three of these laboratories and a further laboratory also titrated 03/188 and 03/164 in parallel with currently available reference preparations for anti-A and anti-B. The ratios of the mean endpoint titres of the anti-A and anti-B reagents to those of 03/188 and 03/164, respectively, within each laboratory were calculated.


RESULTS
The ratios of the mean titres of the anti-A reagents to the mean titre of 03/188 within a laboratory fell within 0.062 and 4, i.e. the potencies of the anti-A reagents were between a sixteenth to four times as strong as 03/188. The ratios of the mean titres of the anti-B reagents to the mean titre of 03/164 within a laboratory also fell within 0.062 and 4, with one outlier.


CONCLUSIONS
By international consensus, a 1 in 8 dilution of the candidate IS for anti-A, 03/188, and a 1 in 4 dilution of the candidate IS for anti-B, 03/164, were considered appropriate to define the recommended minimum potencies of anti-A and anti-B blood grouping reagents, respectively, in tube tests. On the basis of these results, preparations 03/188 and 03/164 were established by the World Health Organization as International Standards for Minimum Potency of Anti-A and Anti-B Blood Grouping Reagents respectively, and by the US Food and Drug Administration Center for Biologics Evaluation and Research as Minimum Potency Reference Reagents.
Thorpe
S J
SJ
National Institute for Biological Standards and Control, Potters Bar, Hertfordshire, UK. sthorpe@nibsc.ac.uk
Fox
B
B
Heath
A B
AB
Scott
M
M
de Haas
M
M
Kochman
S
S
Padilla
A
A
D000017:ABO Blood-Group System / Q000276:immunology*; D000911:Antibodies, Monoclonal; D001788:Blood Grouping and Crossmatching / Q000592:standards*; D006384:Hemagglutination; D006801:Humans; D007202:Indicators and Reagents / Q000592:standards; D007391:International Cooperation; D012015:Reference Standards; D014481:United States; D014486:United States Food and Drug Administration; D014944:World Health Organization
D000017:ABO Blood-Group System; D000911:Antibodies, Monoclonal; D007202:Indicators and Reagents