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22-01-2012 | Diabetes | Article

HbA1c unreliable for detecting prediabetes and diabetes

Abstract

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MedWire News: Glycated hemoglobin (HbA1c) is generally insensitive for the diagnosis of prediabetes and diabetes, study findings suggest.

"This has implications for current and future diabetes prevention programs, vascular risk management, and for clinical advice given to people with prediabetes based on fasting glucose data," say the study authors.

There has been intense debate recently about the revised criteria for the diagnosis of diabetes, write the researchers in Diabetes Research and Clinical Practice.

The American Diabetes Association (ADA) has proposed a diabetes diagnosis based on an HbA1c level of 6.5% or more, and a prediabetes diagnosis, in cases of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), based on an HbA1c of 5.7-6.4%.

Others, say the authors, have suggested an HbA1c range of 6.1-6.4% as indicating an increased risk for diabetes.

Led by Max Bachmann (University East Anglia, Norwich, UK), the team measured fasting plasma glucose (FPG) and HbA1c in 3906 adults as part of the University of East Anglia-Impaired Fasting Glucose program.

Each participant included had at least one of the following risk factors for glucose intolerance: a first degree relative with Type 2 diabetes, body mass index (BMI) of more than 25 kg/m2, waist circumference of more than 95 cm in men and more than 80 cm in women, history of coronary heart disease, history of gestational diabetes, or a clinical report or self-report that they have IFG.

The study revealed that 539 (13.8%) of the participants screened had IFG, as defined by the new ADA criteria (FPG 5.6-6.9 mmol/L), 176 (4.5%) had IFG according to the pre-2010 ADA criteria (6.1-6.9 mmol/L), and 81 (2.1%) had diabetes.

The researchers report that with FPG 5.6-6.9 mmol/L as the reference standard, the HbA1c level 5.7-6.4% was 63% sensitive and 81% specific in diagnosing IFG, while the HbA1c level 6.1-6.4% was 21% sensitive and 98% specific.

An HbA1c level of 6.5% or more was 61% sensitive and 99% specific in diagnosing Type 2 diabetes.

"Defining prediabetes at a lower HbA1c threshold of 5.7% instead of 6.1% increases its sensitivity in diagnosing IFG," say Bachmann et al.

But the current ADA definition of prediabetes based on HbA1c (5.7-6.4%) would still fail to detect almost 40% of people currently classified as having impaired fasting glucose, they conclude.

MedWire (http://www.medwire-news.md/) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2012

By Sally Robertson

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