Poster Presentation Australasian Diabetes in Pregnancy Society Annual Scientific Meeting 2016

Poor coding and reporting of GDM in administrative data grossly underestimates the impact on health services. (#133)

Jeff R Flack 1 2 3 , Tang Wong 1 2 , Gamal Matthias 4 , Glynis P Ross 1 5
  1. Diabetes Centre, Bankstown-Lidcombe Hospital, Bankstown, NSW, Australia
  2. Faculty of Medicine, University of NSW, Sydney, NSW, Australia
  3. School of Medicine, University of Western Sydney, Sydney, NSW, Australia
  4. Department of Obstetrics & Gynaecology, Bankstown-Lidcombe Hospital, Bankstown, NSW, Australia
  5. Faculty of Medicine, University of Sydney, Sydney, NSW, Australia

Background The administrative ‘Perinatal Data Collection’ (PDC) dataset is collected by all state-wide Obstetric Services and data are collated and reported annually by the Ministry of Health as the ‘NSW Mothers and Babies Report’. From 2008 to 2014, gestational diabetes (GDM) had a reported rate of 4.8% increasing to 7.5%. Many clinicians believe this rate is significantly under reported, with several reports supporting this (1-3).

Aim To assess and validate the rates of GDM and pre-gestational diabetes as reported in the PDC from our hospital over a 5 year period.

Methods We reviewed 5 years of PDC data for Bankstown-Lidcombe Hospital for the years 2011-2015, and compared this with data prospectively collected in our GDM/diabetes database as part of routine care. Data were matched by MRN thence records known to have been managed by our Department with GDM and pre-gestational diabetes were reviewed in regards to the ultimate PDC coding that had been made.

Results There were a total 11,182 deliveries. The PDC data extract reported a total of 354 with pre-gestational diabetes (3.2% of births), and 348 with GDM (3.1% of births). From our database, respective numbers were 65 (0.6%) and 1576 (14.1%). Firstly, this represents an underreporting overall of 57.2%. Secondly, much of the miscoding of GDM as diabetes was predominantly in the last 3 years. Only 53.2% of these miscoded individuals (coding GDM as pre-gestational diabetes) were managed with insulin, the remainder were GDM women managed on diet alone.

Conclusions These data confirm our suspicion that GDM was under reported, whilst pre-gestational diabetes was significantly over reported. We were surprised by the significant degree of miscoding which requires investigation and correction. Appropriate allocation of resources to manage the increasing prevalence of GDM will not occur without appropriate data reporting. Urgent action is needed to improve this situation.

  1. Zheng ASY, Morris G, Moses RG. The prevalence of gestational diabetes mellitus: The accuracy of the NSW perinatal data collection based on a private hospital experience. Aust N Z J Obstet Gynaecol 2016; DOI: 10.1111/ajo.12438
  2. Moses RG, Webb AJ, Comber CD. Gestational diabetes mellitus: accuracy of Midwives Data Collection. Med J Aust 2003; 179: 218–219.
  3. Moses RG, Colagiuri S. The extent of undiagnosed gestational diabetes mellitus in New South Wales. Med J Aust 1997; 167 (1): 14–16.