Kim Malsam-Rysdon, Secretary of Health

SCID Newborn Screening - General Information

  • All South Dakota newborn screening (NBS) samples submitted to State Hygienic Lab (SHL) at the University of Iowa will have T-cell receptor excision circle (TREC) analysis run to screen for Severe Combined Immune Deficiencies (SCID). 


  • SCID is a lack of T cells which makes an infant extremely susceptible to infections. TRECs (T-cell receptor excision circles) are pieces of DNA produced in the thymus.


  • SCID newborn screening results will be reported out as MoM and TREC Cq. Cq stands for quantitation cycle. Both units are interchangeable. Cut offs include
    • TREC Cq: Soft [re-queue value] = 33.430; Hard [non-normal value] = 34.403; PP = 34.980
    • RNP Cq: > 26.000
    • MoM: Soft [re-queue value] > = 1.100; Hard [non-normal value] > = 1.132; PP > = 1.151


  • Factors affecting SCID newborn screening
    • Early Collection - A newborn screen is valid for SCID NBS testing even if baby is <24 hours of age.
    • Transfusions - Infants who have received a blood transfusion can have false positives (abnormally low TRECs). There is no change to our transfusion protocol for SCID screening.
    • TREC results are not affected by TPN use
    • TREC results are not affected by NPO status
    • TREC results are not affected by the mother’s immune system
    • TREC results could be affected if drawn from a heparinized line
    • Premature infants frequently have lower TREC levels compared to term infants. This finding can be secondary to several factors including time for T-cell maturation in the thymus, medications given prior to delivery which might reduce T-cell numbers, and/or dilutional factors related to sample collection from an indwelling catheter. 


  • Clinical information indicating infant is at high risk for SCID would include
    • Family history of primary immunodeficiency disorder
    • Early childhood deaths in the family
    • Symptoms of possible underlying infection (fever, poor intake, lethargy, failure to gain weight and persistent diarrhea)
    • Physical features such as skin rash, oral ulcers, enlarged spleen, enlarged liver, midline defects or coarse facial features



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