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12-09-2010 | Diabetes | Article

Optimal HbA1c screening interval for diagnosing Type 2 diabetes clarified

Abstract

Free abstract

MedWire News: Patients who have a glycated hemoglobin (HbA1c) level below 6.0% when tested for Type 2 diabetes do not require retesting at intervals shorter than 3 years, show study results.

However, those with an HbA1c between 6.0% and the diagnostic threshold of 6.5% are likely to benefit from more frequent testing, write the investigators in the journal Diabetes Care.

Osamu Takahashi (St Luke's International Hospital, Tokyo, Japan) and colleagues carried out a retrospective cohort study of 16,313 apparently healthy Japanese adults, aged 49.7 years on average, who were not taking glucose-lowering medication when they entered the study. The participants had annual health checks, including HbA1c testing, between 2005 and 2008.

At baseline, mean HbA1c was 5.4%. The team found that at 3 years the cumulative incidence of Type 2 diabetes was 0.05%, 0.05%, 1.20%, and 20.0% in participants with baseline HbA1c levels of less than 5.0%, 5.0-5.4%, 5.5-5.9%, and 6.0-6.4%, respectively.

There has been a recent shift towards using HbA1c for diagnosis of diabetes as it "integrates longer-term glucose levels and has better preanalytic stability" than fasting and post-glucose challenge blood glucose levels, say the authors.

The current diagnostic threshold for Type 2 diabetes is 6.5%, based on retinopathy risk, but optimal retesting intervals for at-risk individuals with an HbA1c level below 6.5% are less clear.

Takahashi and team say their results show that people with an HbA1c level below 6.0% are very unlikely to develop Type 2 diabetes during the subsequent 3 years and therefore more frequent testing than this is likely to be unnecessary.

They add that for those with an HbA1c level above 6.0% the risk is significantly greater, and therefore yearly testing in this group is not unreasonable.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Helen Albert