Serum alanine aminotransferase (ALT) and y-glutamyltransferase (y-GT) activities in north London blood donors

Serum alanine aminotransferase (ALT) and y-glutamyltransferase (y-GT) activities were measured in over 2000 north London blood donors. The results were compared with those from the United States. The percentage of the total donor population with ALT activities above 40 IU/1 in 1986 was greater than that found in our earlier studies in 1973 and 1982 (4*6% compared with 2-8% and 3 1 % , respectively). There was a noticeable difference in the ALT distribution between male and female donors: mean +2-25 SD for male donors was 55*3 IU/1, while that for female donors was 30-8 IU/1 at 37°C. In stability studies the optimal temperature for short term storage (10 days) was 4°C (6-4% loss of activity after 10 days). Surprisingly, storage at lower temperatures ( —35°C and — 80°C) resulted in greater loss of activity.