Comparison between creatine kinase brain isoenzyme (CKBB) activity and Sarnat score for prediction of adverse outcome following perinatal asphyxia

AIM: To assess whether plasma creatine kinase brain isoenzyme (CKBB) levels or Sarnat scores are more accurate for prediction of poor neurological outcome in babies with suspected birth asphyxia. METHODS: In a retrospective study of 97 babies CKBB levels were compared to the presence of severe hypoxic ischaemic encephalopathy (HIE) as a predictive test for these outcomes: developmental delay, cerebral palsy, visual problems, deafness or death from perinatal asphyxia. The tests were compared using positive predictive values (PPV) and likelihood ratios (LR) with confidence intervals (CI). RESULTS: 3 babies had died from perinatal asphyxia and 14 survivors were found to have neurological or developmental problems. CKBB was elevated in babies with severe HIE (p = 0.0004). A receiver operator characteristic (ROC) curve showed the optimal discriminating value for CKBB to be 21 IU/L but the CKBB was a poor predictive test. For prediction of adverse outcome: CKBB > 21 sensitivity 76%, specificity 40%, PPV 21% and LR 1.3 (95% CI 0.8-1.7). Severe HIE sensitivity 53%, specificity 95%, PPV 69% and LR 10.6 (95% CI 3.8-29.2). CONCLUSION: CKBB is elevated following birth asphyxia but is a poor predictor of adverse neurological outcome.