Effective newborn screening for deadly immunodeficiency
Published online: May 1, 2021
Massachusetts was among the first states to begin screening for a deadly disease known as severe combined immunodeficiency (SCID). This disorder is sometimes referred to as “Bubble Boy disease” given the notoriety of a patient with SCID who was kept infection-free though isolation in a sterile environment. Patients with SCID lack T cells, making them extremely susceptible to infection. If left untreated, these patients typically die within the first year of life. While advances over the last few decades have made this disease curable through bone marrow transplantation or gene therapy, the chance of survival drops considerably if an infection is contracted prior to transplant. Unfortunately, as infants with SCID appear normal at birth, most have been identified only after diagnosis of life-threatening infection.
In 2009, in an effort to improve outcomes through detection of infants with SCID prior to infection, Massachusetts became one of the first states in the nation to include SCID in the universal newborn screening program. Newborn screening, performed using a few drops of blood collected from all infants shortly after birth, is used to identify infants with rare, but treatable disorders. Screening for SCID uses a rapid and inexpensive test that looks for the presence of T cell recombination excision circles (TRECs) in blood collected from patients. Patients without detectable TRECs have a greatly increased risk of having SCID.
In The Journal of Allergy and Clinical Immunology: In Practice, Hale, Platt and colleagues describe outcomes from the first 10 years of SCID newborn screening in Massachusetts. During this time, the program identified 9 infants with SCID (~1 in 80,000 births), as well as 7 additional infants with other severe immunodeficiencies that did not meet diagnostic criteria for SCID (~1 in 50,000 births overall). No known cases of SCID were missed. All patients with SCID were treated using bone marrow transplantation or gene therapy leading to 100% survival. (In the 10 years prior, only 4 of 7 infants identified with SCID in Massachusetts survived). Hale and colleagues also outline the immunological features of patients who were found to have SCID in comparison to those with less severe forms of immunodeficiency, quite valuable to clinicians who are evaluating infants with a positive newborn screen. Recognizing that false positive tests cause increased cost to the healthcare system and anxiety to families, Hale and colleagues also describe key measures that were taken to minimize false positive testing. Using these measures, only 11% of infants identified by the screen could be characterized as “false positives.”
Based on the success of states like Massachusetts, by the end of 2018, all US states were screening for SCID. While universal newborn screening has only been available nationwide for the past several years, the Massachusetts group provides an early look at outcomes based on 10 years of experience. The results are highly encouraging, making it clear that infants with SCID can be quickly identified, thus increasing the chances of a cure.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.