Should I order an HbA1c (Hemoglobin A1c) test on a 63-year-old female?

HbA1c Testing for a 63-Year-Old Female

Yes, you should order an HbA1c test for a 63-year-old female as part of routine diabetes screening, as recommended by the American Diabetes Association guidelines. 1

Rationale for HbA1c Testing

HbA1c testing is appropriate for this patient based on several key factors:

• Age: At 63 years old, this patient is well above the recommended age threshold (45 years) for diabetes screening in adults 1, 2
• Convenience: HbA1c testing offers greater convenience as it:
  • Does not require fasting
  • Reflects average glycemia over the preceding 2-3 months
  • Has greater preanalytical stability than plasma glucose measurements 1, 3

Testing Protocol

When ordering the HbA1c test:

• Use a laboratory method that is NGSP certified and standardized to the DCCT assay

• Interpret results according to these diagnostic thresholds:

  • Normal: <5.7% (<39 mmol/mol)
  • Prediabetes: 5.7-6.4% (39-47 mmol/mol)
  • Diabetes: ≥6.5% (≥48 mmol/mol) 1

• If the result is abnormal, confirm with a repeat HbA1c test or an alternative test (FPG or OGTT) 1

Important Considerations and Limitations

Be aware of conditions that may affect HbA1c accuracy:

• Hemoglobinopathies: Certain hemoglobin variants can interfere with some HbA1c assays 1
• Altered red blood cell turnover: In conditions with increased red cell turnover (hemolysis, recent blood loss/transfusion, erythropoietin therapy), HbA1c may be falsely lowered 1, 2
• Age effect: HbA1c levels increase with age independent of glucose levels (approximately 0.1% per decade), which may affect diagnostic specificity in older adults 4

If any of these conditions are present, consider using fasting plasma glucose or 2-hour OGTT instead.

Follow-up Recommendations

Based on the test results:

• Normal result: Repeat testing in 3 years 1
• Prediabetes (5.7-6.4%): Annual testing and consider lifestyle interventions 1
• Diabetes (≥6.5%): Confirm with a second test (unless clear clinical evidence of diabetes) and initiate appropriate management 1

Additional Risk Assessment

While ordering HbA1c, consider evaluating for other diabetes risk factors:

• BMI (≥25 kg/m² or ≥23 kg/m² in Asian Americans)
• Family history of diabetes
• High-risk ethnicity
• History of cardiovascular disease
• Hypertension
• Dyslipidemia
• Polycystic ovary syndrome 1, 2

The presence of these risk factors increases the importance of screening and may influence the frequency of follow-up testing.