[Alanine aminotransferase (ALAT, GPT): a reevaluation of exclusion limits for blood donors].

Abstract

Background: The screening policy of alanine aminotransferase (ALT) testing in blood donors was reassessed. The cutoff value for ALT levels according to German guidelines has always been controversial. In this study the activity and distribution of ALT in a blood donor population were reevaluated and new exclusion levels were defined.

Methods: 5,706 blood donors were tested for ALT activities with the Reflotron system at 37 degrees C. Donors with ALT levels > 51 IU/l were deferred, a detailed physical examination and additional serologic and biochemical testing were done.

Results: ALT values of blood donors were transformed in logarithmic values in order to get a Gaussian distribution. The mean transformed value +/- SD was calculated with 1.24 +/- 0.14 for females and with 1.35 +/- 0.16 for males, corresponding to mean values of ALT activity of 17.6 and 22.5 IU/l, respectively. Exclusion levels of > 33.4 IU/l for female and > 46.7 IU/l for male blood donors (geometric mean +2.0 SD) predict a loss of donations of 2.8 and 2.7%, respectively, cutoff values of > 39.1 or > 56.1 IU/l (geometric mean +2.5 SD) a loss of 1.8 and 1.4%, respectively. The most likely causes of elevated ALT levels in 166 of our donors included daily alcohol use (82), infections with/without antibiotic medication (29), therapy with hepatotoxic drugs (8), strenuous exercises (5), bodybuilding complemented by anabolic steroids (2), acute infections with HCV (1), HBV (1) and CMV (1), alcohol/drug abuse and detection of HCV antibodies (1).

Conclusions: ALT screening is still considered a useful indicator of risk donors despite its nonspecificity and limited predictive value. The selection of the appropriate cutoff value has always been disputed. The present exclusion level of > 45 IU/l (25 degrees C), analogous to > 81.8 IU/l (37 degrees C), does not even take into account such a variable as sex. The cutoff value above 4.5 SD of the geometric mean for females and above 3.5 SD for males seems to be of limited medical and practical value.