title: Validity of hospital discharge records to identify pregestational diabetes in an Italian population.
abstract: OBJECTIVE
  In recent years, the prevalence of pregestational diabetes (PGDM) and the concern about the possibility of adverse pregnancy outcomes in affected women have been increasing. Routinely collected health data represent a timely and cost-efficient approach in PGDM epidemiological research. This study aims to evaluate the reliability of hospital discharge (HD) coding to identify a population-based cohort of pregnant women with PGDM and to assess trends in prevalence in two provinces of Northern Italy.
  
  
  METHODS
  We selected all deliveries occurred in the period 1997-2010 with ICD-9-CM codes for PGDM in HD record and we matched up to 5 controls from mothers without diabetes. We used Diabetes Registers (DRs) as the gold standard for validation analysis.
  
  
  RESULTS
  We selected 3800 women, 653 with diabetes and 3147 without diabetes. The agreement between HD records and DRs was 90.7%, with K=0.58. We detected 350 false positives and only 1 false negative. Sensitivity was 99.3%, specificity 90.0%, positive predictive value 46.4% and negative predictive value 99.9%. Of the false positives, 48.6% had gestational diabetes and 2.3% impaired glucose tolerance. After the validation process, PGDM prevalence decreased from 4.4 to 2.0 per 1000 deliveries.
  
  
  CONCLUSIONS
  Our results show that HD facilitate detection of almost all PGDM cases, but they also include a large number of false positives, mainly due to gestational diabetes. This misclassification causes a large overestimation of PGMD prevalence. Our findings require accuracy evaluation of ICD-9-CM codes, before they can be widely applied to epidemiological research and public health surveillance related to PGDM.
authors.affiliation: Sezione di Sanità Pubblica, Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Università di Modena e Reggio Emilia, Modena, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Borsari
authors.affiliation: Sezione di Sanità Pubblica, Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Università di Modena e Reggio Emilia, Modena, Italy.
authors.forename: Carlotta
authors.initials: C
authors.lastname: Malagoli
authors.affiliation: Azienda Unità Sanitaria Locale di Reggio Emilia, Reggio Emilia, Italy; Arcispedale Santa Maria Nuova - IRCCS, Reggio Emilia, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Ballotari
authors.affiliation: Azienda Unità Sanitaria Locale di Modena, Modena, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: De Girolamo
authors.affiliation: Azienda Unità Sanitaria Locale di Modena, Modena, Italy.
authors.forename: Karin
authors.initials: K
authors.lastname: Bonora
authors.affiliation: Sezione di Sanità Pubblica, Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Università di Modena e Reggio Emilia, Modena, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Violi
authors.affiliation: Azienda Unità Sanitaria Locale di Modena, Modena, Italy.
authors.forename: Oreste
authors.initials: O
authors.lastname: Capelli
authors.affiliation: Azienda Unità Sanitaria Locale di Reggio Emilia, Reggio Emilia, Italy.
authors.forename: Rossella
authors.initials: R
authors.lastname: Rodolfi
authors.affiliation: Azienda Unità Sanitaria Locale di Reggio Emilia, Reggio Emilia, Italy.
authors.forename: Fausto
authors.initials: F
authors.lastname: Nicolini
authors.affiliation: Sezione di Sanità Pubblica, Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Università di Modena e Reggio Emilia, Modena, Italy. Electronic address: marco.vinceti@unimore.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Vinceti
mesh_terms: D000328:Adult; D016640:Diabetes, Gestational / Q000453:epidemiology*; D005260:Female; D006753:Hospital Records; D006801:Humans; D007558:Italy; D063886:Patient Discharge Summaries; D011247:Pregnancy; D015203:Reproducibility of Results
keywords: Pregestational diabetes; Pregnancy; Registers; Routinely collected data