Objective — To provide the first population-based estimates of prediabetes and undiagnosed type 2 diabetes prevalence in Canada.
Research Design and Methods — We combined two fasting subsamples of the Canadian Health Measures Survey, which were restricted to nonpregnant adults ≥20 years of age (N = 3,494). Undiagnosed diabetes was defined as not having self-reported type 2 diabetes but having blood glucose measures that met Canadian guidelines (i.e., fasting plasma glucose [FPG] level of ≥7.0 mmol/L or hemoglobin A1c [HbA1c] level of ≥6.5% [≥48 mmol/mol]). Prediabetes was defined as an FPG level of ≥6.1 and <7.0 mmol/L or an HbA1c level of ≥6.0% and <6.5% (≥42 and <48 mmol/mol). All estimates were weighted using survey sampling weights. CIs were calculated with the bootstrap method.
Results — According to FPG levels, the prevalence of undiagnosed type 2 diabetes in Canadian adults was 1.13% (95% CI 0.79, 1.62), contributing to ∼20% of total type 2 diabetes prevalence (5.62 [95% CI 4.52, 6.95]). Compared with FPG levels, the undiagnosed prevalence was greater using HbA1c level as a criterion (3.09% [95% CI 1.97, 4.81]), ∼41% of the total number of cases of diabetes (7.55 [95% CI 5.98, 9.49]). The HbA1c-only criterion resulted in a threefold increase in prediabetes prevalence overall and a sixfold increase among females (FPG 2.22%, HbA1c 13.31%). Screening based on FPG-only identified older undiagnosed case patients, with a mean age of 58.7 years (95% CI 59.9, 63.4). Similarly, using HbA1c identified younger individuals with prediabetes, with reduced BMI and waist circumference compared with FPG levels.
Conclusions — In this first study of a nationally representative sample with biospecimen measures, we found that the prevalence of undiagnosed type 2 diabetes and prediabetes was significantly higher using HbA1c levels compared with FPG levels. Further evaluation is needed to fully assess the impact of using the HbA1c criterion.
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Screening and prevention