Implementation of second-tier tests in newborn screening for the detection of vitamin B12 related acquired and genetic disorders: results on 258,637 newborns

Homocisteïna; Cribratge de nounats; Deficiència de vitamina B12Homocisteína; Cribado de recién nacidos; Deficiencia de vitamina B12Homocysteine; Newborn screening; Vitamin B12 deficiencyBackground Alteration of vitamin B12 metabolism can be genetic or acquired, and can result in anemia, failure to thrive, developmental regression and even irreversible neurologic damage. Therefore, early diagnosis and intervention is critical. Most of the neonatal cases with acquired vitamin B12 deficiency have been detected by clinical symptoms and only few of them trough NBS programs. We aim to assess the usefulness of the second-tier test: methylmalonic acid (MMA), methylcitric acid (MCA) and homocysteine (Hcys) in our newborn screening program and explore the implications on the detection of cobalamin (vitamin B12) related disorders, both genetic and acquired conditions. Methods A screening strategy using the usual primary markers followed by the analysis of MMA, MCA and Hcys as second tier-test in the first dried blood spot (DBS) was developed and evaluated. Results During the period 2015–2018 a total of 258,637 newborns were screened resulting in 130 newborns with acquired vitamin B12 deficiency (incidence 1:1989), 19 with genetic disorders (incidence 1:13,613) and 13 were false positive. No false negatives were notified. Concerning the second-tier test, the percentage of cases with MMA above the cut-off levels, both for genetic and acquired conditions was very similar (58% and 60%, respectively). Interestingly, the percentage of cases with increased levels of Hcys was higher in acquired conditions than in genetic disorders (87% and 47%, respectively). In contrast, MCA was high only in 5% of the acquired conditions versus in 53% of the genetic disorders, and it was always very high in all patients with propionic acidemia. Conclusions When screening for methylmalonic acidemia and homocystinuria, differential diagnosis with acquired vitamin B12 deficiency should be done. The results of our strategy support the inclusion of this acquired condition in the NBS programs, as it is easily detectable and allows the adoption of corrective measures to avoid the consequences of its deficiency

Newborn Screening for SCID: Experience in Spain (Catalonia)

Linfocitos T; Cribado de recién nacidos; Inmunodeficiencia combinada severaLimfòcits T; Cribratge de nounats; Immunodeficiència combinada severaT-lymphocytes; Newborn screening; Severe combined immunodeficiencyNewborn screening (NBS) for severe combined immunodeficiency (SCID) started in Catalonia in January-2017, being the first Spanish and European region to universally include this testing. In Spain, a pilot study with 5000 samples was carried out in Seville in 2014; also, a research project with about 35,000 newborns will be carried out in 2021–2022 in the NBS laboratory of Eastern Andalusia. At present, the inclusion of SCID is being evaluated in Spain. The results obtained in the first three and a half years of experience in Catalonia are presented here. All babies born between January-2017 and June-2020 were screened through TREC-quantification in DBS with the Enlite Neonatal TREC-kit from PerkinElmer. A total of 222,857 newborns were screened, of which 48 tested positive. During the study period, three patients were diagnosed with SCID: an incidence of 1 in 74,187 newborns; 17 patients had clinically significant T-cell lymphopenia (non-SCID) with an incidence of 1 in 13,109 newborns who also benefited from the NBS program. The results obtained provide further evidence of the benefits of early diagnosis and curative treatment to justify the inclusion of this disease in NBS programs. A national NBS program is needed, also to define the exact SCID incidence in Spain

