title: Limitations of sniff nasal pressure as an outcome measurement in amyotrophic lateral sclerosis patients in a clinical trial.
abstract: 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.
  
  
  OBJECTIVE
  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.
authors: Neuromuscular Diseases Unit/ALS Clinic, Kantonsspital St. Gallen, Switzerland.
authors: M
authors: M
authors: Bauer
authors: D
authors: D
authors: Czell
authors: S
authors: S
authors: Hartmann
authors: B
authors: B
authors: Goldman
authors: D
authors: D
authors: Müller
authors: M
authors: M
authors: Weber
mesh_terms: D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000503:physiopathology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D001239:Inhalation; D008297:Male; D008875:Middle Aged; D009666:Nose / Q000503:physiopathology*; D017063:Outcome Assessment, Health Care; D011187:Posture; D011312:Pressure; D014797:Vital Capacity