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Study Evaluates Best Way to Diagnose Prediabetes

Mar 31, 2018
 

Researchers compare fasting BG, HbA1c and 2-hour plasma glucose test.

Should we be using the HbA1c or the fasting blood sugar  to diagnose prediabetes? According to a new study, prediabetes defined by HbA1c can lead to a worse prognosis.

 

With 100 million people in the U.S. and 90% unaware that they have prediabetes, we need to determine the best way to educate them as to what they need to do to prevent or delay diabetes.

In a new study, researchers found that adults with prediabetes defined by HbA1c levels were more likely to have an increased risk for cardiovascular disease or all-cause mortality compared with adults with prediabetes defined by fasting plasma glucose or 2-hour plasma glucose, study data show.

Dorte Vistisen, MSc, PhD, senior research and team leader at the Steno Diabetes Center Copenhagen in Denmark, and colleagues evaluated data from the Whitehall II study on 5,427 adults ages 50 to 79 years without diabetes who were followed for a median of 11.5 years to compare the risks for CVD and all-cause mortality in subgroups of prediabetes defined by FPG, 2-hour plasma glucose or HbA1c.

Prediabetes was defined using WHO/International Expert Committee (IEC) criteria (FPG, 6.1-6.9 mmol/L and/or HbA1c, 6% to 6.4%) and ADA criteria (FPG, 5.6-6.9 mmol/L and/or HbA1c, 5.7% to 6.4%). Additional measures of 2-hour plasma glucose were used to define prediabetes in a subset of 4,730 participants.

Overall, 7.4% of participants had prediabetes using WHO/IEC FPG criteria (mean age, 61.8 years; 85.6% men; 90.6% white), 5.3% by WHO/IEC HbA1c criteria (mean age, 65.5 years; 67.3% men; 80.1% white), 26.1% using ADA FPG criteria (mean age, 61.1 years; 83.9% men; 94.5% white) and 17.3% using ADA HbA1c criteria (mean age, 64.8 years; 66.8% men; 83.4% white).

During follow-up, 21.3% of participants with prediabetes defined by WHO/IEC criteria developed CVD or died compared with 18.5% of participants with prediabetes defined by the ADA criteria. The incident rates were 54% higher in participants with prediabetes defined by the WHO/IEC criteria and 37% higher in participants with prediabetes defined by the ADA criteria compared with participants with normoglycemia.

The rate of events was higher in participants with prediabetes defined by the WHO/IEC FPG criteria (19.4 per 1,000 person-years) compared with those with prediabetes defined by ADA FPG criteria (16.5 per 1,000 person-years); after full adjustment, incidence rates were the same level as those of participants with normoglycemia. The event rate was higher in participants with prediabetes defined by the WHO/IEC HbA1c criteria (29.5 per 1,000 person-years) compared with those with prediabetes defined by ADA HbA1c criteria (26 per 1,000 person-years). In the subset of participants with prediabetes defined by 2-hour plasma glucose, the event rate was 44% higher compared with participants with normoglycemia. However, after full adjustment for previous CVD, smoking, total cholesterol, HDL cholesterol, systolic blood pressure, and use of antihypertensive treatment, the differences in incidence rates became nonsignificant.

“People with prediabetes are at increased risk of developing CVD or die prematurely. However, the amount of risk depends on how prediabetes is defined,” Vistisen said, adding that “among this study population aged 50 to 80 years, prediabetes defined by HbA1c was associated with a higher risk of CVD and premature death than prediabetes defined by fasting glucose or 2-hour glucose following an OGTT. However, in general, the excess risk among people with prediabetes is mainly explained by the clustering of other cardiometabolic risk factors associated with hyperglycemia.”

Practice Pearls:

  • Time that a patient can maintain normal blood sugars plays a major role in preventing diabetes.
  • Although fewer individuals with prediabetes were identified by HbA1c than by FPG criteria, the ability to predict progression to diabetes was stronger for HbA1c than for FPG.
  • Future research should focus on evaluating the joint effect of prediabetes with other easily measured CV risk factors on predicting overall risk of CVD and mortality.

Reference:

Diabetes Res Clin Pract. 2016 Aug;118:105-11. doi: 10.1016/j.diabres.2016.06.009. Epub 2016 Jun 18.