Flow Cytometry Confirmation Post Newborn Screening for SCID in England.

Kimberly C Gilmour

doi:10.3390/ijns8010001

Abstract

An evaluation program for newborn screening for Severe Combined Immunodeficiency began in England in September 2021 based on TREC analysis. Flow cytometry is being used as the follow up diagnostic test for patients with low/absent TRECS. The immunology laboratories have established a protocol and values for diagnosing SCID, other T lymphopenias and identifying healthy babies. This commentary describes the flow cytometry approach used in England to define SCID, T lymphopenia and normal infants after a low TREC result. It provides background to the flow cytometry assays being used and discusses the need to monitor and potentially change these values over time.

Highlights

Infants with severe combined immunodeficiency (SCID) usually present in the first year of life with recurrent, opportunistic infections as well as failure to thrive
Since outcomes for SCID are significantly improved if diagnosed at birth [1], a number of countries have introduced screening programs for SCID based on measuring the number of T cell receptor excision circles (TRECS) that are present in the blood spot on a Guthrie card
Measurement of TRECS is a screening test that identifies babies with SCID as well as other conditions, including Di George syndrome, CHARGE, idiopathic T lymphopenia and a number of normal infants will be referred for further investigation [2]

Summary

Introduction

Infants with severe combined immunodeficiency (SCID) usually present in the first year of life with recurrent, opportunistic infections as well as failure to thrive. Their immunology is characterised as lacking naïve T cells. Measurement of TRECS is a screening test that identifies babies with SCID as well as other conditions, including Di George syndrome, CHARGE, idiopathic T lymphopenia and a number of normal infants will be referred for further investigation [2]. FACs is a well validated methodology that uses fluorescently labelled antibodies to bind to cell makers. The resulting changes in light patterns are detected These can be visualised and quantified by computer software enabling characterisation and enumeration of the cells

Flow Cytometry for SCID in England

Comparison of English Values with Other SCID Screening Programs

Findings

Summary