Concordance between two glucose tests low for diagnosing diabetes in at-risk individuals
The glycated haemoglobin (HbA1c) test and oral glucose tolerance test (OGTT) appear to have low concordance for diagnosing prediabetes or diabetes in overweight or obese men and women, a recent study reports.
Researchers enrolled 949 overweight or obese outpatients at risk of diabetes (mean age, 50 years; 69.55 percent female), who underwent both OGTT and the HbA1c test for diagnosis of prediabetes or type 2 diabetes (T2D). They examined concordance between the two tests, focusing on possible gender‐related differences.
Results for OGTT were negative in 76 percent of the overall population, positive for prediabetes in 19 percent and positive for T2D in 5 percent. On the other hand, HbA1c assay returned negative results in 55 percent of the population and positive results for prediabetes and T2D in 41 percent and 4 percent, respectively.
Compared with OGTT, the HbA1c test identified more patients with prediabetes in both sexes (42 percent vs 22 percent in males; 40 percent vs 18 percent in females). The two tests did not achieve high concordance (60 percent of total tests in both sexes).
In prediabetes/T2D patients diagnosed by OGTT, post‐OGTT insulin levels and the Homeostasis Model Assessment Index were significantly higher than those seen in patients diagnosed by HbA1c. Furthermore, those diagnosed using HbA1c were significantly older and showed higher uric acid compared with participants whose OGTT and HbA1c tests returned negative results.
The low concordance between the two tests may reflect the fact that each test can measure different pathophysiological aspects of dysglycaemia, according to the researchers. A single positive test result may not suffice when diagnosing possible altered conditions, suggesting that the “diagnostic thresholds” might be reconsidered in view of the discordance observed in the present study.