title: Respiratory Muscle Strength as a Predictive Biomarker for Survival in Amyotrophic Lateral Sclerosis.
abstract: Biomarkers for survival in amyotrophic lateral sclerosis (ALS) would facilitate the development of novel drugs. Although respiratory muscle weakness is a known predictor of poor prognosis, a comprehensive comparison of different tests is lacking.
  
  
  
  To compare the predictive power of invasive and noninvasive respiratory muscle strength assessments for survival or ventilator-free survival, up to 3 years.
  
  
  
  From a previously published report respiratory muscle strength measurements were available for 78 patients with ALS. Time to death and/or ventilation were ascertained. Receiver operating characteristic analysis was used to determine the cutoff point of each parameter.
  
  
  
  Each respiratory muscle strength assessment individually achieved statistical significance for prediction of survival or ventilator-free survival. In multivariate analysis sniff trans-diaphragmatic and esophageal pressure, twitch trans-diaphragmatic pressure (Tw Pdi), age, and maximal static expiratory mouth pressure were significant predictors of ventilation-free survival and Tw Pdi and maximal static expiratory mouth pressure for absolute survival. Although all measures had good specificity, there were differing sensitivities. All cutoff points for the VC were greater than 80% of normal, except for prediction of 3-month outcomes. Sequential data showed a linear decline for direct measures of respiratory muscle strength, whereas VC showed little to no decline until 12 months before death/ventilation.
  
  
  
  The most powerful biomarker for mortality stratification was Tw Pdi, but the predictive power of sniff nasal inspiratory pressure was also excellent. A VC within normal range suggested a good prognosis at 3 months but was of little other value.
authors: 1 National Institute for Heath Research Respiratory Biomedical Research Unit at the Royal Brompton and Harefield National Health Service Foundation Trust and Imperial College, London, United Kingdom.
authors: Michael I
authors: MI
authors: Polkey
authors: 2 Department of Respiratory Medicine, King's College Hospital, London, United Kingdom.
authors: Rebecca A
authors: RA
authors: Lyall
authors: 3 BioMarin Pharmaceutical Inc., Novato, California.
authors: Ke
authors: K
authors: Yang
authors: 3 BioMarin Pharmaceutical Inc., Novato, California.
authors: Erin
authors: E
authors: Johnson
authors: 4 Brighton and Sussex Medical School, Trafford Centre for Biomedical Research, University of Sussex, Falmer, East Sussex, United Kingdom.
authors: P Nigel
authors: PN
authors: Leigh
authors: 5 King's Health Partners, London, United Kingdom; and.|6 Division of Asthma, Allergy and Lung Biology, King's College London School of Medicine, London, United Kingdom.
authors: John
authors: J
authors: Moxham
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis / Q000401:mortality* / Q000503:physiopathology; D015415:Biomarkers; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D011379:Prognosis; D016016:Proportional Hazards Models; D012372:ROC Curve; D012132:Respiratory Muscles / Q000503:physiopathology
chemical_list: D015415:Biomarkers
keywords: amyotrophic lateral sclerosis; diaphragm; maximal inspiratory pressure; sniff nasal inspiratory pressure; survival