Normal values of creatine kinase and of MB-creatine kinase at birth in healthy babies.

BACKGROUND: Today, few studies have been accomplished in order to determine serum creatine kinase (CK) activity in newborns by considering small groups of babies and without taking into account gestational age (GA) differences. Some authors have demonstrated that neonatal CK activity value at birth is higher than the normal range of CK activity considering for adults or older children. The objective of this study is to assess normal values of CK and MB-CK in neonatal blood, according to babies' GA.

METHODS: We retrieved the clinical files of 140 babies admitted into Siena Hospital NICU in a 2-years period, when CK was assessed routinely to all babies at birth. We selected files from 114 newborns and we divided the cohort into group A (non-stressed; n=41) and group B (stressed; n=73) on the basis of Apgar score and signs of neurological lesions. We compared CK and MB-CK values in the two groups according to GA.

RESULTS: Mean CK value of the 41 non-stressed babies' samples: 413 IU/L (232 SD). CK significantly increases with GA. No differences are present in total CK activity between stressed vs non-stressed babies; but a significant difference appears in these two groups for MB-CK (mean values: 456 vs 175 IU/L).

CONCLUSIONS: This is the first study that compares CK and MB-CK values at birth according to the GA of the babies. CK values increase with GA, and stressed babies have higher MB-CK values than the non-stressed babies. These reference values are important for clinical practice.