Objective: Diagnosing neonatal asphyxia solely according to Apgar score may lead to misdiagnosis. The aim of this study was to explore new and more accurate diagnostic criteria for neonatal asphyxia.
Methods: Totally 10 376 live born neonates in our hospital were consecutively enrolled into the study. The following five items related to birth asphyxia, i.e., antepartum high-risk factors, Apgar scores, umbilical artery blood pH, organ injury, differential diagnosis on the causes of low Apgar score cases were examined and registered. The relationship among the first 4 items were analyzed. By differential diagnosis, the sensitivity and specificity of each index on diagnosing asphyxia and their complementary value on each other were investigated.
Results: The items correlated well with each other (P < 0.01 or < 0.05) but were not entirely parallel and consistent; they could complement but could not substitute for each other. The sensitivity of antepartum high-risk factors, low Apgar scores, umbilical artery blood pH < 7.00 and organ injury was 100%, 100%, 44.44% and 100%, while the specificity was 17.99%, 98.90%, 96.05% and 96.62%, respectively. Of the 230 low Apgar score cases in this series only 50.9% coincided with asphyxia. For the 230 cases, when low Apgar score was combined with umbilical artery blood pH < 7.00, the sensitivity and specificity were 41% and 99.1% and when low Apgar score was combined with umbilical artery blood pH < 7.20, the sensitivity and specificity were 100% and 29.20%, respectively. After organ injury was added, the specificity was increased to 65.49%. When differential diagnosis was further added to exclude the other causes of low Apgar score cases, the misdiagnosis rate was minimized.
Conclusion: Up to now, no single accurate index for diagnosing neonatal asphyxia is available. In order to increase diagnostic bases and reduce misdiagnosis, the criteria of sole Apgar score should be replaced by multi-index diagnostic criteria. Based on the present study, a set of integrated diagnostic criteria for neonatal asphyxia is proposed: (1) prenatal high-risk factors, (2) low Apgar scores (respiratory depression must present), (3) umbilical artery blood pH < 7.00, if only pH < 7.20, the items (2) (4) (5) must be present, (4) hypoxic-ischemic organ injury (at least one organ dysfunction), (5) the other causes of low Apgar scores should be excluded. The last 4 indexes should all be met and the first one serves as reference. If multi-organ (three or more organs) dysfunction and (or) hypoxic-ischemic encephalopathy are present, severe asphyxia can be diagnosed.