Revised normal ranges for six serum enzymes: Further statistical analysis and the effects of different treatments of blood specimens

Abstract

Blood specimens from healthy adults of both sexes were each divided in four portions for immediate assay, after 24 h chilling while clotting, and after 24 h at 25° both clotted and heparinised. Each serum or plasma was assayed for six clinically important enzymes, and for sodium and potassium. The normal ranges, derived from the portions assayed immediately, were examined for the effects of sex, age, Rh and ABO blood groups, and time of day at venepuncture. Assay on different days obscured the normal female diurnal cycle, important in diagnosis. Enzyme values in females seemed inversely related to ovarian oestrogens, which could account for sex differences in values. Clotting 24 h at 25° caused least change, allowing overnight mailing, and heparinising little more ; but chilling 24 h caused an erythrocyte efflux of potassium generally and of enzymes individually, both without the least haemolysis. Potassium efflux was immediate and steady, but reversible on warming if glucose remained. The changes causing enzyme efflux were irreversible, established within an hour and maximal around 9 hours, with efflux itself latent for some 6 hours then self-limiting, as if from an erythrocyte fraction. This effect on enzymes was rapid and complete in heparinised blood, but slower and more extensive in clotted blood; the effect on potassium was the same in both. Blood groups played no part. Specimens from children with X-linked (Duchenne) muscular dystrophy (DMD) behaved similarly. The practical implications of these findings in the handling of blood specimens are discussed.