Health Professionals Guide to Newborn Screening

Severe Combined Immune Deficiency (SCID)

Severe Combined Immune Deficiency (SCID) is a group of inherited diseases that result in a lack of T-cells and severely reduced B-cell function. The mode of inheritance may be X-linked or autosomal recessive. Babies with SCID are extremely susceptible to infection and die early in life unless treated with allogeneic bone marrow transplantation.

Prevalence (WI):	1:70,000
Analyte Measured:	T-Cell Receptor Excision Circles (TRECs)   NOTE: TRECs result from the productive rearrangement of the T-cell receptor gene and are found in normal naïve t-cells, which are consistently absent/low in all SCID babies.  TRECs may also be low in other primary or secondary immunodeficiencies.  Therefore, confirmatory testing by flow cytometry is necessary for the diagnosis of SCID.
Abnormal Levels:	< 25 TRECs/µ/L
Feeding Effect:	None
Timing Effect:	< 24 hours of age: Repeat at two weeks ³ 24 hours of age: Results are valid
Confirmation:	Flow cytometry measuring the absolute number of T-cells , B-cells, and NK cells.
Treatment:	Allogenic bone marrow (stem cell) transplantation.  Prophylactic antibiotics, antiviral and antifungal agents, and intravenous gamma globulin are given until bone marrow transplantation is performed.

COMMENT: Since the diagnosis of SCID can be difficult, it is recommended that one of the states pediatric immunology specialists be consulted for proper follow up when abnormal results are reported from the screening laboratory. A list of specialists is provided on the written report issued by the newborn screening laboratory.

Information on treatment centers is also available on this site.

For information about other screened disorders, click on the next page button, or follow one of these links:

• Argininosuccinic Acidemia (ASA)	• Hemoglobin Variants
• Biotinidase Deficiency	• Homocystinuria
• Congenital Adrenal Hyperplasia	• Hypermethioninemia
• Congenital Hypothyroidism	• Hyperphenyalaninemia
• Citrullinemia (Types I & II)	• Maple Syrup Urine Disease
• Cystic Fibrosis	• Organic Acidemias (14)
• Fatty Acid Oxidation Disorders (12)	• Phenylketonuria (Includes Biopterin Cofactor defects of regeneration and biosynthesis)
• Galactosemia	• Severe Combined Immune Deficiency (SCID)
• Hemoglobin S-Beta Thallassemia	• Sickle Cell Disease
• Hemoglobin S/C Disease	• Tyrosinemia (Types I,II, & III)

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