Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (977 page)

   HbD (hemoglobinopathy that may also be found in combination with HbS or thalassemia)

   HbE

   HbS (sickle trait or disease)

Decreases In HbA
₂

   α-Thalassemia

   Erythroleukemia

   Iron deficiency anemia (untreated)

   Sideroblastic anemia

   Limitations

   HbA
₂
and HbF levels should be considered in conjunction with family history plus laboratory data, including serum iron, TIBC, ferritin, red cell morphology, hemoglobin, Hct, and MCV.

   Blood transfusions may temporarily obscure or dilute abnormal Hb.

   When using HPLC, when HbA
₂
exceeds 10%, the presence of HbE or other Hb with similar resolution should be investigated.

   Quantitation of hemoglobins is performed optimally after 1 year of age.

   Hb Lepore arises from an unequal crossing-over and recombination event between adjacent δ and β globin genes. The resulting Hb has the mobility of HbS on alkaline electrophoresis and HbA on acid electrophoresis.