Oral Presentation Society of Obstetric Medicine of Australia and New Zealand and Australasian Diabetes in Pregnancy Society Joint Scientific Meeting 2017

A NOVEL CALCULATOR TO DETERMINE THE RISK OF INSULIN THERAPY IN WOMEN WITH GDM (#41)

Tang Wong 1 2 3 , Robyn Barnes 1 4 , Glynis P Ross 1 2 , N Wah Cheung 2 5 , Jeff R Flack 1 3 6
  1. Department of Diabetes and Endocrinology, Bankstown-Lidcombe Hospital, Sydney, NSW, Australia
  2. University of Sydney, Sydney, Australia
  3. University of NSW, Sydney, NSW, Australia
  4. University of Newcastle, Newcastle, NSW, Australia
  5. Department of Diabetes & Endocrinology, Westmead Hospital, Westmead, NSW, Australia
  6. Western Sydney Univerisity, Sydney, NSW, Australia

Background: We previously published a 7-point risk factor predictor model for insulin therapy in women with gestational diabetes (GDM)1.

Aim: To create a risk calculator for insulin therapy weighted according to the coefficients of variables, derived from the 7-point predictor model.

Methods: We analysed de-identified prospectively collected singleton pregnancy data (1992-2014) from women diagnosed with GDM at Bankstown-Lidcombe Hospital according to ADIPS(1998) criteria2. A logistic regression model was run with the seven dichotomised significant independent predictors of insulin therapy: maternal age >30 years, family history of diabetes, pre-pregnancy obesity (BMI ≥30 kg/m2), prior GDM, early diagnosis of GDM (<24 weeks gestation), fasting venous blood glucose level (≥5.3 mmol/l) and HbA1c at GDM diagnosis ≥5.5% (≥37 mmol/mol) on oGTT. A weighted risk score (WRS) using coefficients derived from the model was defined as:

WRS = constant + coefficient1 x variable1+......+coefficient7 x variables7.

Probability of insulin requirement was = eWRS/(1+eWRS).

Results: There were a total 3075 GDM pregnancies. The logistic regression model demonstrated that diagnosis <24 weeks gestation and fasting plasma glucose ≥5.3 mmol/L were the strongest predictors of insulin requirement. The weakest predictor of insulin requirement was age>30. An electronic risk calculator (Microsot Excel 2007) was developed to calculate the probability of insulin therapy using the coefficients and formula described above (example patient shown below)

598afd8685cc4-Insulin+risk+calculator.jpg

Receiver operated characteristic (ROC) curves were plotted for both the unweighted 7-point scoring system versus the weighted risk/probability scores. The AUC were 0.715 (95% CI 0.693 - 0.736, p <0.0001) vs 0.730 (95% CI 0.710 - 0.751, p<0.0001) respectively.

Conclusion: A weighted risk/probability score calculator performed better than an unweighted 7 point system in predicting the likelihood of insulin therapy in women with GDM. This is a practical tool which can be used to identify GDM patients for closer monitoring or early insulin treatment

 

  1. (1) Barnes R, Wong T, Ross G, Jalaludin, B, Wong V, Smart C, Collins C, MacDonald-Wicks L, Flack JR Diabetologia, 2016, Vol.59(11), pp.2331-2338
  2. (2) Hoffman L, Nolan, C, Wilson, JD, Oats JJN, Simmons D (1998) Gestational diabetes mellitus management guidelines. The Australasian Diabetes In Pregnancy Society. MJA pp169:93-97.