On the Significance of Blood Sampling Time in Neonatal Neurologic Prognosis Using Creatine Kinase BB

ABSTRACT

PURPOSE: To investigate the cut-off value of creatine kinase (CK) BB according to blood sampling time in predicting neonatal prognosis, we studied the time-related releasing pattern of CK isoenzymes after birth asphyxia. METHODS: CK was measured within 1 hour and at 6-10 hours after birth from 45 newborn infants who were suspected to be perinatal asphyxia or fetal distress. The infants were followed up for 1 year to evaluate neonatal prognosis. RESULTS: Total CK, CK-MM, CK-BB and CK-BB% from blood samples within 1 hour after birth were 758.6U/L, 588.7U/L, 105.7U/L and 17.5%, respectively, and those at 6-10 hours after birth were 1,298.0U/L, 1,127.1U/L, 57.7U/L and 6.6%, respectively. When the cut-off value of CK-BB measured within 1 hour after birth was set to 200U/L, positive predictive value (PP) was 0.38 and negative predictive value (NP) was 0.76 for infants who died within 28 days. For neurologic sequelae on 1-year-old PP and NP are 0.33 and 0.76 respectively, for neonatal seizures, 0.38 and 0.92, for abnormal brain sonogram cases 1.0 and 0.88, repectively. CONCLUSION: CK-BB and CK-BB% were measured significantly higher within 1 hour after birth than at 6-10 hours after birth. Because of different CK-BB levels between 2 separate sampling times, we have to use 2 different cut-off values. It is recommended that cut-off values for CK-BB and CK-BB%, measured within 1 hour after birth, are 200U/L and 20%, respectively and cut-off values for CK-BB and CK-BB% measured in 6-10 hours after birth are 100U/L and 10%, respectively.