Combining Tests Leads to Better Prediabetes Detection

By LabMedica International staff writers
Posted on 16 Dec 2015

Image: Steps in the oral glucose tolerance test; if the blood sugar level is 140 to 199 mg/dL, the person has prediabetes or impaired glucose tolerance (IGT) (Photo courtesy of Penn Medicine).

The application of a screening test that is both robust and handy is vital for promptly ascertaining subjects with prediabetes. A robust and quick prediabetes diagnostic test can reduce overall societal costs of diabetes by motivating subjects with prediabetes to seek diabetes preventative care.

Fasting plasma glucose (FPG) and oral glucose tolerance (OGT) tests are greatly used in screening and diagnosing type 2 diabetes and while the OGT test is mostly recognized as the benchmark for diagnosing type 2 diabetes, but the test is laborious and uncomfortable to patients.

Scientists at Georgia State University (Atlanta, GA, USA) studied a group of participants whose ages ranged from 12 to 75 years with no missing values for age, height, weight, and assayed for OGT, FPG and HbA1c. Subjects were categorized as nondiabetic if they had FPG of less than 25 mg/dL or FPG of less than 199 mg/dL on a two-hour OGT test and HbA1c less than 6.5%. Prediabetes comprises impaired fasting glucose (IFG) expressed as FPG 100–125 mg/dL, impaired glucose tolerance (IGT) as OGT of 140–199 mg/dL, and HbA1c 5.7–6.4%.

The scientists found that the joint use of FPG and HbA1c test was associated with significantly higher proportion of subjects with prediabetes across age, race/ethnicity and BMI as compared to combined use of OGT and FPG, OGT and HbA1c. Overall prevalence of prediabetes using OGT + FPG, OGT + HbA1c, HbA1c + FPG, and OGT + FPG + HbA1c tests were 20.3%, 24.2%, 33%, and 34.3%, respectively. The study indicates prediabetes rates were higher using HbA1c + FPG tests compared to the traditionally used OGT + FPG tests.

The authors concluded that using a combination of HbA1c and FPG test in screening for prediabetes provides the benefits of individual test and decreases the risk of systematic bias inherent in using only HbA1c testing. This study proposes the need to redefine a basic and a practical way on the application of HbA1cin screening for prediabetes. The use of HbA1c test in detection of prediabetes in population and clinical settings should take into account patient race/ethnicity, gender, age, and body mass index (BMI). The study was published November 20, 2015, in the journal Frontiers in Public Health.

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Georgia State University