May 6, 2008
A New Look at Screening and Diagnosing Diabetes Mellitus

Diabetes is under-diagnosed. About 1/3 of people with diabetes do not know they have it, and the average lag between onset and diagnosis is 7 years. A report published online May 6, 2008 in the Journal of Clinical Endocrinology & Metabolism (& to be published in the July print issue) reconsiders the criteria for diagnosing diabetes, and recommends screening criteria, in order to make case-finding easier for clinicians and patients.

Based on their research and deliberations members of the expert panel recommend  that hemoglobin A1c (HbA1c) testing, an indicator of blood sugar levels over the past 3 months, should be used as a screening and diagnostic test for diabetes.

The main factors in support of using HbA1c as a screening and diagnostic test include:

• HbA1c does not require patients to be fasting
• HbA1c reflects longer-term glycemia than does plasma glucose
• HbA1c laboratory methods are now well standardized and reliable
• Errors caused by non-glycemic factors affecting HbA1c such as hemoglobinopathies are infrequent and can be minimized by confirming the diagnosis of diabetes with a plasma glucose (PG)-specific test.

The recommendations:

• Screening standards should be established that prompt further testing and closer follow-up, including fasting PG ≥ 100 mg/dL, random PG ≥ 130 mg/dL or HbA1c > 6.0%
• HbA1c ≥ 6.5 – 6.9% confirmed by a PG-specific test (FPG or OGTT) should establish the diagnosis of diabetes
• HbA1c ≥ 7%, confirmed by another HbA1c or a PG-specific test (FPG or OGTT) should establish the diagnosis of diabetes.

The recommendations are offered for consideration of the clinical community and interested associations & societies.

Explanation of terms:
PG – Plasma Glucose
FPG Test (Fasting Plasma Glucose Test) – this test measures your blood glucose after you have gone at  
                                                                       least 8 hours without eating
OGTT (Oral Glucose Tolerance Test) – The OGTT requires you to fast for at least 8 hours before the
                                                                test. Your plasma glucose is measured immediately before  
                                                                      and 2 hours after you drink a liquid containing 75 grams of
                                                                glucose dissolved in water.                                            

For more info: see SL Issues 8 & 9.