From the Guidelines
Falsely elevated hemoglobin A1c (HbA1c) readings can be caused by several factors, including iron deficiency anemia, hemoglobin variants, and certain medical conditions such as chronic kidney disease and liver disease, as well as recent blood transfusions and medications like high-dose aspirin and opioids. When interpreting HbA1c results, it is essential to consider these factors, as they can affect the accuracy of the test 1. Some of the conditions that can alter HbA1c measurement include:
- Iron deficiency anemia, which can prolong erythrocyte life span and expose the cell to glucose for a longer period, resulting in falsely elevated HbA1c levels 1
- Hemoglobin variants, which can result in falsely elevated or lowered HbA1c levels, depending on the assay used 1
- Chronic kidney disease, which can alter HbA1c measurement 1
- Recent blood transfusions, which can temporarily alter A1c levels by introducing red blood cells with different glucose exposure histories 2
- Conditions that affect red blood cell lifespan, such as hemolytic anemia or splenomegaly, which can lead to misleading results since A1c measures glucose bound to hemoglobin over the typical 120-day lifespan of red blood cells 2 It is crucial to use an A1C test that is certified by the NGSP and standardized to the DCCT assay to avoid misdiagnosis or missed diagnosis 2. In cases where there is marked discordance between measured A1C and plasma glucose levels, consideration should be given to using an assay without interference or plasma blood glucose criteria to diagnose diabetes 2. If you suspect your A1c result doesn't match your actual glucose control, discuss with your healthcare provider about alternative testing methods like fructosamine or glycated albumin tests, which measure shorter-term glucose control and may provide more accurate information in these situations.
From the Research
Causes of False High A1C
- Hemoglobin variants can interfere with laboratory readings, resulting in falsely high HbA1c measurements 3, 4, 5, 6, 7
- Specific hemoglobin variants that can cause false high A1c include: + Hb Santa Juana 3 + Hb Hirose (β-37Trp→Ser) and β-198A→G mutation in the promoter region of the gene 4 + Hemoglobin Wayne 5, 6, 7
- Increased red blood cell lifespan can also contribute to high HbA1c levels measured by various methods 4
- Hemoglobin antigenicity due to gene mutations may affect HbA1c levels measured by immunoassay 4
- Laboratory and patient-related factors, such as the measurement method used, can influence HbA1c measurements 4, 5, 6, 7