Does the International Classification of Disease (ICD-9) code accurately identify neonates who clinically have hypoxic-ischemic encephalopathy?

Abstract

Background/aims: Hypoxic-ischemic encephalopathy (HIE) refers to neonatal neurological signs and symptoms of hypoxia and/or ischemia. Our aim was to determine the accuracy of ICD-9 codes to identify newborns with HIE confirmed by umbilical cord blood analysis.

Methods: ICD-9 codes in the newborn chart for birth trauma, birth asphyxia, intrauterine hypoxia, and fetal distress were used to identify newborns with suspected HIE by neonatal personnel. Maternal charts were reviewed for umbilical cord gases meeting the HIE clinical criteria.

Results: There were 21,008 deliveries at center I and 17,540 at center II. ICD-9 codes identified 172 neonates, 49 infants (2.3‰ births) at center I and 123 neonates (7‰) at center II. Only 3 neonates (6%) were ≥34 weeks and none met ACOG criteria [umbilical artery pH <7.00 or base excess (BE) ≥12 mmol/l at center I]. At center II, 80 infants were ≥34 weeks but only 5/123 (4%) met the ACOG clinical criteria for HIE (pH <7.00, BE ≥12 mmol/l, and Apgar ≤3 at 5 min).

Conclusions: ICD-9 codes are unreliable in identifying birth asphyxia and cannot identify newborns meeting the clinical criteria for intrapartum HIE.