Lung MRIs work better than breathing tests to predict CF exacerbations: Study
Those with impaired lung ventilation on scans twice as likely to have flare-ups
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People with cystic fibrosis (CF) who show impaired lung ventilation — problems with air moving into and out of the lungs — are more than twice as likely to experience pulmonary exacerbations (PEx) over two years than those with normal ventilation, according to a new study that compared the use of lung MRIs with standard lung function tests.
In the study, such impairments were measured using VDP, or ventilation defect percent, which reflects the share of lung regions that inhaled air does not reach normally, and is obtained using specialized MRI scans. The researchers were testing lung MRIs against commonly used measures of lung function to determine which might be a better predictor.
The team found that abnormal VDP was far more common among people who later experienced a PEx, with higher values in those who had more frequent events. Further, unlike standard lung function measures, VDP remained a significant predictor of future PEx after adjusting for other factors, the researchers noted.
These findings indicate that “[functional] MRI may be well suited for patient monitoring” and predicting exacerbations, particularly in patients with “mild, gradual lung-function decline” for whom routine clinical tests may not be helpful, the researchers wrote.
The study, “Structural and functional pulmonary MRI to predict pulmonary exacerbations in Cystic Fibrosis,” was published in Chest by a team of researchers from the U.S. and Canada.
PEx, or flare-ups marked by worsening cough, increased sputum (phlegm), and shortness of breath, remain a major cause of lung function decline for people with CF. These episodes cause inflammation and structural damage that impair mucus clearance and set up a self-reinforcing cycle that increases vulnerability to future PEx.
“Therefore,” the researchers wrote, “the treatment, management, and prevention of PEx is essential for patient quality-of-life and prolonged lifespan.”
Available tools fail to reliably predict pulmonary exacerbations
Current clinical tools do not reliably predict when PEx will occur, however. Lung function tests such as FEV₁, which measure how much air a person can forcefully exhale in one second, often miss early disease because they are not sensitive to changes beginning in the small airways.
“These small airway abnormalities … may be important precursors to PEx and represent early obstruction or subclinical bacterial microcolonies,” the scientists wrote.
Imaging, such as MRI scans, can provide a more reliable way to detect these abnormalities and determine whether they affect breathing. Structural MRI can detect airway changes, while functional MRI can be used to map how different regions of the lung ventilate.
Still, whether these MRI measures can help predict future PEx is not known.
To fill this knowledge gap, the research team analyzed lung MRI scans from 106 people with CF, ages 6 to 45, acquired between March 2015 and June 2023 at Cincinnati Children’s Hospital Medical Center in Ohio.
Nearly all patients (94%) were white, non-Hispanic individuals. They were pretty evenly split by sex. Most (83%) carried at least one F508del mutation, the most common CF-causing variant, and half (51%) were on a CFTR modulator — a recently developed class of medications for CF — at the time of imaging. Nearly two-thirds (64%) had normal lung function, defined as an FEV₁ of 90% or higher.
Lung MRIs may help CF patients with gradual declines in function
Structural MRIs revealed a wide range of structural lung damage, from mild to severe. Bronchiectasis — when the airways become widened, building up mucus and increasing infection risk — was the most common abnormality. Mucus plugging and airway wall thickening, both signs of inflammation and obstruction, were also frequent.
VDP, as measured by functional MRI, was abnormal — defined as greater than 3% — in 69% of participants. VDP values ranged from 0% to 47%, with a median of 10%. Ventilation images frequently showed wedge-shaped or patchy regions of poor airflow, consistent with small-airway obstruction, the researchers noted.
Among the 98 participants with two-year follow-up data, 38 experienced at least one PEx. Those who later had a PEx began the study with poorer lung function and worse ventilation, showing a median VDP of 11% compared with 4% in those who remained exacerbation-free. Abnormal VDP was also more common in this group (79% vs. 53%). Surprisingly, the authors noted, no differences were observed in structural MRI measures between the two groups.
VDP rose progressively with PEx frequency, increasing from a median of 4% in those with no events and 6% in those with one or two, to 26% in those with three or more.
People with abnormal VDP experienced PEx almost three times more frequently than those with normal ventilation, with those with the most severe structural MRI changes — such as marked bronchiectasis or airway wall thickening — also showing more frequent events.
[Functional] MRI may be well-suited for predicting exacerbations in a new generation of patients with mild, gradual lung-function decline that is difficult to capture with clinical [lung] function tests.
Risk analysis showed that abnormal VDP more than doubled the likelihood of experiencing a PEx within two years. By one year, 17% of people with normal VDP had a PEx compared with 40% of those with abnormal VDP; by two years, the rates were 29% versus 54%.
In predictive modeling, incorporating imaging improved prediction accuracy relative to clinical data alone, according to the researchers. When prior exacerbations were considered, VDP remained a significant predictor of future PEx, whereas FEV₁ did not, the team found.
Overall, the results support the use of lung MRIs as a predictive tool, per the data.
“[Functional] MRI may be well-suited for predicting exacerbations in a new generation of patients with mild, gradual lung-function decline that is difficult to capture with clinical [lung] function tests,” the researchers concluded.
