Validity of hospital discharge records to identify pregestational diabetes in an Italian population

Lucia Borsari, Carlotta Malagoli, Federica Violi, Marco Vinceti, Paola Ballotari, Rossella Rodolfi, Fausto Nicolini, Paola Ballotari, Gianfranco De Girolamo, Karin Bonora, Oreste Capelli

Research output: Contribution to journalArticlepeer-review


Aims 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.

Original languageEnglish
Pages (from-to)106-111
Number of pages6
JournalDiabetes Research and Clinical Practice
Publication statusPublished - Jan 1 2017
Externally publishedYes


  • Pregestational diabetes
  • Pregnancy
  • Registers
  • Routinely collected data

ASJC Scopus subject areas

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism
  • Endocrinology

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