Inter-rater reliability assessment for the new-born screening quality assurance

IntroductionTo ensure the quality of the new-born screening (NBS), our laboratory reviewed the analytical procedure to detect subjective steps that may represent a risk to the patient. Two subjective activities were identified in the extra-analytical phases: the classification of dried blood spots (DBS) according to their quality and the assignment of haemoglobin patterns. To keep these activities under control, inter-rater studies were implemented. This study aimed to evaluate the inter-rater reliability and the effectiveness of the measures taken to improve the agreement between observers, to assure NBS results’ quality. Materials and methodsDried blood spots specimens were used for the inter-rater studies. Ten studies were performed to assess DBS quality classification, and four to assess the assignment of haemoglobin patterns. Krippendorff’s alpha test was used to estimate inter-rater reliability. Causes were investigated when alpha values were below 0.80. ResultsFor both activities, the reliability obtained in the first studies was inadequate. After investigation, we detected that the criterion to classify a DBS as scant was not consolidated, and also a lack of consensus on whether or not to report Bart’s haemoglobin depending on its percentage. Alpha estimates became higher once the training was reinforced and a consensus about the appropriate criteria to be applied was reached. ConclusionInter-rater reliability assessment helped us to ensure the quality of subjective activities that could add variability to NBS results. Furthermore, the evolution of the alpha value over time allowed us to verify the effectiveness of the measures adopted

First universal newborn screening program for severe combined immunodeficiency in Europe: two-years' experience in Catalonia (Spain)

Newborn screening; Severe combined immunodeficiency; T-cell receptor excision circlesCribratge de nadons; Immunodeficiència combinada greu; Cercles d'excisió de receptors de cèl·lules TCribado de recién nacidos; Inmunodeficiencia combinada grave; Círculos de escisión de receptores de células TSevere combined immunodeficiency (SCID), the most severe form of T-cell immunodeficiency, can be screened at birth by quantifying T-cell receptor excision circles (TRECs) in dried blood spot (DBS) samples. Early detection of this condition speeds up the establishment of appropriate treatment and increases the patient's life expectancy. Newborn screening for SCID started in January 2017 in Catalonia, the first Spanish and European region to universally include this testing. The results obtained in the first 2 years of experience are evaluated here. All babies born between January 2017 and December 2018 were screened. TREC quantification in DBS (1.5 mm diameter) was performed with the Enlite Neonatal TREC kit from PerkinElmer (Turku, Finland). In 2018, the retest cutoff in the detection algorithm was updated based on the experience gained in the first year, and changed from 34 to 24 copies/μL. This decreased the retest rate from 3.34 to 1.4% (global retest rate, 2.4%), with a requested second sample rate of 0.23% and a positive detection rate of 0.02%. Lymphocyte phenotype (T, B, NK populations), expression of CD45RA/RO isoforms, percentage and intensity of TCR αβ and TCR γδ, presence of HLA-DR+ T lymphocytes, and in vitro lymphocyte proliferation were studied in all patients by flow cytometry. Of 130,903 newborns screened, 30 tested positive, 15 of which were male. During the study period, one patient was diagnosed with SCID: incidence, 1 in 130,903 births in Catalonia. Thirteen patients had clinically significant T-cell lymphopenia (non-SCID) with an incidence of 1 in 10,069 newborns (43% of positive detections). Nine patients were considered false-positive cases because of an initially normal lymphocyte count with normalization of TRECs between 3 and 6 months of life, four infants had transient lymphopenia due to an initially low lymphocyte count with recovery in the following months, and three patients are still under study. The results obtained provide further evidence of the benefits of including this disease in newborn screening programs. Longer follow-up is needed to define the exact incidence of SCID in Catalonia

BCKDK deficiency: a treatable neurodevelopmental disease amenable to newborn screening

