TABLE 2.

SCD: Neonatal Screening and Diagnostic Test Results

DisorderApproximate Percentage of US Patients With SCDNeonatal Screening Results*Hemoglobin Separation by Age 6 Weeks*Serial CBC and Reticulocyte CountsHematologic Studies by Age 2 Years
MCVHbA2 (%)HbF (%)
HbSS65FSFSHemolysis and anemia by age 6–12 moNormal or increased§<3.6§<25
HbSC25FSCFSCMild or no anemia by age 2 yNormal or decreasedNA<15
+-thalassemia8FSA or FSFSAMild or no anemia by age 2 yNormal or decreased>3.6<25
Sβ°-thalassemia2FSFSHemolysis and anemia by age 6–12 moDecreased>3.6<25
  • Table shows typical results—exceptions occur. Rare forms of SCD, such as SD-Punjab, SO-Arab, SC-Harlem, Sδβ-thalassemia, SE, and SLepore, not included.

  • * Hemoglobins reported in order of quantity (eg, FSA = F>S>A).

  • Normal or reference range of MCV is > 70 fL at age 6–12 mo; lower limits of reference range subsequently increase with age to 80 fL during adolescence.

  • HbA2 results vary somewhat depending on laboratory methodology.

  • § HbSS with coexistent α-thalassemia may show decreased MCV and HbA2 >3.6%; however, neonatal screening results from such infants usually show Bart’s hemoglobin.

  • NA = not applicable—quantity of HbA2 usually not measured in presence of HbC.

  • Quantity of HbA at birth is sometimes insufficient for detection.