# First pilot study for newborn screening of severe T and B lymphopenias in Colombia

## TL;DR

This study is the first in Colombia to screen newborns for lymphopenias using blood samples, aiming to detect immune deficiencies early.

## Contribution

The study introduces a pilot newborn screening method for congenital lymphopenias using TRECs and KRECs in Colombia.

## Key findings

- Six patients with suspected lymphopenia had undetectable or very low TREC levels.
- A positive correlation was found between TREC/KREC values from different filter papers.
- Low TREC levels were associated with low birth weight, and KREC levels negatively correlated with prematurity.

## Abstract

Congenital lymphopenias cause increased susceptibility to infections in children apparently healthy at birth. Earlier detection of these conditions would facilitate prompt treatment, prevent potentially serious disease complications and early deaths, and save healthcare resources.

To perform a pilot study for neonatal screening of congenital lymphopenias by the quantification of TREC and KREC -T- and B-cell receptor excision circles- in peripheral blood samples from newborns in Medellín, Colombia.

Blood samples from 1,092 newborns and six referred patients with suspected lymphopenia were collected by heel or toe-finger prick and dropped onto a filter paper. Thereafter, DNA was extracted and levels of TRECs and KRECs were measured by qPCR.

The six patients with suspected lymphopenia showed undetectable or very low TREC levels. All newborns screened presented normal TREC and KREC levels. A positive correlation was found between TREC or KREC values quantified from two different filter papers. Detectable levels of the receptor excision circles decrease considerably after 24 weeks of the dried blood spot sample storage. We identified a positive association between low TREC levels and low birth weight; and a negative correlation between KREC values and prematurity. Finally, no statistical differences were found between TREC or KREC levels and delivery method.

We describe the first preliminary study for the early detection of lymphopenias in Colombia. We proposed to use a cut-off value of 119 and 69 copies/pl blood of TREC and KREC, respectively for future newborn screening programs in our country.