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Observational Study
. 2025 May;30(3):e70018.
doi: 10.1111/nicc.70018.

An optimal cut-off point for the Chelsea Critical Care Physical Assessment Tool to diagnose intensive care unit-acquired weakness in patients with mechanical ventilation: A multicentre observational study

Yuchen Wu  1   2   3 , Yatao Liu  2   3 , Guoqiang Wang  2   3 , Ang Zheng  4 , Zhigang Zhang  2   3 , Huaping Wei  2   3 , Xin Wang  1   5
Affiliations
Observational Study

An optimal cut-off point for the Chelsea Critical Care Physical Assessment Tool to diagnose intensive care unit-acquired weakness in patients with mechanical ventilation: A multicentre observational study

Yuchen Wu et al. Nurs Crit Care. 2025 May.

Abstract

Background: The Chelsea Critical Care Physical Assessment Tool (CPAx) may be an optimal tool for diagnosing intensive care unit-acquired weakness (ICU-AW). However, we do not know the cut-off point for the diagnosis of ICU-AW.

Aim: To ascertain the best cut-off point for CPAx to diagnose ICU-AW in adult patients with mechanical ventilation.

Study design: A multicentre, prospective cross-sectional study. Participants were recruited from five ICUs in China that ranged from 20 June 2021 to 31 July 2023. The Medical Research Council Sum Scale (MRC-ss) <48 was taken as the standard to calculate the area under the curve (AUC) of CPAx. The cut-off point was determined by the maximum value of Youden Index (YImax). The kappa (κ) test was used to test the consistency of the MRC-ss and CPAx.

Results: The AUC at baseline, weaning and discharge time point was 0.87 (95% CI 0.81-0.93), 0.96 (95% CI 0.92-0.99) and 0.91 (95% CI 0.86-0.96), respectively. Correspondingly, The YImax was 0.62, 0.91 and 0.65. The best cut-off point of CPAx score to diagnose ICU-AW at baseline, weaning and discharge time point was 30.5 (sensitivity = 72%, specificity = 89%), 31.5 (sensitivity = 95%, specificity = 90%) and 31.5 (sensitivity = 94%, specificity = 71%), respectively. Due to the CPAx being an ordinal scale, it was determined preliminarily that the cut-off point for the CPAx to diagnose ICU-AW was 31 points. We took CPAx ≤31 and MRC-ss <48 as criteria to diagnose ICU-AW and test the consistency of MRC-ss and CPAx. The results showed that there was no significant difference in the incidence of ICU-AW at different time points.

Conclusions: The optimal cut-off point for the CPAx to diagnose ICU-AW is a score of 31 and it has good sensitivity and specificity.

Relevance to clinical practice: The CPAx ≤31 score to diagnose ICU-acquired weakness (ICU-AW) has good sensitivity and specificity, and it can help to predict the risk of ICU-AW and guide medical personnel to make interventions.

Keywords: critical care nursing; intensive care unit; mechanical ventilation; muscle weakness; sensitivity and specificity.

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