Assessing the Burden of Neonatal Abstinence Syndrome: Validation of ICD-9-CM Data, Florida, 2010-2011

On October 1, 2015, the United States transitioned from using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) to ICD-10-CM. Continuing to monitor the burden of neonatal abstinence syndrome (NAS) after the transition presently requires use of data dependent on ICD-9-CM coding to enable trend analyses. Little has been published on the validation of using ICD-9-CM codes to identify NAS cases.

To assess the validity of hospital discharge data (HDD) from selected Florida hospitals for passive NAS surveillance, based on ICD-9-CM codes, which are used to quantify baseline prevalence of NAS.

We reviewed infant and maternal data for all births at 3 Florida hospitals from 2010 to 2011. Potential NAS cases included infants with ICD-9-CM discharge codes 779.5 and/or 760.72 in linked administrative data (ie, HDD linked to vital records) or in unlinked HDD and infants identified through review of neonatal intensive care unit admission logs or inpatient pharmacy records. Confirmed infant cases met 3 clinician-proposed criteria. Sensitivity and positive predictive value were calculated to assess validity for the 2 ICD-9-CM codes, individually and combined.

Of 157 confirmed cases, 134 with 779.5 and/or 760.72 codes were captured in linked HDD (sensitivity = 85.4%) and 151 in unlinked HDD (sensitivity = 96.2%). Positive predictive value was 74.9% for linked HDD and 75.5% for unlinked HDD. For either HDD types, the single 779.5 code had the highest positive predictive value (86%), lowest number of false positives, and good to excellent sensitivity.

Passive surveillance using ICD-9-CM code 779.5 in either linked or unlinked HDD identified NAS cases with reasonable validity. Our work supports the use of ICD-9-CM code 779.5 to assess the baseline prevalence of NAS through 2015.