Brief Description

Severe combined immunodeficiency (SCID) is a disorder where a child is born without a functioning immune system and therefore lacks the ability to fight off infections. Without early detection and intervention, babies with SCID will suffer multiple infections and typically die before their first birthday. SCID includes a group of rare but serious and potentially fatal, inherited immune disorders in which T-lymphocytes fail to develop, and B-lymphocytes are either absent or decreased. Infections are usually serious. Untreated patients develop life-threatening infections due to bacteria, viruses, and fungi with average age at the onset of symptoms at 2 months. Typically, infants with SCID will die from infection by one year of age unless the infant's immune system is restored through treatment. Early detection through newborn screening and treatment can result in markedly improved survival rates.

Quick Facts

Laboratory Unit

Methodology

TREC Real-Time PCR Assay

Specimen Collection

Missouri newborn screening samples must only be collected on the FDA approved blood collection forms that are provided by the State Public Health Laboratory and must be pre-purchased at a cost of $85 per collection form. The optimum collection time is between 24 and 48 hours-of-age. The instructions for collecting the samples are listed on the back of the collection form. All 5 circles on the filter paper need to be filled with blood from one side and then air dried for at least 3 hours in a horizontal position without allowing the blood to touch any surface during drying, including other parts of the card (see image). 
See "Rules for Collection".

Storage/Transport

Store the dried blood samples at room temperature in the envelopes provided by the State Public Health Laboratory and transport within 24 hours of collection

Acceptable Specimen Type(s)

Initial Screen (the red form) or Repeat Screen (the green form)

Test Request Form(s)

Included in kit

Possible Results

Normal: No action required.
Borderline Risk: Results are in the borderline risk range. Repeat the newborn screen is necessary.
High Risk: Results are in the high risk range. Final results are immediately sent to the Newborn Screening SCID coordinator. The SCID coordinator will contact the primary care provider immediately and provide instructions for follow up, along with the SCID results. It is important that the primary care provider follow the instructions and contact the pediatric immunologist for appropriate follow up testing and consultation.
No Results: Results for SCID were inconclusive. Please send a repeat newborn screening specimen as soon as possible, preferably no later than 1 week.
All final results are sent to the submitter and physcian of record/primary care provider. 

Reference Range

CT < 36.0 Normal
Description of Ct values: In a real time PCR assay, a positive reaction is detected by accumulation of a fluorescent signal. The Ct (cycle threshold) is defined as the number of cycles required for the fluorescent signal to cross the threshold. The point at which the fluorescent signal intersects the threshold line is the Ct value and it tells you the number of cycles required to detect a real signal of fluorescence from a sample. In this assay, it is a relative measure of the concentration of T-Cell Receptor Excision Circles (TREC) in each blood spot sample. The Ct value is inversely proportional to the amount of target nucleic acid in the sample, so Ct increases with a decreasing amount of target. Keep in mind that Ct values from PCR reactions run under different conditions, in different laboratories, or with different reagents cannot be directly compared.

Unacceptable Conditions

Interfering Substances

SCID results may not be as reliable in infants who are premature, sick, and/or transfused. A repeat newborn screen will be necessary. Follow the Missouri NICU guidelines.
Screening for SCID is not appropriate for SCID/Primary T-Cell lymphopenia in children older than 1 year of age. A "No result" will be given. If the child's clinical presentation could be due to SCID/Primary T-Cell lymphopenia, clinical evaluation is recommended.

Result Reported

1 to 3 working days after receipt of specimen

Fees

$85 charge - for full panel of screening disorders 

CPT Codes

81479

LOINC/SNOMED Codes

N/A

Additional Information

Estimated prevalence is between 1:40,000 and 1:75,000