What to Do with an Abnormal Newborn Screen for Severe Combined Immune Deficiency

Efficient screening strategies for severe combined immunodeficiencies in newborns

INTRODUCTION

Severe combined immunodeficiency (SCID) is one of the most severe forms of inborn errors of immunity (IEI), affecting both cellular and humoral immunity. Without curative treatment such as hematopoietic stem cell transplantation or gene therapy, affected infants die within the first year of life. Due to the severity of the disease, asymptomatic status early in life, and improved survival in the absence of pretransplant infections, SCID was considered a suitable candidate for newborn screening (NBS).

AREAS COVERED

Many countries have introduced SCID screening based on T-cell receptor excision circle (TREC) detection in their NBS programs. Screening an entire population is a radical departure from previous paradigms in the field of immunology. Efficient screening strategies are cost-efficient and balance high sensitivity while preventing high numbers of referrals. NBS for SCID is accompanied by (actionable) secondary findings, but many NBS programs have optimized their screening strategy by adjusting algorithms or including second-tier tests. Harmonization of screening terminology is of great importance for international shared learning.

EXPERT OPINION

The expansion of NBS is driven by the development of new test modalities and treatment options. In the near future, other techniques such as next-generation sequencing will pave the way for NBS of other IEI. Exciting times await for population-based screening programs.

Trends in Pediatric Primary Immunodeficiency: Incidence, Utilization, Transplantation, and Mortality

BACKGROUND

Primary immunodeficiency disorders (PIDDs) describe a myriad of diseases caused by inherited defects within the immune system. As the number of identified genetic defects associated with PIDDs increases, understanding the incidence and outcomes of PIDD patients becomes imperative.

OBJECTIVE

To characterize the frequency of new diagnoses, patterns of health care utilization, rates of hematopoietic stem cell transplantation (HSCT), and mortality in pediatric patients with PIDDs.

METHODS

A retrospective cohort analysis of the Pediatric Health Information System database from 2004 to 2018 for pediatric inpatients with an International Classification of Diseases, Ninth and 10th Revisions (ICD-9/ICD-10). code associated with PIDD.

RESULTS

A total of 17,234 patients with a PIDD were hospitalized from 2004 to 2018. There were 2.8 new PIDD diagnoses and 6.3 PIDD hospitalizations per 1,000 discharges; these metrics were unchanged during the study period. The number of new diagnoses for B-cell and antibody defects significantly increased over time. The number of new PIDD diagnoses significantly increased in adolescents or adults and decreased in infants. T-cell disorders had the highest number of intensive care unit admissions. There were 747 PIDD patients who underwent HSCT; complications of HSCT significantly decreased over time. Mortality rates significantly decreased in all PIDD patients and in patients receiving HSCT.

CONCLUSIONS

The total hospitalizations and incidence of PIDDs within the hospitalized pediatric population were unchanged. There were significant changes in the class of PIDD diagnosed, the age at diagnosis, and health care utilization metrics. Mortality significantly decreased over time within the PIDD cohort.

Retrospective Analysis of a New York Newborn Screen Severe Combined Immunodeficiency Referral Center

In 2010, the New York State (NYS) Newborn Screen (NBS) Program added the T cell receptor excision circle (TREC) assay to screen for severe combined immunodeficiency disorder (SCID). The objective of this study was to perform a retrospective chart review of 199 infants referred to a single institution for abnormal TREC on NYS NBS between 2010 and 2017. Statistical analysis included analysis of variance, logistic regression models, chi-square, and linear mixed models. One hundred ninety-nine infants were found to have a TREC value of fewer than 200 copies/μL on NYS NBS. Infants were stratified as primary immunodeficiency (PID) (n = 54), immunocompetent (n = 133), lost to follow-up (n = 8), or deceased (n = 4). PID included SCID (n = 3), DiGeorge (n = 6), idiopathic lymphopenia (IL) (n = 44), and other syndromes associated with lymphopenia (n = 3). The 3 SCID cases were identified and brought to treatment, although all experienced significant infections. The study population was found to be predominately non-Hispanic, African American, and male. There was a difference in the average TREC values among those with immunocompetence (83 copies/μL), IL (81 copies/μL), and PID (40 copies/μL) (p < 0.05). On follow-up of 40 patients with IL, patients typically did not have severe infections during first few years of life. This study demonstrates that TREC value can be used to stratify infants for further confirmatory testing to exclude PID. Risk factors, such as stressful prenatal/postnatal conditions, prematurity, race, and sex may affect TREC value but cannot explain all causes of lymphopenia. This study may assist providers in risk stratifying the likelihood of PID with an abnormal TREC and determining the extent of the initial work up that is necessary at the time of a newborn's presentation.