There are few causes of treatable neurodevelopmental diseases described to date. Branched-chain ketoacid dehydrogenase kinase (BCKDK) deficiency causes branched-chain amino acid (BCAA) depletion and is linked to a neurodevelopmental disorder characterized by autism, intellectual disability and microcephaly. We report the largest cohort of patients studied, broadening the phenotypic and genotypic spectrum. Moreover, this is the first study to present newborn screening findings and mid-term clinical outcome. In this cross-sectional study, patients with a diagnosis of BCKDK deficiency were recruited via investigators’ practices through a MetabERN initiative. Clinical, biochemical and genetic data were collected. Dried blood spot (DBS) newborn screening (NBS) amino acid profiles were retrieved from collaborating centres and compared to a healthy newborn reference population. Twenty-one patients with BCKDK mutations were included from 13 families. Patients were diagnosed between 8 months and 16 years (mean: 5.8 years, 43% female). At diagnosis, BCAA levels (leucine, valine and isoleucine) were below reference values in plasma and in CSF. All patients had global neurodevelopmental delay; 18/21 had gross motor function (GMF) impairment with GMF III or worse in 5/18, 16/16 intellectual disability, 17/17 language impairment, 12/17 autism spectrum disorder, 9/21 epilepsy, 12/15 clumsiness, 3/21 had sensorineural hearing loss and 4/20 feeding difficulties. No microcephaly was observed at birth, but 17/20 developed microcephaly during follow-up. Regression was reported in six patients. Movement disorder was observed in 3/21 patients: hyperkinetic movements (1), truncal ataxia (1) and dystonia (2). After treatment with a high-protein diet (≥ 2 g/kg/day) and BCAA supplementation (100–250 mg/kg/day), plasma BCAA increased significantly (P < 0.001), motor functions and head circumference stabilized/ improved in 13/13 and in 11/15 patients, respectively. Among cases with follow-up data, none of the three patients starting treatment before 2 years of age developed autism at follow-up. The patient with the earliest age of treatment initiation (8 months) showed normal development at 3 years of age. NBS in DBS identified BCAA levels significantly lower than those of the normal population. This work highlights the potential benefits of dietetic treatment, in particular early introduction of BCAA. Therefore, it is of utmost importance to increase awareness about this treatable disease and consider it as a candidate for early detection by NBS programmes.A.G.C. is supported by FIS P118/00111, FI21/0073 ‘Instituto de Salud Carlos III (ISCIII)’ and ‘Fondo Europeo de desarrollo regional (FEDER)’

Estudios de biomarcadores y de posibles terapias en la deficiencia del transportador de creatina y en la enfermedad de Niemann-Pick tipo C

