Leveraging Existing Birth Defects Surveillance Infrastructure to Build Neonatal Abstinence Syndrome Surveillance Systems - Illinois, New Mexico, and Vermont, 2015-2016

Abstract

Neonatal abstinence syndrome (NAS) is a drug withdrawal syndrome that can occur following prenatal exposure to opioids (1). NAS surveillance in the United States is based largely on diagnosis codes in hospital discharge data, without validation of these codes or case confirmation. During 2004-2014, reported NAS incidence increased from 1.5 to 8.0 per 1,000 U.S. hospital births (2), based on International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis codes identified in hospital discharge data, without case confirmation. However, little is known about how well these codes identify NAS or how the October 1, 2015, transition from ICD-9-CM to the tenth revision of ICD-CM (ICD-10-CM) codes affected estimated NAS incidence. This report describes a pilot project in Illinois, New Mexico, and Vermont to use birth defects surveillance infrastructure to obtain state-level, population-based estimates of NAS incidence among births in 2015 (all three states) and 2016 (Illinois) using hospital discharge records and other sources (varied by state) with case confirmation, and to evaluate the validity of NAS diagnosis codes used by each state. Wide variation in NAS incidence was observed across the three states. In 2015, NAS incidence for Illinois, New Mexico, and Vermont was 3.0, 7.5, and 30.8 per 1,000 births, respectively. Among evaluated diagnosis codes, those with the highest positive predictive values (PPVs) for identifying confirmed cases of NAS, based on a uniform case definition, were drug withdrawal syndrome in a newborn (ICD-9-CM code 779.5; state range = 58.6%-80.2%) and drug withdrawal, infant of dependent mother (ICD-10-CM code P96.1; state range = 58.5%-80.2%). The methods used to assess NAS incidence in this pilot project might help inform other states' NAS surveillance efforts.

FIGURE

Positive predictive value of neonatal abstinence syndrome (NAS) diagnosis codes from the ninth and tenth revisions of International Classification of Diseases, Clinical Modification (ICD-9-CM and ICD-10-CM), by state and infant diagnosis code — Illinois, New Mexico, and Vermont, 2015 * Positive predictive value calculated as follows: [(no. of confirmed NAS)/(no. of confirmed NAS + no. of not confirmed NAS)] x 100. ^† ICD-9-CM diagnosis codes 779.5 and 760.72 were used before October 1, 2015; ICD-10-CM diagnosis codes P96.1 and P04.49 became effective October 1, 2015.