Predicting type 2 diabetes mellitus using haemoglobin A1c: A community-based historic cohort study

Abstract

Background: The ADA 2010 guidelines added HbA1c ≥ 6.5% as a criterion for diagnosing diabetes mellitus type 2.

Objective: To evaluate the HbA1c test in predicting type 2 diabetes in a high risk population.

Methods: A community-based historic cohort study was conducted including 10 201 patients, who had not been diagnosed with diabetes, and who underwent HbA1c test during the years 2002–2005. Data was retrieved on diabetes risk factors and the onset of diabetes (according to the ADA 2003 criteria), during a follow-up period of five-to-eight years.

Results: Mean age was 58.25 ± 15.58 years; mean HbA1c level was 5.59 ± 0.55% and 76.8% had a BMI > 25 kg/m² (mean: 30.74 ± 8.30). In a Cox proportional hazards regression model, the risk of developing type 2 diabetes was 2.49 (95% CI: 1.29–3.71) for 5.5% ≤ HbA1c < 6% at baseline, 4.82 (95% CI: 2.83–8.20) for 6% ≤ HbA1c < 6.5% at baseline and 7.57 (95% CI: 4.43–12.93) for 6.5% ≤ HbA1c < 7% at baseline, compared to HbA1c < 4.5%. The risk of developing diabetes was 1.14 (95% CI: 1.05–1.25) for male gender, 1.16 (95% CI: 1.04–1.28) for cardiovascular diseases and 2.06 (95% CI: 1.80–2.35) for overweight (BMI > 25 kg/m²) at baseline. Neither age nor low socio-economic status was associated with increased risk of diabetes.

Conclusion: Levels of HbA1c ≥ 5.5% were associated with increased risk of type 2 diabetes during a five-to-eight-year follow-up period. Findings support the use of HbA1c testing as a screening tool in populations at risk of developing diabetes.

Keywords::

• diabetes
• family medicine
• haemoglobin A1c
• overweight

ACKNOWLEDGEMENTS

This study was performed as part of fulfilment of the M.D. thesis requirements of Nataly Lerner at the Sackler Faculty of Medicine, Tel-Aviv University.

The study was presented in the annual 28th conference of the Israel Diabetes Association, on 14 May 2011, Air-Port City, Israel, and in the annual Israel Family Physicians Organization Conference, on 27 March 2012, Jerusalem, Israel.

Declaration of interest: No relevant conflicts of interest or financial disclosures to report. The authors alone are responsible for the content and writing of the paper.