Lung Clearance Index Detects Deterioration Earlier, Study Finds
LCI measures how long it takes for tracer gas to clear the lungs
A measure of lung function called the lung clearance index can detect impaired lung function in children with cystic fibrosis (CF) at earlier ages than standard spirometry, a new study suggests.
The study, “Pulmonary exacerbations, airway pathogens, and long-term course of lung clearance index in children and young adults with Cystic Fibrosis,” was published in the journal Pediatric Pulmonology.
In CF and other diseases affecting the lungs, it is important to objectively measure lung function to track disease progression and guide treatment decisions.
A standard measure of lung function is spirometry, which involves measuring how much air someone can forcibly exhale in a breath or a set amount of time. This can be used to calculate measures such as forced expiratory volume in one second (FEV1).
The lung clearance index, or LCI, is another test of lung function that involves measuring how long it takes for a tracer gas to be cleared from the lungs. A higher LCI value indicates poorer lung function.
In this study, a group of researchers in Greece conducted a retrospective analysis of data for 76 young people with CF evaluated at their clinic from 2011 to 2018. The patients ranged in age from younger than 2 to nearly 24, and 50% were male.
Over the study period, these patients completed a total of 1,272 clinical visits, including 1,047 spirometry tests to assess FEV1, and 1,151 multiple-breath washout tests to measure LCI.
The scientists conducted a battery of statistical analyses to assess how FEV and LCI measurements related to clinical outcomes over time.
Both lung function measurements tended to be poorer in older patients. This is generally consistent with the typical course of CF; lung function tends to worsen over time. A worsening of LCI was evident at an earlier age than for FEV1.
“We demonstrated that a significant deterioration in LCI was detected in patients older than 11 years, while a significant deterioration in FEV1 was detected later in patients over 16 years,” the researchers wrote. They added other studies have also demonstrated “the superiority of LCI in early detecting lung disease progression.”
Analyses also showed worse scores for both FEV1 and LCI were associated with greater risk of exacerbations — times when lung function becomes suddenly worse, often due to an infection — and a greater likelihood of colonization with certain bacteria that can cause disease in people with CF, namely Pseudomonas Aeruginosa and Stenotrophomonas Maltophilia.
Overall, the researchers concluded that LCI is a useful tool for monitoring in CF, and it may be more useful than the more commonly used FEV1 in earlier stages of lung disease.
“The lung clearance index has been introduced to monitor CF patients in earlier stages, but FEV1% and its decline rate are still considered the most significant predictor of mortality in CF patients,” they wrote. “When the disease progression gets to the point of affecting FEV1, the lung damage tends to be irreversible.”