Yes, there are HbA1a, HbA1b, as well as HbA1c. The coding
breakdown is given below.
When hemoglobin is exposed to higher than normal levels of
glucose over time (blood sugar) it binds with it, this is called
glycation. And since the normal life span of red blood cells is
about 120 days, glycated hemoglobin can be used to assess the
average level of blood sugar during the preceding three months of
the test.
Hb - Hemoglobin
HbA - Adult hemogolbin (as contrasted to fetal hemoglobin,
HbF)
HbA0 - non-glycated hemoglobin.
HbA1 - glycated hemoglobin
HbA1a1 - Glycation with Fructose 1, 6 diphosphate
HbA1a2 - Glycation with Glucose 6 phosphate
HbA1b - Glycation with an unknown reaction partner
HbA1c - Glycation with D glucose
L HbA1c - denotes the labile HbA1c, or the aldimine fraction
S HbA1c - denotes the stable HbA1c, or the ketoamine
fraction.