Serum creatine phosphokinase in normal newborns

283. Serum creatine phosphokinase in normal newborns. Serum creatine phosphokinase (CPK) activity in 70 normal newborns was found to be significantly higher than the normal values found in adults or older children, and in some cases reached a level up to 10 times normal. It declined to near normal activity during the first 4 days and to normal level of activity by age 6-10 weeks. No clear correlation between birth trauma and increase in serum CPK activity was shown. CPK activity in cord blood was lower than in venous and capillary blood. Because of the increased CPK activity found in normal newborns, screening for Duchenne-type muscular dystrophy should be postponed for a few weeks after delivery. Scarcity of data on serum creatine phospho-kinase (CPK) activity in normal newborns, the different laboratory methods used in previously published studies, and the possibility of using the serum CPK activity in newborn screening for Duchenne muscular dystrophy (Zellweger and Antonik, 1975) prompted this study of CPK activity in 70 normal newborns. Materials and methods Blood was obtained from 70 normal newborns selected at random, at ages varying from 10 minutes to 10 weeks. The blood was obtained from three sources (1) umbilical cord blood immediately after severing of the cord; (2) venous blood obtained from antecubital fossa or dorsum of a hand; and (3) capillary blood ob-tained by heelprick. All blood samples, except for a few obtained from the umbilical cord, were examined within 12 hours. Muscle trauma during blood drawing was avoided as far as possible. Serial capillary blood samples were obtained from 27 babies. Capillary and venous blood were obtained simultaneously from 17 babies, and cord and capillary blood were obtained simultaneously from 24 newborns. The CPK activity in babies delivered vaginally, by elective caesarean sec-tion (CS) and by emergency CS, was compared. CPK was assayed at 30°C according to the method of Rosalki (1967), with a centrifugal analyser (Centrifi-Chem) and Boehringer Mannheim reagent kits (U