Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (301 page)

SICKLE CELL–PERSISTENT HIGH FETAL HEMOGLOBIN

   Definition

Condition seen in 1 in 25,000 African Americans but also frequent in Arab populations. May be mimicked in patients with sickle cell anemia responding to hydroxyurea therapy. Clinical picture and findings intermediate between sickle cell anemia and trait.

   Laboratory Findings

   Hb electrophoresis: HbF is 20–40%; HbA1 and A2 are absent; HgS is approximately 65%.

   RBC: HbF is unevenly distributed among RBC.

SICKLE CELL–HEMOGLOBIN D DISEASE

   Definition

Condition resembling HbS/HbC disease; less severe than sickle cell anemia. Found in 1 in 20,000 individuals of African ancestry. Clinically a mild syndrome.

   Laboratory Findings

   Intermediate between those of sickle cell anemia and sickle cell trait.

   Hb electrophoresis cannot distinguish HbS from HbD at alkaline pH but can be separated at pH 6.2.

Suggested Readings

Vichinsky EP, Mahoney DH Jr. Diagnosis of sickle cell syndromes. UpToDate. In: Basow DS (ed). Waltham, MA: UpToDate, Inc.; 2013.

Ware RE. How I use hydroxyurea to treat young patients with sickle cell anemia.
Blood.
2010;115:5300–5311.

HEMOGLOBIN C DISEASE

   Definition

A hemoglobinopathy prevalent in individuals with ancestral roots in West Africa.

Autosomal transmission.

   HbC trait: found in 2% of African Americans, less frequently in other groups; asymptomatic, no anemia.

   Homozygous HbC disease: mild hemolytic anemia.

   Laboratory Findings

   HbC trait: Hb variant analysis shows 50% HbA1 and 30–40% HbC.