title: Accuracy of ICD-9-CM coding to identify small for gestational age newborns.
abstract: OBJECTIVE
  This study aimed to evaluate the accuracy of the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis code for small for gestational age (SGA) recorded in administrative healthcare records using birthweight and gestational age information recorded in electronic medical records.
  
  
  METHODS
  We used billing and medical records from women aged 13-55 years who delivered at a tertiary care center in the USA between 2004 and 2011. Information on birthweight, gestational age at birth, and ICD-9-CM code for SGA, 656.5x, was abstracted from the database. Each infant's birthweight percentile for gestational age was calculated on the basis of published US references; infants below the 10th percentile were classified as SGA. The performance characteristics of SGA ICD-9-CM diagnosis code against SGA classification based on birthweight and gestational age were calculated, for all deliveries and by strata of demographic and delivery characteristics.
  
  
  RESULTS
  We identified 51 292 singleton live birth deliveries. The prevalence of SGA infants calculated from birthweight and gestational age at birth was higher (13%) than the prevalence based on ICD-9-CM code (2%). Sensitivity of the SGA ICD-9-CM code was 14.2%, specificity was 99.7%, positive predictive value was 86.8%, and negative predictive value was 88.4%. Stratification by demographic and delivery characteristics yielded similar results.
  
  
  CONCLUSIONS
  Identification of SGA infants using ICD-9-CM code, 656.5x, from administrative healthcare records has low sensitivity but high specificity; the accuracy did not differ across demographic and delivery characteristics. Thus, although this source of information would underestimate the prevalence of SGA, it could produce valid relative risk estimates.
authors: Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA.
authors: Kelesitse
authors: K
authors: Phiri
authors: Sonia
authors: S
authors: Hernandez-Diaz
authors: Lawrence C
authors: LC
authors: Tsen
authors: Karen M
authors: KM
authors: Puopolo
authors: John D
authors: JD
authors: Seeger
authors: Brian T
authors: BT
authors: Bateman
mesh_terms: D000293:Adolescent; D000328:Adult; D001724:Birth Weight; D016208:Databases, Factual; D003944:Diagnostic Techniques, Obstetrical and Gynecological / Q000592:standards*; D005260:Female; D049674:History, 21st Century; D006801:Humans; D007236:Infant, Small for Gestational Age; D038801:International Classification of Diseases / Q000592:standards*; D008875:Middle Aged
keywords: ICD-9-CM codes; gestational age; healthcare records; pharmacoepidemiology; sensitivity; small for gestational age; specificity
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