[alpha 1-antitrypsin: reference values in serum and plasma with benzoyl-D,L-arginine-p-nitroanilide, a chromogenic...

Reference values for alpha 1-antitrypsin were determined using a commercially available kit for continuous assay at 25 degrees C. With a population of 100 probands aged between 20 and 60 years, a reference range of 1.4-2.4 kIU/l (1.9-3.4 g/l) was obtained for serum, and 1.4-2.1 kIU/l (1.9-3.0 g/l) for plasma. In each case, these ranges correspond to the 5th to 95th percentile. No variations according to age or sex were observed, or was any difference noted between preprandial and postprandial activities, or between values in smokers and nonsmokers. Significantly different values were found in the group of women taking oral steroid contraceptives and the group not taking such contraceptives. If the dilution of the blood sample with citrate solution is taken into account in calculating the activity in citrated plasma, it is apparent that higher values are found in plasma than in serum (median 13%): Hence, the in vivo-alpha 1-antitrypsin activity can most probably be better determined using a plasma sample.