Correlations between measures of ALS respiratory function: is there an alternative to FVC?

Area of Science:

• Neurology
• Pulmonology
• Biostatistics

Background:

• Longitudinal study assessing respiratory function in Amyotrophic Lateral Sclerosis (ALS) patients across six European sites.
• Measures include forced vital capacity (FVC), slow vital capacity (SVC), peak cough flow (PCF), and Sniff nasal inspiratory pressure (SNIP).
• Interim analysis motivated by COVID-19 restrictions and the need to evaluate SNIP as a surrogate for aerosol-generating procedures.

Purpose of the Study:

• To evaluate Sniff nasal inspiratory pressure (SNIP) as a potential surrogate for aerosol-generating procedures in ALS.
• To analyze the correlations and rates of decline among different respiratory function measures in ALS.
• To determine if SNIP can differentiate between spinal and bulbar onset ALS.

Main Methods:

• Prospective observational study with 3-monthly assessments of FVC, SVC, PCF, and SNIP.
• Data collected from March 2018 to March 2020.
• Bayesian multiple outcomes random-effects model used to analyze rates of decline; correlation analysis performed.

Main Results:

• 270 ALS cases and 828 assessments analyzed (Mean age 65.2 years; 32.6% Female; 60% King's stage 2).
• High correlation between FVC and SVC (0.95); SNIP showed lower correlations with FVC (0.53), SVC (0.54), and PCF (0.60).
• All measures declined significantly over time; SNIP demonstrated the fastest decline in the bulbar onset group.

Conclusions:

• SNIP is not a surrogate for FVC and SVC due to assessing different respiratory aspects.
• SNIP is a valuable complementary measure that declines linearly over time in ALS patients.
• SNIP effectively differentiates between spinal and bulbar onset ALS, showing a faster decline in bulbar onset.