Summary

 Background: Enumeration of T cell receptor excision circles (TREC) was recently adopted as a neonatal screening assay for severe combined immunodeficiency (SCID). Enumeration of kappa-deleting recombination excision circle (KREC) copy numbers can be similarly used for early assessment of B cell lymphopenia.

Objective: To assess the ability of TREC and KREC counts to identify patients with combined T and B cell immunodeficiency in a pilot study in Israel.

Methods: We studied seven children born in Israel during the years 2010–2011 and later diagnosed with SCID, and an additional patient with pure B cell immunodeficiency. TREC and KREC in peripheral blood upon diagnosis and in their neonatal Guthrie cards were analyzed using real-time quantitative polymerase chain reaction, as were Guthrie cards with dried blood spots from healthy newborns and from normal and SCID-like controls.

Results: The first features suggestive of SCID presented at age 3.1 ± 2.4 months in all patients. Yet, the diagnosis was made 4.1 ± 2.9 months later. Their TREC were undetectable or significantly low at their clinical diagnosis and in their originally stored Guthrie cards, irrespective of the amount of their circulating T cells. KREC were undetectable in six SCID patients who displayed B cell lymphopenia in addition to T cell lymphopenia. KREC were also undetectable in one patient with pure B cell immunodeficiency.

Conclusions: TREC and KREC quantification are useful screening tests for severe T and B cell immunodeficiency. Implementation of these tests is highly important especially in countries such as Israel where a high frequency of consanguinity is known to exist.