The Respective Roles of Lung Clearance Index and Magnetic Resonance Imaging in the Clinical Management of Patients with Cystic Fibrosis

State-of-the-art review of lung imaging in cystic fibrosis with recommendations for pulmonologists and radiologists from the "iMAging managEment of cySTic fibROsis" (MAESTRO) consortium

OBJECTIVE

Imaging represents an important noninvasive means to assess cystic fibrosis (CF) lung disease, which remains the main cause of morbidity and mortality in CF patients. While the development of new imaging techniques has revolutionised clinical practice, advances have posed diagnostic and monitoring challenges. The authors aim to summarise these challenges and make evidence-based recommendations regarding imaging assessment for both clinicians and radiologists.

STUDY DESIGN

A committee of 21 experts in CF from the 10 largest specialist centres in Italy was convened, including a radiologist and a pulmonologist from each centre, with the overall aim of developing clear and actionable recommendations for lung imaging in CF. An a priori threshold of at least 80% of the votes was required for acceptance of each statement of recommendation.

RESULTS

After a systematic review of the relevant literature, the committee convened to evaluate 167 articles. Following five RAND conferences, consensus statements were developed by an executive subcommittee. The entire consensus committee voted and approved 28 main statements.

CONCLUSIONS

There is a need for international guidelines regarding the appropriate timing and selection of imaging modality for patients with CF lung disease; timing and selection depends upon the clinical scenario, the patient's age, lung function and type of treatment. Despite its ubiquity, the use of the chest radiograph remains controversial. Both computed tomography and magnetic resonance imaging should be routinely used to monitor CF lung disease. Future studies should focus on imaging protocol harmonisation both for computed tomography and for magnetic resonance imaging. The introduction of artificial intelligence imaging analysis may further revolutionise clinical practice by providing fast and reliable quantitative outcomes to assess disease status. To date, there is no evidence supporting the use of lung ultrasound to monitor CF lung disease.

Ventilatory efficiency and its clinical and prognostic value in adults with cystic fibrosis

Cystic fibrosis, due to the absence or abnormal function of the cystic fibrosis transmembrane conductance regulator, is the most common life-limiting autosomal recessive genetic disorder among the Caucasian population. The lungs are particularly affected due to thick and tenacious mucus causing parenchymal anomalies ranging from bronchiectasis, progressive airflow limitation, respiratory infections, lung destruction and ultimately respiratory failure. Despite the remarkable advances in treatment that have greatly improved survival, most patients experience progressive exercise curtailment, with the consequence that a growing number of patients with cystic fibrosis will be referred for exercise-based evaluations in the forthcoming years. Cardiopulmonary exercise testing, in particular, is a useful tool to assess the mechanisms of exercise intolerance in individual patients that may have treatment and prognostic implications. In this review, we will focus on ventilatory efficiency and its clinical and prognostic value in adults with cystic fibrosis.

Toward the Establishment of New Clinical Endpoints for Cystic Fibrosis: The Role of Lung Clearance Index and Cardiopulmonary Exercise Testing

As Cystic Fibrosis (CF) treatment advances, research evidence has highlighted the value and applicability of Lung Clearance Index and Cardiopulmonary Exercise Testing as endpoints for clinical trials. In the context of these new endpoints for CF trials, we have explored the use of these two test outcomes for routine CF care. In this review we have presented the use of these methods in assessing disease severity, disease progression, and the efficacy of new interventions with considerations for future research.

A two-center analysis of hyperpolarized 129Xe lung MRI in stable pediatric cystic fibrosis: Potential as a biomarker for multi-site trials

BACKGROUND

The ventilation defect percent (VDP), measured from hyperpolarized (HP) 129Xe magnetic resonance imaging (MRI), is sensitive to functional changes in cystic fibrosis (CF) lung disease. The purpose of this study was to measure and compare VDP from HP 129Xe MRI acquired at two institutions in stable pediatric CF subjects with preserved lung function.

METHODS

This retrospective analysis included 26 participants from two institutions (18 CF, 8 healthy, age range 10-17). Pulmonary function tests, N2 multiple breath washout (to measure lung clearance index, LCI), and HP 129Xe MRI were performed. VDP measurements were compared between two trained analysts using mean-anchored linear binning. Correlations were investigated for VDP compared to the forced expiratory volume in one second (FEV1) and LCI.

RESULTS

VDP measurements agreed for the two analysts with an intraclass correlation coefficient of 0.99. In the combined dataset, VDP measured by Analyst 1 was 5.96 ± 1.82% and 15.96 ± 6.76% for the healthy and CF groups, respectively (p = .0004). Analyst 2 showed similar differences between healthy and CF (p = .0003). VDP measured by either analyst was shown to correlate with FEV1 (R2 = 0.33, p = .003; and R2 = 0.26, p = .009 for Analysts 1 and 2, respectively) and LCI (R2 = 0.76, p < .0001; and R2 = 0.77, p < .0001 for Analysts 1 and 2, respectively).

CONCLUSION

HP 129Xe MRI provides a robust measurement of ventilation heterogeneity in stable pediatric CF subjects at two sites. Since measurements performed at two sites yielded similar VDP values with near-identical values between different analysts, implementation of the technique in multi-center trials in CF appears feasible.