OGTT, HbA1c identify different diabetes populations
medwireNews: The oral glucose tolerance test (OGTT) and glycated hemoglobin (HbA1c) measurements may identify different subpopulations of patients with type 2 diabetes, findings from the Whitehall II study suggest.
Presenting the results at the 54th EASD Annual Meeting in Berlin, Germany, Adam Tabak (Semmelweis University, Budapest, Hungary) reported that of the 384 cases of diabetes diagnosed by OGTT (unconfirmed diabetes; fasting blood glucose [FBG] ≥7.0 mmol/L or 2-hour blood glucose ≥11.1 mmol/L) in the study during 2002–2004 and 2007–2009, only 58.1% were confirmed by HbA1c over a median follow-up of 4.9 years.
He said that among people with unconfirmed diabetes, higher BMI and lower high-density lipoprotein cholesterol were predictors of a confirmed diabetes diagnosis by HbA1c. And patients who were initially diagnosed based on both 2-hour and FBG tests were more than three times as likely to receive a confirmed diabetes diagnosis as those who were diagnosed based on 2-hour glucose alone.
Tabak said that patients with HbA1c-confirmed diabetes had an elevated, albeit nonsignificant, risk for cardiovascular disease (CVD) compared with diabetes-free controls, with a hazard ratio (HR) of 1.25 after adjustment for factors including age, sex, smoking, cholesterol, and medication use. However, those with unconfirmed diabetes had a similar CVD risk as people without diabetes (adjusted HR=0.95), he reported.
In accordance with these findings, patients with HbA1c-confirmed diabetes were more likely to experience coronary heart disease (CHD) or chronic kidney disease (CKD) than control individuals, whereas those with unconfirmed diabetes had a similar risk for these outcomes relative to controls.
Together, these results indicate that “OGTT and [Hb]A1c identify different populations of patients with diabetes,” and OGTT cases that are not subsequently confirmed by HbA1c do not have an elevated risk for CVD, CHD, or CKD, said Tabak.
And he concluded that “our findings might argue that those people who have OGTT-based diabetes that is not confirmed by [Hb]A1c during follow-up […] can be lost as diabetes cases, because their micro- and macrovascular risk is similar to the background population.”
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