The DIAMIND study: postpartum SMS reminders to women who have had gestational diabetes mellitus to test for type 2 diabetes: a randomised controlled trial - study protocol

BACKGROUND Postpartum follow up of women who have been found to have gestational diabetes during pregnancy is essential because of the strong association of gestational diabetes with subsequent type 2 diabetes. Postal reminders have been shown to increase significantly attendance for oral glucose tolerance testing postpartum. It is possible that a short message service (text) reminder system may also be effective. This trial aims to assess whether a text message reminder system for women who have experienced gestational diabetes in their index pregnancy will increase attendance for oral glucose tolerance testing within six months after birth. METHODS/DESIGN Design: Single centre (Women’s and Children’s Hospital, South Australia), parallel group randomised controlled trial. Inclusion criteria: Women diagnosed with gestational diabetes in their index pregnancy (oral glucose tolerance test with fasting glucose ≥ 5.5 mmol/L and/or two hour glucose ≥ 7.8 mmol/L), with access to a mobile phone, whose capillary blood glucose profile measurements prior to postnatal discharge are all normal (fasting glucose < 6.0 mmol/L, postprandial glucoses < 8.0 mmol/L). Exclusion criteria: Pregestational diabetes mellitus, triplet/higher order multiple birth or stillbirth in the index pregnancy, requirement for interpreter. Trial entry and randomisation: Allocation to intervention will be undertaken using a telephone randomisation service (computer-generated random number sequence generation, with balanced variable blocks, and stratification by insulin requirement). Study groups: Women in the intervention group will receive a text reminder to attend for an oral glucose tolerance test at 6 weeks postpartum, with further reminders at 3 months and 6 months if they do not respond to indicate test completion. Women in the control group will receive a single text message reminder at 6 months postpartum. Blinding: Baseline data collection will be undertaken blinded. Blinding of participants and blinded collection of primary outcome data will not be possible for this study. Primary study outcome: Attendance for the oral glucose tolerance test within 6 months postpartum. Sample size: 276 subjects will be required to show an 18% absolute increase in the rate of attendance (α=0.05 two tailed, β=80%, 5% loss to follow up) from 37% to 55% in the intervention group. DISCUSSION Given the heightened risk of impaired glucose tolerance and type 2 diabetes in women who have had gestational diabetes, ensuring the highest possible rate of attendance for postpartum glucose tolerance testing, so that early diagnosis and intervention can occur, is important. A text message reminder system may prove to be an effective method for achieving improved attendance for such testing. This randomised controlled trial will assess whether such a system will increase rates of attendance for postpartum oral glucose tolerance testing in women who have experienced gestational diabetes. TRIAL REGISTRATION Australian New Zealand Clinical Trials Registry - ACTRN12612000621819Emer Heatley, Philippa Middleton, William Hague and Caroline Crowthe