Creatine-kinase (CK) and pyruvate-kinase (PK) activities in cord blood of normal newborn infants: Application to duchenne muscular dystrophy screening programs

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Abstract
Creatine-kinase (CK) and pyruvate-kinase (PK) were determined in cord blood samples from 125 normal newborn infants in order 1) to investigate the correlation between CK and PK, 2) to evaluate a possible influence of the mode of delivery (cesarean section versus vaginal delivery) and birth weight on enzyme activity, 3) to establish normal values for both sexes. In the present investigation, the enzyme activities of cord blood were significantly higher than in the normal adult, and no correlation was observed between enzyme activity and mode of delivery or birthweight. Although there was an apparent and significant correlation (r = 0.5) between CK and PK levels in cord blood samples, in no case did we find both high CK and PK values, something that would suggest preclinical DMD or a false-positive result. These results have led us to suggest determination of serum PK activity in male newborn screening programs. This would allow an early discrimination between false-positives and preclinical cases already in the neonatal period. Furthermore, the concomitant use of PK and CK in boys not walking by 18 months could be a useful test for diagnosing preclinical DMD boys.