Best Screening Test for Diabetes

Introduction to Screening Tests

The American Diabetes Association recommends fasting plasma glucose (FPG) as the best screening test for diabetes because it is easier and faster to perform, more convenient and acceptable to patients, less expensive, and more reproducible than other screening tests 1, 2, 3

FPG has greater convenience and lower cost compared to the 2-hour oral glucose tolerance test (OGTT), which requires multiple blood draws and prolonged patient time 2, 3, 4
FPG has better reproducibility with less intraindividual variation than the 2-hour plasma glucose test 5, 4
FPG has similar predictive value for development of microvascular complications of diabetes compared to OGTT 5, 4

FPG ≥126 mg/dL indicates diabetes and should be confirmed with repeat testing on a different day 1, 2, 3, 6

The 2014 American Diabetes Association guidelines expanded acceptable screening tests to include A1C and OGTT alongside FPG 1
OGTT may identify more individuals as diabetic compared to FPG, but has major disadvantages including being more expensive, time-consuming, less convenient, and having the highest intraindividual variability of all tests 1, 2, 5, 4

The American College of Physicians recommends screening adults 40-70 years of age who are overweight or obese (BMI ≥25 kg/m²), repeating every 3 years if normal 8
Additional screening criteria include age ≥45 years, physical inactivity, first-degree relative with diabetes, high-risk ethnicity, history of gestational diabetes or delivering a baby >9 lb, hypertension, HDL cholesterol <35 mg/dL or triglycerides >250 mg/dL, previous A1C ≥5.7%, impaired glucose tolerance, or impaired fasting glucose 1, 3, 4, 7

To ensure accurate FPG results, use proper collection tubes containing glycolytic inhibitors, process samples promptly, measure in accredited laboratory using enzymatic methods, and define fasting as no caloric intake for at least 8 hours 1, 2, 6

Always confirm abnormal screening results with repeat testing on a different day, especially for borderline values 1, 2, 9
If two different tests (e.g., A1C and FPG) are both above diagnostic thresholds, diagnosis is confirmed without repeat testing 1