Clinical features of type 2 diabetes before diagnosis and pathways to the diagnosis: A case–control study

Abstract

To identify and quantify clinical features associated with a future diagnosis of type 2 diabetes, and to record pathways to the diagnosis of diabetes. The risk of type 2 diabetes posed by particular symptoms is largely unknown, especially in unselected populations like primary care. The current mode and setting of diagnosis in the UK are undescribed. This was a population-based case–control study in seven general practices in Bristol, UK. In this study, 105 cases with newly diagnosed diabetes, and 105 age- and sex-matched controls were studied. Their primary care records for two years before diagnosis were examined for symptoms previously reported to be associated with diabetes and for abnormal investigations. Differences between cases and controls were analysed by conditional logistic regression. In cases, the pathways to the diagnosis of diabetes were categorised. In all, 42 (40%) adults with newly diagnosed diabetes were asymptomatic at diagnosis and 84 (80%) were first detected in primary care. Five clinical features were independently associated with diabetes in multivariable analyses. Likelihood ratios for these were: thirst 36 (95% confidence interval 3.0, 440), P = 0.005; weight loss 5.7 (1.3, 26), P = 0.022; skin infections 4.6 (1.7, 12), P = 0.002; fasting glucose >5.6 mmol/L 38 (2.2, 640), P = 0.012; and random glucose >5.6 mmol/L 15 (2.5, 94), P = 0.003. The median time period between the onset of symptoms and diagnosis was short (8 days) in patients presenting with thirst, but much longer for those with weight loss (294 days) and skin infections (463 days). Over a quarter of patients had raised blood glucose readings, which were not followed up in the two years before diagnosis was made. Most patients with type 2 diabetes are diagnosed in primary care. Many are asymptomatic at diagnosis. Earlier diagnosis of diabetes may be possible by considering diabetes in patients with weight loss and skin infections, and ensuring that borderline abnormal tests are adequately followed up. © 2008, Cambridge University Press. All rights reserved.