Surrogate testing for non-A, non-B hepatitis in Queensland, Australia: an ALT microtitre tray method for screening blood donors.

The estimation of plasma alanine aminotransferase (ALT) has been proposed as a surrogate test to identify potential non-A, non-B hepatitis carriers in blood donor populations. This report describes an ALT screening procedure which uses wells of microtitration trays as reactant vessels. The method utilizes a rate reading photometer, is economical and conveniently fits into the routine workflow. Within-batch and between-batch precision was 4.1% and 6.3% at enzyme concentrations of 49 IU/I. Results of testing 29,675 healthy blood donors gave values which ranged between 1.0 IU/I and 214 IU/I. A study of 762 donations showed a significant difference in mean ALT values between males and females (p less than 0.01). When a cut-off value of 46 IU/I was used, 2.5 percent of donations were considered unsuitable for transfusion. The medico-legal implications that may arise from the introduction of this screening test into the routine work flow are discussed.