[spa] En esta tesis se estudian dos aspectos, el desarrollo de herramientas diagnósticas y terapéuticas aplicado a dos enfermedades metabólicas hereditarias: la deficiencia del transportador de creatina (CRTR) y la enfermedad de Niemann-Pick tipo C (NPC). La deficiencia de CRTR, cuya herencia se halla ligada al cromosoma X, se caracteriza por afectación neurológica, retraso en el lenguaje y comportamiento autista, debido a la disminución en el contenido celular de creatina (Cr). La terapia con Cr exógena resulta ineficaz, sin embargo, recientemente, estudios en modelos animales han demostrado la eficacia de algunos derivados de Cr (fosfocreatina-Mg-complex (PCr-Mg-CPLX) y creatina-benzil-éster (CrOBzl)). En esta tesis se ha estudiado la eficacia de estos compuestos en fibroblastos de pacientes con deficiencia de CRTR, iPS generadas a partir de fibroblastos de pacientes, y en células HUVEC y HBMEC silenciadas con siRNA como modelos de endotelio vascular y de barrera hematoencefálica. Desafortunadamente nuestros resultados mostraron que el tratamiento con PCr-MG-CPLX, CrOBzl y nanopartículas de oro (Au-HC-NPs) no incrementaban el contenido intracelular de Cr, por lo que no serían tratamientos eficaces para la deficiencia de CRTR. También se estudió la eficacia del tratamiento con precursores de Cr, arginina y glicina. Sin embargo, no se observó ninguna mejoría en la síntesis endógena de Cr, por lo que no se consideraría una buena estrategia terapéutica. Estos resultados han proporcionado conocimientos acerca de la estabilidad y permeabilidad de estos compuestos; de modo que se ha evidenciado que es necesario mejorar y modificar el diseño de los mismos con el fin de obtener compuestos más estables y lipófilos, capaces de atravesar la barrera hematoencefálica, para que puedan ser eficaces en la terapia de esta enfermedad. Por otro lado, se evaluó el papel del sistema Cr/CrP/CK/ATP en conjunto como biomarcador de las deficiencias cerebrales de creatina (CCDS), ya que previamente se habían descrito niveles disminuidos de CK en 1 paciente con deficiencia de CRTR y en un paciente con deficiencia de guanidinoacetato metiltransferasa (GAMT). En este trabajo en primer lugar conseguimos obtener un método sensible y robusto mediante HPLC-ESI-MS/MS para el análisis conjunto de ATP, ADP, AMP, Cr, y CrP. El estudio de pacientes con CCDS en plasma mostró niveles bajos de CK en 2 pacientes con deficiencia de CRTR y 1 paciente con deficiencia de GAMT. Sin embargo, en fibroblastos no se observaron diferencias en la actividad CK comparado con los controles. En fibroblastos de los 9 pacientes los niveles de ATP y ADP estaban elevados, y los de Cr y CrP estaban disminuidos. Este es el primer estudio, en el que se analiza en conjunto cada uno de los marcadores involucrados en el sistema energético de la Cr en pacientes con CCDS. Este trabajo corrobora que la actividad CK plasmática podría ser un buen biomarcador de las CCDS y se sugiere que el análisis de cada uno de estos metabolitos podría ser una herramienta útil para la valoración de la respuesta a tratamientos. Previamente también se había descrito que pacientes con enfermedades mitocondriales tenían niveles elevados de Cr, sugiriendo su papel como biomarcador. Dada esta evidencia, hemos estudiado 33 pacientes con enfermedades mitocondriales y se ha observado un aumento notable de Cr en 9 pacientes. La Cr tiene una baja sensibilidad (60%) y una especificidad aceptable (83%) en estas enfermedades. De este estudio se deduce que la Cr, junto con la alteración de otros parámetros debería tenerse en cuenta en la evaluación de una sospecha mitocondrial. Respecto a la enfermedad de NPC, de herencia autosómica recesiva, ésta se caracteriza por neurodegeneración causada por un trastorno en el transporte lisosomal del colesterol libre. El diagnóstico bioquímico convencional se basa en la tinción con filipina de los acúmulos de colesterol libre en fibroblastos. No obstante, esta técnica presenta baja sensibilidad en los pacientes de presentación adulta o con fenotipo bioquímico variante; además de ser una técnica invasiva que implica la obtención de una biopsia de piel y el posterior cultivo de fibroblastos, lo que conduce a largo período de tiempo hasta obtener el diagnóstico. Debido a estas limitaciones surge la necesidad de encontrar biomarcadores rápidos y fiables que ayuden al diagnóstico de la enfermedad. Al inicio de esta tesis se describió el aumento en plasma de dos oxiesteroles, colestano-3β,5α,6β-triol (CT) y 7-cetocolesterol (7-KC), en pacientes NPC sugiriendo su papel como biomarcadores. En este trabajo se ha conseguido obtener un método sensible mediante HPLC-ESI-MS/MS para el análisis de CT y 7-KC capaz de discriminar entre pacientes y sujetos sanos. Se ha analizado por primera vez, el papel de estos oxiesteroles en una cohorte de 16 pacientes NPC diagnosticados en el territorio español y se ha observado que efectivamente tenían niveles elevados de CT y 7-KC, además de correlacionarse perfectamente con el fenotipo clínico. También hemos estudiado 2 pacientes con fenotipo bioquímico variante y un paciente asintomático y en todos CT y 7-KC se encontraban elevados. Para conocer la especificidad de estos biomarcadores estudiamos distintos grupos de enfermedades y se observó que CT estaba también incrementado en pacientes con deficiencia de lipasa ácida lisosomal, Niemann-Pick tipo B y Xantomatosis cerebrotendinosa; 7-KC se encontró elevado en varios grupos de enfermedades. Por ello, CT y 7-KC no son específicos de la enfermedad de NPC aunque sí sensibles, de modo que se ha incluido esta estrategia en la primera línea diagnóstica de la enfermedad de NPC en nuestro laboratorio asistencial. Con esta inclusión, esperamos identificar nuevos pacientes, no sólo de NPC, sino también de otras enfermedades como XCT, deficiencia de LAL, o NPA/NPB

