Should A1c (hemoglobin A1c) be checked for screening in patients with a history of hypertension and hypercholesterolemia?

A1c Screening for Patients with Hypertension and Hypercholesterolemia

Yes, A1c testing should be performed for screening in patients with a history of hypertension and high cholesterol, as these conditions are clear risk factors that warrant diabetes screening according to current guidelines. 1

Evidence-Based Rationale

The US Preventive Services Task Force (USPSTF) explicitly recommends screening for type 2 diabetes in adults with hypertension or hyperlipidemia with a "B" recommendation, indicating moderate certainty of moderate to substantial benefit 1. This recommendation has been consistently maintained in guidelines for nearly two decades.

The American Diabetes Association (ADA) reinforces this position in their 2022 Standards of Medical Care, specifically listing hypertension (≥140/90 mmHg or on therapy) and HDL cholesterol <35 mg/dL and/or triglyceride level >250 mg/dL as risk factors that warrant diabetes screening 1.

Screening Method

When screening these patients, A1c is an appropriate test for the following reasons:

• Does not require fasting
• Reflects average glycemia over approximately 3 months
• Has standardized measurement protocols
• Cut point of ≥6.5% is diagnostic for diabetes 1

Screening Algorithm for Patients with Hypertension and Hypercholesterolemia

1. Initial Screening:

   • Perform A1c test (preferred due to convenience of not requiring fasting)
   • Alternative: Fasting plasma glucose (FPG) or 2-hour post-load glucose test

2. Interpret Results:

   • A1c ≥6.5%: Diagnostic for diabetes (should be confirmed with repeat testing)
   • A1c 5.7-6.4%: Prediabetes (increased risk)
   • A1c <5.7%: Normal

3. Follow-up Based on Results:

   • If diabetes diagnosed: Begin appropriate management
   • If prediabetes identified: Test yearly and implement preventive interventions
   • If normal: Repeat testing every 3 years 1, 2

Clinical Importance

Screening these patients is particularly important because:

• Patients with hypertension and diabetes benefit from lower blood pressure targets and specific antihypertensive medications 1
• For patients with hyperlipidemia, detecting diabetes substantially improves cardiovascular risk assessment and management 1
• Early detection allows for earlier intervention that may reduce microvascular complications 3

Important Considerations and Pitfalls

• A1c may be inaccurate in conditions affecting red blood cell turnover (hemolytic anemia, iron deficiency, recent blood loss, hemoglobinopathies) 1, 2
• Point-of-care A1c testing should not be used for diagnosis due to potential accuracy limitations 2
• In cases where A1c is unreliable, use glucose-based testing methods instead 1
• A single abnormal test result should be confirmed with repeat testing before making a definitive diagnosis 1

Documentation Considerations

When ordering A1c for screening purposes in patients with hypertension and hyperlipidemia, document these conditions as they meet medical necessity criteria for testing 2. Appropriate ICD-10 codes include I10 for essential hypertension and E78.5 for dyslipidemia.

By screening patients with hypertension and hypercholesterolemia for diabetes, you can identify those at risk earlier, implement appropriate interventions, and potentially reduce both microvascular and macrovascular complications.