MRI scans, lung clearance index favored as lung tests for children
Greater sensitivity seen in non-invasive ways of monitoring young patients
Two non-invasive tests — MRI scans and the lung clearance index (LCI) — were more sensitive to early lung disease in children with cystic fibrosis (CF) than standard lung function tests, a study from Switzerland reports.
Better ways of evaluating lung health in infants and children are needed, given the effectiveness of newborn screening programs for CF and the growing availability at young ages of CFTR modulator therapies, which work to “reduce disease severity, [and] slow progression,” the researchers wrote.
Study findings, they added, “support the use of LCI and MRI as sensitive, non-invasive methods for early detection and monitoring of lung disease in children with CF.”
The study, “Lung structural and functional impairments in young children with cystic fibrosis diagnosed following newborn screening – A nationwide observational study,” was published in the Journal of Cystic Fibrosis.
Current standard lung tests, like spirometry, are difficult for young children
CF is a genetic disease that affects the lungs early in life, but standard assessments to monitor lung disease are not ideal for the routine clinical management of young patients.
Lung function tests like spirometry, which measures the amount of air that can be rapidly exhaled, are difficult to perform in young children and may not be sensitive enough to detect early lung disease, the scientists noted. Moreover, repeated CT chest scans throughout childhood increase risks associated with radiation exposure.
“Therefore, sensitive, non-invasive surveillance endpoints are needed to monitor lung disease onset and progression,” the researchers, based at the University of Bern, argued.
MRI scans and LCI are emerging as non-invasive methods for assessing mild lung dysfunction. LCI measures how long it takes a person to “clear” an inhaled tracer gas from their lungs, with longer times associated with structural changes in the airways.
Researchers used Swiss cohort study data to assess MRI and LCI outcomes in children diagnosed with CF through newborn screening.
A group of 79 children with CF was recruited alongside 75 healthy children as a control group, matched by age, height, weight, and body mass index (body fat content). Three patients were on a CFTR modulator therapy at the time of the study.
A morphology score was calculated from MRI scans, with higher scores indicating more abnormal lung structure. The percentage of the lung with impaired ventilation was reported as the ventilation defect percentage (VDP), and the amount of impaired perfusion (blood flow through the lungs) was scored by the perfusion defect percentage (QDP).
As a comparison, the standard spirometry FEV1 test, measuring the volume of air exhaled in one second after a deep breath, was also assessed.
Lung issues seen in 47%-48% of patients on MRI scans, 4.8% with FEV1
Analysis revealed that values for LCI, MRI morphology score, VDP, and QDP all were significantly higher, meaning worse, in children with CF compared with healthy controls. At the same time, no differences in FEV1 were seen between the two groups.
About half of the CF children had signs of functional impairment on MRI, with 47% having VDP values above the normal limit, and 48% with QDP values above normal. A total of 1 in 3 (30%) children with CF had an MRI morphology score above the upper limit of normal, compared with abnormal FEV1 readings being seen in about 1 in 20 (4.8%) of these young patients .
LCI, but not FEV1, significantly associated with the total MRI morphology score, airway wall thickening, mucus plugging, and ventilation and perfusion defects. Likewise, the total MRI morphology score, airway thickening, and mucus plugging correlated with ventilation and perfusion defects.
Pulmonary exacerbations (periods of acute symptom worsening) and hospitalizations during the first year of life independently linked with poorer lung function and structural disease in later childhood. Conversely, cough and lung infections during infancy did not associate with later childhood outcomes.
Pulmonary exacerbations in infants also associated with later LCI worsening, while hospitalizations associated with higher MRI morphology scores and ventilation defects later on.
Throughout childhood, hospitalizations for severe respiratory issues were related to MRI structural and functional problems in early childhood. By contrast, other respiratory events and airway infections did not affect lung function or MRI outcomes.
In the year before study enrollment, pulmonary exacerbations linked with greater lung impairment evident on tests like LCI, MRI, VDP, and QDP. Hospitalizations and increased coughing also associated with increased lung impairment on MRI scans, as did colonization with Staphylococcus aureus bacteria.
“We demonstrated that LCI and functional and structural lung MRI outcomes are sensitive and non-invasive surveillance strategies in children with CF following newborn screening,” the researchers concluded.
“The mild lung disease detected in our cohort can encourage patients and their families to continue early specialist CF treatment and therapies (e.g. physiotherapy, inhalation therapies) to preserve their lung function throughout childhood,” the team added.
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