Sacks 2011: Laboratory Guidelines for Diabetes

Background

Dr. David B. Sacks and the ADA/NACB Laboratory Medicine Practice Guidelines Expert Panel published these comprehensive guidelines in Diabetes Care (PMID: 21617108), standardizing laboratory testing for diabetes diagnosis and management.

Study Design

Expert consensus guidelines based on systematic evidence review for laboratory practices in diabetes care.

Key Findings

HbA1c for diagnosis:

HbA1c Level	Interpretation
<5.7%	Normal
5.7-6.4%	High risk (prediabetes)
≥6.5%	Diabetes (requires confirmation)

Standardization requirements:

• •NGSP-certified methods only
• •CV <3% for precision
• •Annual proficiency testing

Conditions affecting HbA1c:

Condition	Effect on A1C
Hemoglobinopathies	Variable (may interfere)
Anemia/hemolysis	Falsely low
Iron deficiency	Falsely high
Chronic kidney disease	Variable
Recent transfusion	Inaccurate

Treatment targets:

• •General: <7% (individualized)
• •Low hypoglycemia risk: <6.5%
• •Limited life expectancy: <8%

Mechanistic Insights

HbA1c standardization was critical because:

• •Different methods gave different results
• •NGSP calibration ensures comparability
• •Allows diagnosis and monitoring with single test

Clinical Implications

Laboratories must use NGSP-certified methods. Clinicians should recognize conditions affecting HbA1c accuracy. Alternative markers (fructosamine, glycated albumin) available when HbA1c unreliable.

Metabolic Health Perspective

For metabolic optimization, HbA1c <5.7% is the goal. However, some metabolically healthy low-carb individuals may have slightly higher fasting glucose with low HbA1c—context matters. CGM provides complementary information about glucose variability.