An International Standard for specifying the minimum potency of anti-D blood-grouping reagents: evaluation of a candidate preparation in an international collaborative study.
OBJECTIVE
The aim of this study was to evaluate a lyophilized monoclonal immunoglobulin M (IgM) anti-D preparation for use as an International Standard to specify a recommended minimum acceptable potency of anti-D blood-grouping reagents.


METHODS
The candidate International Standard (99/836) for specifying the minimum potency of anti-D blood-grouping reagents was evaluated against a wide range of commercial anti-D blood-grouping reagents in an international collaborative study involving 20 laboratories in 13 countries. Laboratories titrated reconstituted 99/836, in parallel with as many commercial anti-D blood-grouping reagents as were available to them, in tube tests according to specified haemagglutination methodology for low-protein (e.g. monoclonal IgM) and high-protein (e.g. polyclonal) reagents. The ratios of the mean end-point titres of the reagents to that of 99/836 within each laboratory were calculated.


RESULTS
The ratios of the mean titres of the low-protein reagents to the mean titre of 99/836 within a laboratory fell between 0.25 and 2 for 43 of the 45 low-protein anti-D reagents tested (i.e. the potencies of the low-protein reagents compared with 99/836 were between a 1:4 dilution of 99/836 to twice as potent as 99/836). The ratios of the mean titres of the high-protein reagents to the mean titre of 99/836 within a laboratory fell within 0.125 and 1 for eight out of the 10 high protein reagents tested.


CONCLUSIONS
By international consensus, a 1:3 dilution of reconstituted 99/836 was deemed appropriate to define a recommended minimum acceptable potency of low-protein anti-D blood-grouping reagents. A 1:8 dilution of reconstituted 99/836 was deemed appropriate to define a recommended minimum acceptable potency of high-protein anti-D blood-grouping reagents. On the basis of the results presented here, 99/836 was established by the World Health Organization as the 1st International Standard for specifying the minimum potency of anti-D blood-grouping reagents, in tube tests.
Thorpe
S J
SJ
National Institute for Biological Standards and Control, Potters Bar, Herts., 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
D000911:Antibodies, Monoclonal; D001788:Blood Grouping and Crossmatching / Q000379:methods / Q000592:standards*; D006386:Hemagglutination Tests / Q000379:methods / Q000592:standards; D006801:Humans; D007075:Immunoglobulin M; D007202:Indicators and Reagents / Q000592:standards; D007391:International Cooperation; D012015:Reference Standards; D012204:Rh-Hr Blood-Group System / Q000276:immunology*
D000911:Antibodies, Monoclonal; D007075:Immunoglobulin M; D007202:Indicators and Reagents; D012204:Rh-Hr Blood-Group System; C026410:Rho(D) antigen