Impacto de la inclusión de pruebas de segundo nivel en el programa de cribado neonatal de Cataluña y en otros programas internacionales

Background: Newborn screening programmes (NBSP) have experienced a qualitative breakthrough due to the implementation of tandem mass spectrometry. However, the tests used give rise to false positives (FP) generating an excessive request for second samples with the consequent anxiety of the families. In order to avoid this problem several programmes have developed second-tier tests (2TT). Methods: This article presents our experience in the implementation of 2TT in the NBSP of Catalonia, as well as in other international programmes. Results: From 2004 to the present, 2TT tests have been developed for more than 30 diseases. The use of 2TT helps to decrease the FP rate and increase the positive predictive value (PPV). In the NBSP of Catalonia, the implementation of 2TT for the detection of methylmalonic and propionic acidemias, homocystinurias, maple syrup disease and citrulinaemia, has managed to increase the PPV to 95% and decrease the PF rate to less than 0.01%. In cystic fibrosis, the application of 2TT slightly increases PPV but with a significant decrease in the request for second samples and in the number of cases referred to clinical units. Conclusions: The introduction of 2TT in the NBSP allows to reduce considerably the FP, decreases the number of requested samples, as well as both anxiety and stress of the families, at the same time that the hospital costs are reduced and the PPV is increased, improving notably the efficiency of the NBSP.Fundamentos: Los programas de cribado neonatal (PCN) han experimentado un gran avance cualitativo debido a la implementación de la espectrometría de masas en tándem. Sin embargo, las pruebas utilizadas dan lugar a falsos positivos (FP) generando una excesiva solicitud de segundas muestras con la consiguiente ansiedad de las familias. Con el fin de evitar este problema diversos programas han desarrollado pruebas de segundo nivel (2TT). Métodos: En este artículo se presenta nuestra experiencia en la implementación de 2TT en el PCN de Cataluña, así como en otros programas internacionales. Resultados: Desde el año 2004 hasta la actualidad se han desarrollado pruebas de 2TT para más de 30 enfermedades. La utilización de 2TT ayuda a disminuir la tasa de FP y aumentar el valor predictivo positivo (VPP). En el PCN de Cataluña, la implementación de 2TT para la detección de acidemias metilmalónicas y propiónica, homocistinurias, jarabe de arce y citrulinemia, ha conseguido aumentar el VPP a un 95% y disminuir la tasa de FP a menos del 0,01%. En la fibrosis quística la aplicación de 2TT aumenta ligeramente el VPP pero con disminución significativa de la solicitud de segundas muestras y de los casos referidos a las unidades clínicas. Conclusiones: La introducción de los 2TT en los PCN permite reducir considerablemente los FP, disminuye el número de muestras solicitadas, así como la ansiedad y el estrés de las familias, a la vez que se reducen los costes hospitalarios y se aumenta el VPP, mejorando notablemente la eficiencia de los PCN

Respuesta del laboratorio de cribado neonatal de Cataluña ante la pandemia por SARS-CoV-2

