What is the screening and diagnostic flow for diabetes mellitus according to DOH/WHO guidelines?

DOH/WHO PEN Diabetes Mellitus Screening & Diagnostic Flow

The diagnosis of diabetes mellitus requires confirmation of hyperglycemia using standardized plasma glucose criteria, with any single abnormal test requiring repeat testing on a separate day unless classic symptoms are present. 1

Diagnostic Criteria (Any ONE of the following)

1. Fasting Plasma Glucose (FPG) ≥126 mg/dL (7.0 mmol/L)

• Fasting defined as no caloric intake for at least 8 hours 1
• Must be measured in venous plasma in an accredited laboratory 2
• Requires confirmation with repeat testing on a separate day 1

2. Random Plasma Glucose (RPG) ≥200 mg/dL (11.1 mmol/L) WITH Classic Symptoms

• Classic symptoms include: polyuria, polydipsia, weight loss, blurred vision, or fatigue 2
• This is the ONLY criterion that does NOT require repeat testing for diagnosis 1
• If symptoms are present with RPG ≥200 mg/dL, diagnosis is confirmed immediately 3

3. HbA1c ≥6.5%

• Must be performed in a laboratory using NGSP-certified method standardized to DCCT assay 2, 1
• Requires confirmation with repeat testing on a separate day 1
• Point-of-care HbA1c should be restricted to FDA-approved devices at CLIA-certified laboratories 2

4. 2-Hour Plasma Glucose ≥200 mg/dL (11.1 mmol/L) During 75-g OGTT

• Patient must fast 8 hours before test 2
• Patient should consume at least 150g carbohydrates daily for 3 days preceding test 1
• Requires confirmation with repeat testing on a separate day 1

Confirmation Pathway

Single Test Result Above Threshold:

1. If asymptomatic: Repeat the SAME test on a different day 1
2. If symptomatic with RPG ≥200 mg/dL: Diagnosis confirmed immediately, no repeat needed 1, 3
3. If HbA1c ≥6.5% is present alongside FPG ≥126 mg/dL: Diagnosis confirmed with single blood draw 1

Two Different Tests Both Above Threshold:

• Diagnosis is confirmed without need for repeat testing 1

Discordant Results (One test positive, one negative):

• Repeat the test that was above the diagnostic threshold 1

Prediabetes Categories (Increased Risk for Diabetes)

Impaired Fasting Glucose (IFG):

• FPG 100-125 mg/dL (5.6-6.9 mmol/L) 1

Impaired Glucose Tolerance (IGT):

• 2-hour OGTT 140-199 mg/dL (7.8-11.0 mmol/L) 1

At-Risk HbA1c:

• HbA1c 5.7-6.4% 1

Critical Pitfalls to Avoid

Laboratory Requirements:

• Never use point-of-care glucose meters for diagnosis—they lack sufficient accuracy 4
• All diagnostic testing must be performed in accredited laboratories using venous plasma 2

HbA1c Limitations:

• Do NOT use HbA1c for diagnosis in: hemoglobinopathies, anemias, pregnancy, recent blood loss/transfusion, hemodialysis, or erythropoietin therapy 1
• In these conditions, use ONLY plasma glucose criteria 1

Biological Variation:

• Fasting glucose has 4.8-6.1% day-to-day variation in the same person 4
• A true FPG of 100 mg/dL could measure 87-113 mg/dL on different days 4
• This is why confirmation testing is essential 1

Common Errors:

• Inadequate fasting (<8 hours) invalidates FPG results 4
• Not confirming abnormal results leads to misdiagnosis 4
• Random glucose 140-180 mg/dL has high specificity (92-98%) but low sensitivity (39-55%)—requires definitive testing 2

Screening Recommendations

Who to Screen:

• Adults ≥45 years: screen every 3 years if normal 1
• Adults <45 years with BMI ≥25 kg/m² PLUS one or more risk factors: screen at any age 1
• Adults with sustained blood pressure >135/80 mmHg: screen for diabetes 2

Risk Factors Requiring Earlier Screening:

• Physical inactivity 2
• First-degree relative with diabetes 2
• High-risk ethnicity 2
• History of gestational diabetes or delivery of baby >9 lb 2
• Hypertension or cardiovascular disease 2
• HDL <35 mg/dL or triglycerides >250 mg/dL 2
• Polycystic ovary syndrome 2
• Previous HbA1c ≥5.7%, IFG, or IGT 2