Severe Combined Immunodeficiency (SCID) Screening in Arizona: Lessons Learned from the First 2 Years

Abstract Purpose:The incidence of severe combined immunodeficiency (SCID) in the United States was reported as 1 in 58,000 live births. In Arizona, it was anticipated that newborn screening would identify two to four cases of SCID per year. This estimate did not consider ethnic nuances in Arizona, with higher percentages of American Indian and Hispanic populations compared to national percentages. The true incidence of SCID and non SCID T-cell lymphopenia have not previously been reported in Arizona. Methods:A retrospective chart review was performed of abnormal SCID Newborn Screening (NBS) tests from January 1, 2018 to December 31, 2019, using data from the Arizona Department of Health Service and the Phoenix Children’s Hospital’s electronic medical record [IRB# 20-025]. Results: Seven infants were diagnosed with SCID, yielding an incidence of 1 in 22,819 live births. Four of these infants had Artemis type SCID. Eighteen infants were identified with an abnormal initial NBS which ultimately did not lead to a diagnosis of SCID. Four of these infants were diagnosed with congenital syndromes associated with T-cell lymphopenia. Infants of Hispanic ethnicity were over-represented in this cohort. Conclusion: NBS in Arizona confirmed an incidence more than 2.5 times that reported nationally. This increased incidence is likely reflective of Arizona’s unique population profile, with a higher percentage of American Indian population. The findings in our non-SCID cohort are in alignment with previously published data, except for a higher than anticipated number of infants of Hispanic/Latino ethnicity, likely related to Arizona’s higher percentage of Hispanic/Latino population.