Faced with the prospect of a collapsed health system due to the COVID-19 pandemic, the professionals involved in the Neonatal Screening Programme (NSP) of Catalonia had to adapt to this situation in a flexible, forceful and efficient manner. The most important goals were to prevent the risk of infection in the professionals, in families and their newborns, as well as to ensure the same effectiveness for the early detection of the diseases included in our programme. To this end, the laboratory was reorganised by dividing the staff into groups and the spaces were redistributed. It was also necessary to modify several protocols and circuits, especially for the management of early discharges from maternity centres, and for the collection of the necessary second samples (from newborns with inconclusive results or for low quality samples). In general, a 36% reduction in the time of arrival of these second samples at the laboratory was achieved with respect to the previous circuit. In the specific case of cystic fibrosis detection, the implementation of a new strategy meant a 100% reduction in the request for second samples and a 70% reduction in the age of diagnosis of the newborn. After evaluating these changes, it can be concluded that in the face of the pandemic, the NSP of Catalonia showed determined leadership, aligning all its professionals, ensuring the continuity of the activity in the programme and generating new opportunities. The new processes and circuits implemented have been definitively consolidated, improving the efficiency of the programme.Ante la crisis de un sistema sanitario colapsado debido a la pandemia por la COVID-19, los profesionales implicados en el Programa de Cribado Neonatal (PCN) de Cataluña nos tuvimos que adaptar a dicha situación de forma ágil, contundente y eficiente. Los objetivos prioritarios fueron prevenir el riesgo de contagio tanto en los profesionales sanitarios como en las familias y sus recién nacidos, así como asegurar la misma eficacia para la detección precoz de las enfermedades incluidas en el PCN. Para ello, se reorganizó el laboratorio dividiendo en grupos al personal y se redistribuyeron los espacios. También fue necesario modificar varios protocolos y circuitos, en especial para la gestión de las altas precoces de los centros maternales y para la toma de las segundas muestras necesarias (de recién nacidos que presentaron resultados dudosos o por muestra inválida). En general, se consiguió una reducción del 36% del tiempo de llegada de estas segundas muestras al laboratorio respecto al circuito anterior. Para la detección de la fibrosis quística, la implementación de una nueva estrategia supuso una reducción del 100% en la solicitud de segundas muestras y del 70% en la edad de diagnóstico del recién nacido. Tras la evaluación de estos cambios, se puede concluir que ante la pandemia el PCN de Cataluña mostró un liderazgo decidido, alineando a todos sus profesionales, asegurando la continuidad de la actividad en el programa y generando nuevas oportunidades. Los nuevos procesos y circuitos de trabajo implantados han quedado definitivamente consolidados, mejorando la eficiencia del programa

First universal newborn screening program for severe combined immunodeficiency in Europe: two-years' experience in Catalonia (Spain)

Newborn screening; Severe combined immunodeficiency; T-cell receptor excision circlesCribratge de nadons; Immunodeficiència combinada greu; Cercles d'excisió de receptors de cèl·lules TCribado de recién nacidos; Inmunodeficiencia combinada grave; Círculos de escisión de receptores de células TSevere combined immunodeficiency (SCID), the most severe form of T-cell immunodeficiency, can be screened at birth by quantifying T-cell receptor excision circles (TRECs) in dried blood spot (DBS) samples. Early detection of this condition speeds up the establishment of appropriate treatment and increases the patient's life expectancy. Newborn screening for SCID started in January 2017 in Catalonia, the first Spanish and European region to universally include this testing. The results obtained in the first 2 years of experience are evaluated here. All babies born between January 2017 and December 2018 were screened. TREC quantification in DBS (1.5 mm diameter) was performed with the Enlite Neonatal TREC kit from PerkinElmer (Turku, Finland). In 2018, the retest cutoff in the detection algorithm was updated based on the experience gained in the first year, and changed from 34 to 24 copies/μL. This decreased the retest rate from 3.34 to 1.4% (global retest rate, 2.4%), with a requested second sample rate of 0.23% and a positive detection rate of 0.02%. Lymphocyte phenotype (T, B, NK populations), expression of CD45RA/RO isoforms, percentage and intensity of TCR αβ and TCR γδ, presence of HLA-DR+ T lymphocytes, and in vitro lymphocyte proliferation were studied in all patients by flow cytometry. Of 130,903 newborns screened, 30 tested positive, 15 of which were male. During the study period, one patient was diagnosed with SCID: incidence, 1 in 130,903 births in Catalonia. Thirteen patients had clinically significant T-cell lymphopenia (non-SCID) with an incidence of 1 in 10,069 newborns (43% of positive detections). Nine patients were considered false-positive cases because of an initially normal lymphocyte count with normalization of TRECs between 3 and 6 months of life, four infants had transient lymphopenia due to an initially low lymphocyte count with recovery in the following months, and three patients are still under study. The results obtained provide further evidence of the benefits of including this disease in newborn screening programs. Longer follow-up is needed to define the exact incidence of SCID in Catalonia

