# Infant Lung Function in Cystic Fibrosis: A Real‐World Study

## TL;DR

This study examines lung function in infants with cystic fibrosis and finds that clinical decisions are more influenced by symptoms than by lung function tests.

## Contribution

The study provides real-world data on lung function in infants with cystic fibrosis and its impact on clinical management.

## Key findings

- Abnormal lung function was observed in 31% of 3-month-olds, 28% of 1-year-olds, and 19% of 2-year-olds.
- Clinical management changes were more common in cases with abnormal lung function and recent positive microbiology or abnormal chest findings.
- Only 12% of cases with abnormal lung function but normal clinical findings led to management changes.

## Abstract

Previous research showed that lung function abnormalities are common in infants with cystic fibrosis (IwCF) but real‐world data are missing.

This single‐center retrospective study analyzed infant lung function results from IwCF born in 2012–2018. The tests were conducted at Great Ormond Street Hospital, London, as part of routine care at 3 months, 1 year, and 2 years of age. Z‐scores for SF6 Lung Clearance Index (zLCI), plethysmographic FRC (zFRCpleth) and FEV0.5 were derived. Microbiology and antibiotics prescription from 3 months before lung function assessments, up to the closest medical review following the lung function encounter, were analyzed, along with changes in management advised by the physician.

A total of 126 lung function encounters (n = 43 at 3 months, 46 at 1 year, 37 at 2 years) from 60 IwCF were included. LCI was abnormal (zLCI > 1.96) in 31% (12/39) of 3‐month‐olds (mean± zLCI 1.21 ± 1.08), 28% (12/43) of 1‐year‐olds and 19% (7/36) of 2‐year‐olds (mean± zLCI 1.13 ± 1.10). Among 74 cases with recent positive microbiology or abnormal chest findings at medical review, 100% (31/31) of those with abnormal lung function and 86% (37/43) of those with normal lung function (p = 0.04) had a recent antibiotic prescription or a change in clinical management. Conversely, in encounters with abnormal lung function but normal clinical findings, management changes occurred in only 12% (2/16) of cases.

In this real‐word cohort of IwCF, clinical management was mainly influenced by clinical findings and only marginally by abnormal lung function (elevated FRC or LCI).