. Author manuscript; available in PMC: 2013 Mar 1.

Published in final edited form as: J Allergy Clin Immunol. 2012 Jan 29;129(3):607–616. doi: 10.1016/j.jaci.2012.01.032

Table 1. Test Methods Proposed to Screen for Severe Comlbined Immunodeficiency.

Analyte	Measurement	Platform	Uses dried blood spot	Comment
Lymphocytes	CBC and differential white blood count to determine lymphocyes/uL	Hospital clinical lab test on liquid cord blood or postnatal blood (heelstick or venous)	No	Costly, decentralized; false negatives for SCID with oligoclonal T cells, elevated B cells or maternal cells
Interleukin-7	IL-7 immuno-assay	ELISA or other method	Maybe	Stability, purification and assay problems; possible 2^nd tier test with TRECs
T cell proteins CD3, CD45	Immuno-assay for low CD3 (multiplex)	Automated fluorescent bead capture	Yes	Limited availability; false negatives for maternal or oligoclonal T cells; possible 2^nd tier test with TRECs
Mutation in SCID gene	DNA sequence determination	Custom resequencing array	Yes	False negatives; possible 2^nd tier test or future whole genome sequencing
T cell receptor excision circle	Copy number of circular DNA joints; comparison with control genomic DNA segment	Quantitative PCR on DNA	Yes	Biomarker for newly produced T cells; now used by several states; samples yielding poor DNA are inadequate