Primer programa europeo de cribado neonatal para la inmunodeficiencia combinada grave: experiencia de tres años en Cataluña

Severe combined immunodeficiency (SCID), the most severe form of T-cell immunodeficiency, can be screened at birth by quantifying T-cell receptor excision circles (TREC) in dried blood spot (DBS) samples. Early detection of this condition speeds up the establishment of appropriate treatment and increases the patient’s life expectancy. Newborn screening for SCID started in January 2017 in Catalonia, the first Spanish and European region to universally include this testing. The results obtained in the first three years and a half of experience (January 2017 – June 2020) are shown here, using EnLite Neonatal TREC kit (Perkin Elmer) with 20 copies/μL as TREC detection cutoff. Of 222,857 newborns screened, 48 tested positive: three patients were diagnosed with SCID (incidence 1:74,285); 17 patients had clinically significant T-cell lymphopenia (non-SCID) with an incidence of 1 in 13,109 newborns; twenty two patients were considered false-positive cases because of an initially normal lymphocyte count with normalization of TREC between 3 and 6 months of life; one case had transient lymphopenia due to an initially low lymphocyte count with recovery in the following months; and five patients are still under study. The results obtained provide further evidence of the benefits of including this disease in newborn screening programs. Even longer follow-up could be necessary to define the exact incidence of SCID in Catalonia.La inmunodeficiencia combinada grave (IDCG) es la forma más grave de inmunodeficiencia primaria, que afecta sobre todo a los linfocitos T, y puede ser detectada al nacer mediante la cuantificación de los círculos de escisión del receptor de linfocitos T (TREC) en una muestra de sangre impregnada en papel (DBS). La detección precoz de esta enfermedad permite establecer de forma temprana un tratamiento adecuado en el paciente, permitiendo así su curación. El cribado neonatal de IDCG comenzó en Cataluña en enero de 2017, siendo la primera región española y europea en incluirla oficial y universalmente en su programa. En el presente trabajo se presentan los resultados obtenidos durante los tres primeros años y medio de experiencia (enero 2017 – junio 2020) empleando el kit EnLite Neonatal TREC (Perkin Elmer), con un cutoff de detección de TREC de 20 copias/μL. De 222.857 recién nacidos analizados, cuarenta y ocho fueron detecciones positivas: tres casos de IDCG (incidencia de 1:74.285); diecisiete casos de linfopenia T no IDCG (incidencia de 1:13.109); veintidós casos falsos positivos (recuento de linfocitos inicialmente normal, con normalización de TREC entre los tres y seis meses de vida); un caso con linfopenia transitoria (con un recuento de linfocitos inicialmente bajo, que se normaliza en los meses siguientes); y cinco pacientes se encuentran todavía en estudio. Los resultados obtenidos aportan evidencias de los beneficios que supone incluir esta enfermedad en los programas de cribado neonatal. Podría ser necesario un seguimiento todavía más prolongado para acabar de definir la incidencia exacta de IDCG en Cataluña