title: [A first pilot study on the neonatal screening of primary immunodeficiencies in Spain: TRECS and KRECS identify severe T- and B-cell lymphopenia].
abstract: BACKGROUND
  Early diagnosis of primary immunodeficiency such as severe combined immunodeficiency (SCID) and X-linked agammaglobulinemia (XLA) improves outcome of affected infants/children. The measurement of T-cell receptor excision circles (TRECS) and kappa-deleting recombination excision circles (KRECS) can identify neonates with severe T or B-cell lymphopenia.
  
  
  OBJECTIVE
  To determine TRECS and KRECS levels from prospectively collected dried blood spot samples (DBS) and to correctly identify severe T and B-cell lymphopenia.
  
  
  METHODS
  Determination of TRECS and KRECS by multiplex PCR from neonates born in two tertiary hospitals in Seville between February 2014 and May 2014. PCR cut-off levels: TRECS<15 copies/μl, KRECS<10 copies/μl, ACTB (β-actin)>1000 copies/μl. Internal (XLA, ataxia telangiectasia) and external (SCID) controls were included.
  
  
  RESULTS
  A total of 1068 out of 1088 neonates (mean GA 39 weeks (38-40) and BW 3238g (2930-3520) were enrolled in the study. Mean (median, min/max) copies/μl, were as follows: TRECS 145 (132, 8/503), KRECS 82 (71, 7/381), and ACTB 2838 (2763, 284/7710). Twenty samples (1.87%) were insufficient. Resampling was needed in one neonate (0.09%), subsequently giving a normal result. When using lower cut-offs (TRECS<8 and KRECS<4 copies/μl), all the samples tested were normal and the internal and external controls were correctly identified.
  
  
  CONCLUSIONS
  This is the first prospective pilot study in Spain using TRECS/KRECS/ACTB-assay, describing the experience and applicability of this method to identify severe lymphopenias. The ideal cut-off remains to be established in our population. Quality of sampling, storage and preparation need to be further improved.
authors.affiliation: Sección de Infectología e Inmunodeficiencias, Unidad de Pediatría, Hospital Virgen del Rocío, Sevilla, Instituto de Biomedicina de Sevilla (IBiS), Sevilla, España.
authors.forename: P
authors.initials: P
authors.lastname: Olbrich
authors.affiliation: Sección de Infectología e Inmunodeficiencias, Unidad de Pediatría, Hospital Virgen del Rocío, Sevilla, Instituto de Biomedicina de Sevilla (IBiS), Sevilla, España.
authors.forename: B
authors.initials: B
authors.lastname: de Felipe
authors.affiliation: Unidad de Metabolopatías, Hospital Universitario Virgen del Rocío, Sevilla, España.
authors.forename: C
authors.initials: C
authors.lastname: Delgado-Pecellin
authors.affiliation: Unidad de Neonatología, Hospital Universitario Virgen del Rocío, Sevilla, España.
authors.forename: R
authors.initials: R
authors.lastname: Rodero
authors.affiliation: Unidad de Neonatología, Hospital Universitario Virgen del Rocío, Sevilla, España.
authors.forename: P
authors.initials: P
authors.lastname: Rojas
authors.affiliation: Unidad de Neonatología, Hospital Universitario Virgen del Rocío, Sevilla, España.
authors.forename: J
authors.initials: J
authors.lastname: Aguayo
authors.affiliation: Unidad de Pediatría, Hospital Virgen del Valme, Sevilla, España.
authors.forename: J
authors.initials: J
authors.lastname: Marquez
authors.affiliation: Unidad de Pediatría, Hospital Virgen del Valme, Sevilla, España.
authors.forename: J
authors.initials: J
authors.lastname: Casanovas
authors.affiliation: Unidad de Inmunología, Hospital Universitario Virgen del Rocío, Sevilla, España.
authors.forename: B
authors.initials: B
authors.lastname: Sánchez
authors.affiliation: Unidad de Inmunología, Hospital Universitario Virgen del Rocío, Sevilla, España.
authors.forename: J M
authors.initials: JM
authors.lastname: Lucena
authors.affiliation: Grupo de Neurodesarrollo, Unidad de Pediatría, Hospital Virgen del Rocío, Sevilla, Instituto de Biomedicina de Sevilla (IBiS), Sevilla, España.
authors.forename: P
authors.initials: P
authors.lastname: Ybot-Gonzalez
authors.affiliation: Division of Clinical Immunology and Transfusion Medicine, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Estocolmo, Suecia; Translational Centre for Regenerative Medicine(TRM), University of Leipzig, Leipzig, Alemania; ImmunoDeficiencyCenter Leipzig at Hospital St Georg gGmbH Leipzig, Jeffrey Modell Diagnostic and Research Center for Primary Immunodeficiencies, Leipzig, Alemania.
authors.forename: S
authors.initials: S
authors.lastname: Borte
authors.affiliation: Sección de Infectología e Inmunodeficiencias, Unidad de Pediatría, Hospital Virgen del Rocío, Sevilla, Instituto de Biomedicina de Sevilla (IBiS), Sevilla, España. Electronic address: olafw.neth.sspa@juntadeandalucia.es.
authors.forename: O
authors.initials: O
authors.lastname: Neth
mesh_terms: D000361:Agammaglobulinemia / Q000097:blood / Q000175:diagnosis* / Q000235:genetics*; D000465:Algorithms; D001402:B-Lymphocytes; D004270:DNA, Circular / Q000097:blood; D040181:Genetic Diseases, X-Linked / Q000097:blood / Q000175:diagnosis* / Q000235:genetics*; D006801:Humans; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008231:Lymphopenia / Q000175:diagnosis*; D015997:Neonatal Screening / Q000379:methods*; D010865:Pilot Projects; D011446:Prospective Studies; D016511:Severe Combined Immunodeficiency / Q000097:blood / Q000175:diagnosis* / Q000235:genetics*; D012720:Severity of Illness Index; D013030:Spain; D013601:T-Lymphocytes
chemical_list: D004270:DNA, Circular
keywords: Agammaglobulinemia ligada al cromosoma C; Cribado neonatal; Inmunodeficiencia combinada grave; Inmunodeficiencias primarias; Linfopenia; Lymphopenia; Newborn screening; Primary immunodeficiency diseases; Severe combined immunodeficiency; X-linked agammaglobulinaemia