title: A new two-tier strength assessment approach to the diagnosis of weakness in intensive care: an observational study.
abstract: BACKGROUND
  Intensive care unit-acquired weakness (ICU-AW) is a significant problem. There is currently widespread variability in the methods used for manual muscle testing and handgrip dynamometry (HGD) to diagnose ICU-AW. This study was conducted in two parts. The aims of this study were: to determine the inter-rater reliability and agreement of manual muscle strength testing using both isometric and through-range techniques using the Medical Research Council sum score and a new four-point scale, and to examine the validity of HGD and determine a cutoff score for the diagnosis of ICU-AW for the new four-point scale.
  
  
  METHODS
  Part one involved evaluation of muscle strength by two physical therapists in 29 patients ventilated >48 hours. Manual strength testing was performed by both physical therapists using two techniques: isometric and through range; and two scoring systems: traditional six-point Medical Research Council scale and a new collapsed four-point scale. Part two involved assessment of handgrip strength conducted on 60 patients. A cutoff score for ICU-AW was identified for the new four-point scoring system.
  
  
  RESULTS
  The incidence of ICU-AW was 42% (n = 25/60) in this study (based on HGD). In part one the highest reliability and agreement was observed for the isometric technique using the four-point scale (intraclass correlation coefficient = 0.90: kappa = 0.72 respectively). Differences existed between isometric and through-range scores (mean difference = 1.76 points, P = 0.005). In part two, HGD had a sensitivity of 0.88 and specificity of 0.80 for diagnosing ICU-AW. A cutoff score of 24 out of 36 points was identified for the four-point scale.
  
  
  CONCLUSIONS
  The isometric technique is recommended with reporting on a collapsed four-point scale. Because HGD is easy to perform and sensitive, we recommend a new two-tier approach to diagnosing ICU-AW that first tests handgrip strength with follow-up strength assessment using the isometric technique for muscle strength testing if handgrip strength falls below cutoff scores. Whilst our results for the four-point scale are encouraging, further research is required to confirm the findings of this study and determine the validity of the four-point scoring system and cutoff score developed of less than 24 out of 36 before recommending adoption into clinical practice.
authors.affiliation: School of Health Sciences, Physiotherapy Department, The University of Melbourne, Level 7 Alan Gilbert Building, 161 Barry Street, Parkville, 3010, VIC, Australia. parrys@unimelb.edu.au.
authors.forename: Selina M
authors.initials: SM
authors.lastname: Parry
authors.affiliation: Department of Physiotherapy, Austin Health, 145 Studley Road, Heidelberg, 3084, VIC, Australia. sue.berney@austin.org.au.|Institute for Breathing and Sleep, Austin Health, 145 Studley Road, Heidelberg, 3084, VIC, Australia. sue.berney@austin.org.au.
authors.forename: Sue
authors.initials: S
authors.lastname: Berney
authors.affiliation: School of Health Sciences, Physiotherapy Department, The University of Melbourne, Level 7 Alan Gilbert Building, 161 Barry Street, Parkville, 3010, VIC, Australia. Catherine.granger@unimelb.edu.au.|Institute for Breathing and Sleep, Austin Health, 145 Studley Road, Heidelberg, 3084, VIC, Australia. Catherine.granger@unimelb.edu.au.
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Granger
authors.affiliation: Department of Physiotherapy, Austin Health, 145 Studley Road, Heidelberg, 3084, VIC, Australia. Danielle.dunlop@austin.org.au.
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Dunlop
authors.affiliation: Department of Physiotherapy, Austin Health, 145 Studley Road, Heidelberg, 3084, VIC, Australia. laura.murphy@austin.org.au.
authors.forename: Laura
authors.initials: L
authors.lastname: Murphy
authors.affiliation: School of Health Sciences, Physiotherapy Department, The University of Melbourne, Level 7 Alan Gilbert Building, 161 Barry Street, Parkville, 3010, VIC, Australia. d.el-ansary@unimelb.edu.au.
authors.forename: Doa
authors.initials: D
authors.lastname: El-Ansary
authors.affiliation: Department of Physiology, The University of Melbourne, Grattan Street, Parkville, 3010, VIC, Australia. rkoopman@unimelb.edu.au.
authors.forename: René
authors.initials: R
authors.lastname: Koopman
authors.affiliation: School of Health Sciences, Physiotherapy Department, The University of Melbourne, Level 7 Alan Gilbert Building, 161 Barry Street, Parkville, 3010, VIC, Australia. l.denehy@unimelb.edu.au.|Institute for Breathing and Sleep, Austin Health, 145 Studley Road, Heidelberg, 3084, VIC, Australia. l.denehy@unimelb.edu.au.
authors.forename: Linda
authors.initials: L
authors.lastname: Denehy
mesh_terms: D000368:Aged; D003422:Critical Care; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D053581:Muscle Strength Dynamometer; D018908:Muscle Weakness / Q000175:diagnosis* / Q000503:physiopathology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012121:Respiration, Artificial