Researchers have identified 3 trajectories of respiratory function based on changes in forced vital capacity (FVC) in patients with amyotrophic lateral sclerosis (ALS). These findings may ultimately assist in classifying patients with ALS based on respiratory progression, a study in the American Journal of Respiratory and Critical Care Medicine reports.

The study was a retrospective analysis of a cohort of patients with ALS (n=837) from a single center. Patients had a first clinic visit at the center between 2006 and 2015. A validation cohort from the Pooled Resource Open-Access ALS Clinical Trials (PROACT) database comprised the source population (n=7461). Various patient characteristics at baseline (first visit) were used as predictors of trajectory group membership. Trajectory of FVC percent of predicted normal, recorded at each visit and over time in months, was the primary outcome. A multistep process using the group-based trajectory model identified discrete groups of FVC trajectories over time.

A total of 3 trajectories of FVC over time were found, including stable low (n=397), rapid progressor (n=329), and slow progressor (n=111). Patients who were considered rapid progressors had shorter diagnosis delay compared with the slow progressors (0.7 years vs 0.9 years, respectively; P <.001). Additionally, rapid progressors had more bulbar-onset disease (806 vs 135; P <.001) as well as a lower ALS Functional Rating Scale – Revised (ALSFRS-R) total score at baseline (37±6 vs 40±5; P <.001) compared with slow progressors.

Relative to the slow progressors, the stable low group also had a shorter diagnosis delay (0.9 years vs 0.7 years, respectively; P <.001), more bulbar-onset disease (135 vs 660, respectively; P <.001), lower ALSFRS-R total score (40±5 vs 33±7, respectively; P <.001), and were more likely to present with an ALSFRS-R orthopnea score of <4 (P <.001). In the PROACT cohort, projected group membership was predictive of respiratory insufficiency (c-statistic=0.78; 95% CI, 0.76-0.79).

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A limitation of the study was the potential for measurement error, which may have affected FVC measurements.

“By further refining characteristics associated with different trajectories of respiratory function, we may tailor goals of care and respiratory interventions to provide personalized medicine for ALS.”

Reference

Ackrivo J, Hansen-Flaschen J, Jones BL, et al. Classifying amyotrophic lateral sclerosis patients by changes in forced vital capacity: a group-based trajectory analysis [published online July 19, 2019]. Am J Respir Crit Care Med. doi:10.1164/rccm.201902-0344OC