HbA1c testing

Overview of Treatment

The HbA1c test (glycated hemoglobin measurement) is a blood test used to assess a patient's average blood glucose levels over the past 2 to 3 months. This test measures the degree of hemoglobin in red blood cells that has bonded with glucose, providing an objective indicator of long-term blood sugar control. It is primarily used for diagnosing diabetes, monitoring treatment effectiveness, and screening high-risk populations for hyperglycemia. Unlike immediate blood glucose levels, HbA1c reflects long-term metabolic status, making it an indispensable tool in international medical guidelines.

Types of Treatment and Mechanisms

The HbA1c test is a biochemical assay based on the principle that glucose in the blood binds with hemoglobin in red blood cells to form glycated hemoglobin. The proportion of this binding correlates positively with blood glucose concentration, and since the average lifespan of red blood cells is about 120 days, HbA1c levels can reflect the average blood glucose over the previous 2 to 3 months. Currently, high-performance liquid chromatography (HPLC) or immunoturbidimetric methods are used for quantification, with results expressed as a percentage (%) or mmol/mol.

Indications

This test is suitable for diagnosing diabetes, adjusting treatment plans, monitoring gestational diabetes, and assessing the risk of prediabetes. According to WHO guidelines, an HbA1c ≥6.5% can be used as one of the diagnostic criteria for diabetes. Additionally, regular testing every 3 to 6 months in diabetes management can effectively evaluate the efficacy of medications, diet, or exercise programs. In special populations such as the elderly or patients with chronic kidney disease, HbA1c can also assist in interpreting metabolic control status.

Usage and Dosage

The test involves venous blood draw, requires no fasting, and can be performed simultaneously with other blood tests. The frequency of testing depends on the condition: screening once a year for those not diagnosed with diabetes, and every 3 to 6 months for diagnosed patients. In special situations such as pregnancy or use of medications affecting hemoglobin metabolism, physicians may adjust the testing frequency or recommend alternative assessments.

Benefits and Advantages

• Non-invasive test, obtaining long-term blood glucose trends with a simple blood draw
• Not affected by immediate blood glucose fluctuations caused by diet, stress, or acute illness
• Provides objective standardized data, facilitating comparison across different healthcare settings

Risks and Side Effects

The risk associated with this test is extremely low, but potential sources of error include:

• Specific hemoglobin variants (such as HbS, HbC) can interfere with some testing methods
• Recent transfusions or erythropoietin therapy may lead to skewed results

If abnormal values are observed, clinicians should interpret results in conjunction with clinical data to avoid misdiagnosis.

Precautions and Contraindications

Contraindications include:

• Severe hemolytic anemia or hemoglobinopathies
• Recent large-volume blood transfusions

Special precautions:

Patients should inform their doctor of any medications they are taking (such as vitamin C or E, which may interfere with certain tests), and recent history of bleeding or transfusions. During pregnancy, HbA1c may be falsely low due to increased plasma volume, so it should be interpreted alongside fasting blood glucose levels.

Interactions with Other Treatments

HbA1c is a diagnostic tool and does not directly interact with medications, but the following situations require attention:

• Use of erythropoiesis-stimulating agents (e.g., EPO) may cause falsely low readings
• Iron deficiency anemia may affect accuracy
• When combined with C-peptide measurement, blood glucose curves, and other tests, comprehensive analysis is necessary to avoid misinterpretation

Treatment Efficacy and Evidence

Multiple large studies have confirmed that reducing HbA1c by 1% can decrease the risk of diabetes-related complications by approximately 20%. The ADA 2021 diagnostic criteria explicitly list HbA1c ≥6.5% as the gold standard for diagnosing diabetes. In clinical practice, combining HbA1c with self-monitoring of blood glucose (SMBG) can enhance the precision of treatment plans.

Alternative Methods

If HbA1c testing is not feasible, the following alternatives can be considered:

• Oral glucose tolerance test (OGTT): assesses glucose metabolism function
• Fasting blood glucose: reflects blood glucose status after 8 to 12 hours of fasting
• Continuous glucose monitoring system (CGM): provides dynamic data over 7 to 14 days

However, each method has limitations, such as OGTT being time-consuming, fasting blood glucose only reflecting a momentary value, and the choice depending on clinical needs.

 

Frequently Asked Questions

Is fasting required before HbA1c testing?

No, fasting is not required before HbA1c testing. This test mainly measures the average blood glucose over the past 2 to 3 months and is unaffected by postprandial blood glucose fluctuations. However, if other blood tests such as fasting blood glucose are also needed, follow your doctor’s instructions regarding timing.

How will doctors adjust treatment if HbA1c results are abnormal?

If HbA1c exceeds the target range, doctors may adjust medication doses, recommend stricter dietary control, or increase exercise frequency based on the cause. If results remain unstable, further evaluation for other complications or lifestyle factors may be necessary.

What conditions may lead to inaccurate HbA1c results?

Severe anemia, hemoglobinopathies, or recent transfusions can affect HbA1c accuracy. Additionally, pregnancy-related increased plasma volume can cause data shifts, and alternative indicators may be used to assess blood glucose control during this period.

What is the difference between HbA1c and daily blood glucose monitoring?

HbA1c reflects long-term blood glucose trends, while daily blood glucose monitoring shows immediate values. Both should be used together: HbA1c for evaluating treatment efficacy, and immediate blood glucose for adjusting diet, exercise, or insulin doses. They are complementary and should not be used in isolation.

What are the long-term benefits of regular HbA1c testing for diabetic patients?

Regular monitoring of HbA1c allows early detection of blood sugar control trends, preventing the progression of chronic complications such as retinopathy or nephropathy. Studies show that maintaining HbA1c within target ranges (e.g., <7%) significantly reduces cardiovascular risk and delays disease progression.