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Retinopathy Study Asks for Re-Examination of Diabetes Definition: Presented at ADA

By Bruce Sylvester

WASHINGTON, DC -- June 13, 2006 -- Correlation of retinopathy data and glycaemia suggests the possible need for a reevaluation of diagnostic definitions for diabetes, researchers reported at the American Diabetes Association 66^th Scientific Sessions (ADA).

"We looked at retinopathy rates as they were associated with fasting plasma glucose, 2-hour plasma glucose and haemoglobin A1c measures," said Yiling Cheng, MD, epidemiologist, Centers for Disease Control and Prevention, Division of Diabetes Translation, Atlanta, Georgia, United States, in a presentation on June 11^th. "Our findings suggest that we should look again at how we are defining diabetes using these measures."

The investigators evaluated data from 2,968 US adults aged 40 to 74 years who participated in the Third National Health and Nutrition Examination Survey (NHANES III). They compared the age- and sex-adjusted prevalence of any retinopathy as it was associated in the survey data with deciles of glycaemia.

Using a modified Airlie House Classification Scheme, the researchers identified subjects with retinopathy based on fundus photography. They correlated retinopathy data to the whole range of deciles of fasting plasma glucose, 2-hour plasma glucose, and glycated haemoglobin A1c (HbA1c).

For the purpose of their evaluation, the researchers combined the bottom 4 deciles of glucose measures as a lowest group to get a stable number of cases.

When they compared this lowest group with higher deciles for fasting glucose, the prevalence of retinopathy was 2.6 times (5.1%) higher for the 9^th decile (108-116.9 mg/dL) and 4.1 times (8.1%) higher for the 10^th decile (> 116.9 mg/dL).

Retinopathy prevalence was 2.4 times (3.6%) higher for the 7^th decile group of 2-h PG (119-130.9), 1.9 times (2.9%) higher for the 9^th decile (151-181.9 mg/dL), and 5.9 times (8.9%) higher for 10^th decile (> 181.9 mg/dL).

Measures of HbA1c did not discriminate retinopathy prevalence as clearly as the fasting and 2-hour plasma glucose measures.

Retinopathy is detectable even in the lowest deciles of glycaemia, but the prevalence of retinopathy is 5 times higher at a fasting glucose level of 120 mg/dL or a 2-hour plasma glucose > 180 mg/dL, according to the researchers. "These findings urge re-examination of existing definitions of diabetes," they wrote in their poster.

The study was sponsored by the Centers for Disease Control and Prevention.


[Presentation title: Fasting and 2-Hour Glucose and Glycated Haemoglobin Levels and Retinopathy in U.S. Adults: Searching for a Threshold. Abstract 886-P]

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