Measurement of hemoglobin A1c may be falsely elevated or falsely depressed in a patient with a hemoglobinopathy. Attempting to judge glucose control as a result will be misleading, and an alternative strategy should be used for the patient.
The variations depend on:
(1) the method of measuring hemoglobin A1c
(2) the type of hemoglobinopathy
(3) the patient
Some analytical methods are more likely to give misleading results than others.
(1) Affinity chromatography may be affected. Some results can be explained by changes in peak migration, which are not measured.
(2) Mass spectroscopy is the most accurate method.
Hemoglobinopathies vary in the effect.
(1) a hemoglobinopathy with reduced hemoglobin A1 may be problematic
(2) sickling of red cells can occur in some test conditions
Patients may have varying degrees of anemia depending on the type of hemoglobinopathy.
(1) Glycosylation of hemoglobin tends to increase with red blood cell age.
(2) Anemia associated with reduced red blood cell lifespans may have a higher percentage of young erythrocytes.
(3) If the spleen is involved, removal of vesicles from the erythrocytes can reduce the hemoglobin content of red blood cells over time.
(4) The absence of a spleen may alter the lifespan of red blood cells.
(5) Iron and vitamin deficiencies may affect the rate of hemoglobin glycation.
The equations converting a percentage of hemoglobin A1c to mean glucose levels may be invalid in patients with hemoglobinopathies, since the equations were developed in populations with a high prevalence of hemoglobin AA.
Alternatives to hemoglobin A1c include:
(1) glycosylated albumin
(2) fructosamine
