Quantification of κ-deleting recombination excision circles in Guthrie cards for the identification of early B-cell maturation defects.

Department of Pediatrics, National Defense Medical College, Saitama, Japan.
The Journal of allergy and clinical immunology (Impact Factor: 12.05). 03/2011; 128(1):223-225.e2. DOI: 10.1016/j.jaci.2011.01.052
Source: PubMed
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    ABSTRACT: Severe combined immunodeficiency (SCID) is the most severe form of inherited primary immunodeficiency and is a paediatric emergency. Delay in recognising and detecting SCID can have fatal consequences and also reduces the chances of a successful haematopoietic stem cell transplant (HSCT). Screening for SCID at birth would prevent children from dying before HSCT can be attempted and would increase the success of HSCT. There is strong evidence to show that SCID fulfills the internationally-established criteria for a condition to be screened for at birth. There is also a test (the T-cell receptor excision circle (TREC) assay) that is now being successfully used in an increasing number of US states to screen for SCID in routine newborn Guthrie samples. Concerted lobbying efforts have highlighted the need for newborn screening (NBS) for SCID, and its implementation is being discussed in Europe both at EU and individual country level, but as yet there is no global mandate to screen for this rare and frequently lethal condition. This paper summarizes the current evidence for, and the success of SCID NBS, together with a review of the practical aspects of SCID testing and the arguments in favour of adding SCID to the conditions screened for at birth.
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    ABSTRACT: Since its introduction as a public health programme in the United States in the early 1960s, newborn blood screening (NBS) has evolved from the detection of phenylalanine levels on filter paper to the application of DNA-based technologies to identify T-cell lymphopenia in infants with severe combined immunodeficiency. This latter use of NBS has required the development of an assay for T-cell lymphopenia based on the quantification of T-cell receptor excision circles (TRECs) that could be performed on dried blood spots routinely collected from newborn infants. The TREC-based NBS was developed six years ago, and there have already been 7 successful pilot studies since then. Similarly, efforts are now being made to establish a screen for B-cell defects, in particular agammaglobulinaemia, taking advantage of the introduction of the method for the quantification of K-deleting recombination excision circles (KRECs). A further achievement of NBS could be the simultaneous recognition of T- and B-cell defects using the combined quantification of TRECs and KRECs from Guthrie card blood spots. This approach may help the early identification of infants with T- and B-cell deficiencies so that they can then be referred to specialised paediatric centres, where a precise diagnosis of severe combined immunodeficiency and agammaglobulinaemia can be performed, and where then they can immediately receive specific therapy. Simultaneous TREC and KREC quantification should also allow classification of patients into subgroups and help identify children with less serious primary immunodeficiencies. This would help avoid the opportunistic infections and frequent hospitalisations that result from a late or lack of diagnosis.
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