Limitations of sniff nasal pressure as an outcome measurement in amyotrophic lateral sclerosis patients in a clinical trial

Respiration. 2012;84(4):306-11. doi: 10.1159/000339415. Epub 2012 Jul 28.


Background: The forced vital capacity (FVC) is an established measure in amyotrophic lateral sclerosis (ALS) clinical trials. Recently the sniff nasal inspiratory pressure (SNIP) test has been increasingly used as a respiratory measure.

Objectives: It was the aim of this study to assess the feasibility of SNIP as an outcome measure in a phase III clinical trial with a lead-in design.

Methods: Twenty patients were enrolled in a randomized clinical trial. FVC, SNIP in sitting (SNIPsitt) and supine (SNIPsup) positions, and the ALS functional rating scale score (ALSFRS-R) were measured every 4 weeks.

Results: Complete data were available for 19 patients over 5 months. Baseline values were normal for FVC (101 ± 14%) but abnormal for SNIPsitt and SNIPsup (84 ± 34% and 82 ± 33%). While FVC and ALSFRS-R declined in parallel, SNIPsitt measures declined significantly less compared to ALSFRS-R (p < 0.05) and FVC (p < 0.001) up to 4 months after enrollment. Over 50% of patients still had values equal to or above baseline SNIPsitt measures after 3 months despite abnormal baseline values.

Conclusions: The delayed decline in SNIP measurements suggests a learning effect over time. The optimal number of SNIPs in ALS clinical trials has yet to be determined. SNIP measures should be used with caution in trials with a lead-in design.

Publication types

  • Clinical Trial, Phase III
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Aged
  • Amyotrophic Lateral Sclerosis / physiopathology*
  • Feasibility Studies
  • Female
  • Humans
  • Inhalation*
  • Male
  • Middle Aged
  • Nose / physiopathology*
  • Outcome Assessment, Health Care
  • Posture
  • Pressure*
  • Vital Capacity