Primary immunodeficiency testing in a Massachusetts tertiary care NICU: persistent challenges in the extremely...

Prematurity presents a diagnostic challenge in interpreting primary immunodeficiency (PID) testing.

We retrospectively reviewed the charts of all infants in our level IV referral neonatal intensive care unit (NICU) in Massachusetts, with immunologic testing performed from 2006 to 2018.

The overall rate of PID testing was enriched in our population, with 1% of admitted patients having extended immunologic testing. The addition of TREC (T cell receptor excision circle) newborn screening in Massachusetts in 2009 increased the proportion of infants tested for PID in our NICU by 3-fold (1.21% post-newborn screening (NBS) vs. 0.46% pre-NBS). A majority of the term and late preterm (≥34 weeks) infants (31 of 41, 76%), as well as very premature (29-33 weeks) infants (12 of 17, 71%), who had immune testing, had a genetic diagnosis associated with secondary immunodeficiency or a PID. Most infants who were born extremely premature (EP, <29 weeks) (25 of 29, 86%) had no identifiable cause of immunodeficiency besides prematurity, despite a mean postmenstrual age of 40.1 weeks at the time of testing.

Persistent immune derangements were present within a subgroup of the EP population through term postmenstrual age. EP infants with significant infectious history and abnormal immune testing at term-corrected age should be considered for genetic testing.

The role of immunologic testing in the premature population is unclear, we therefore reviewed the records of all infants in our NICU who had immunologic testing, to rule out immunodeficiency, done from 2006 to 2018. The addition of newborn screening for SCID in 2009 doubled the number of infants who had immune investigations. The extremely premature cohort included many infants with persistent immune derangements through term-corrected gestational age, suggesting a persistent effect of prematurity on immune development and potential function. We propose that former premature infants with clinical evidence of immunodeficiency and sustained immune abnormalities by term-corrected age undergo genetic testing for immunodeficiency.