A new two-tier strength assessment approach to the diagnosis of weakness in intensive care

A new two-tier strength assessment approach to the diagnosis of weakness in intensive care: An observational study. Critical Care, 2015, 19: 52 

Parry, S.M., et al.

http://ccforum.com/content/pdf/s13054-015-0780-5.pdf

Intensive care unit acquired weakness (ICUAW) is a significant problem. There is currently widespread variability in the methods used for manual muscle testing and handgrip dynamometry (HGD) to diagnose ICUAW. 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 ICUAW for the new four-point scale.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 sixpoint Medical Research Council scale and a new collapsed four-point scale. Part two involved assessment of handgrip strength conducted on 60 patients. A cut-off score for ICUAW was identified for the new four-point scoring system. 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 fourpoint 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 ICUAW. A cut-off score of 24/36 points was identified for the four-point scale. 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 ICUAW 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 cut off score developed.