Table 1.

Sickle Cell Disease: Diagnostic Test Results

Abnormal Globin Beta Chain Variants 1Hemoglobins Identified by Age Six Weeks 2PhenotypeHematologic Studies by Age Two Years
MCV 3, 4HbA2 5
S/S (βSβS)HbF, HbSHemolysis & anemia by age 6-12 mosN<3.6%
S/β0-thal (βSβ0)>3.6%
S/β+-thal (βSβ+)HbF, HbS, HbAMilder hemolysis & anemia>3.6%
S/C (βSβC)HbF, HbS, HbCN or ↓<3.6%

Table shows typical results; exceptions occur. Less common genotypes (e.g., Hb S/D, Hb S/O, Hb S/E) are not included.

↑ = increased; ↓ = decreased; β = beta; HbA = adult hemoglobin; HbC = hemoglobin C; HbF = fetal hemoglobin; HbS = sickle hemoglobin; MCV = mean corpuscular volume; N = normal; thal = thalassemia

1.

The beta-thalassemias are divided into β+-thalassemia, in which reduced levels of normal beta globin chains are produced, and β0-thalassemia, in which there is no beta globin chain synthesis.

2.

Hemoglobins are reported in order of quantity (e.g., HbF, HbS, HbA = HbF > HbS> HbA).

3.

Normal mean corpuscular volume: ≥70 fL at age six to 12 months; ≥72 fL at age one to two years; ≥81 fL in adults

4.

Interpretation can be difficult as coexisting iron deficiency and alpha-thalassemia are common in individuals with SCD and can also reduce the mean corpuscular volume.

5.

HbA2 results vary somewhat depending on laboratory method. The HbA2 percentages stated are not absolutes, and HbA2 percentage can be lower in individuals with Hb S/β0-thalassemia due to an HBB deletion.

From: Sickle Cell Disease

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