Background and Aims: Modified Rankin Scale (mRS) is a single-dimensional ordinal scale encompassing a wide range of functional outcomes.  Quality of life scales and Barthel Index (BI) are multivariate instruments where both the total of individual domain scores and their multivariate “signature” combinations provide meaningful patient information. We aimed to describe and compare these multivariate “signatures” within and across individual mRS categories. 

Methods: mRS scores, two domains of BI (Selfcare and Mobility), and four domains of Assessment of Quality of Life AQoL-4D (Independent Living, Relationships, Mental Health and Senses) at 3 months from A Very Early Rehabilitation Trial (AVERT) were utilised. The differences in individual BI and AQoL-4D domain scores across mRS categories were investigated using Kruskal-Wallis test and Receiver Operator Characteristics curves analysis. Domain score-by-mRS category interactions were investigated using random effects linear regression models with respective interaction terms. 

Results: For both AQoL-4D and BI, individual domain scores were significantly different across mRS categories (p<0.0001).  The only individual domains with excellent discrimination (ROC>0.8) between sequential mRS categories were: AQoL-4D Independent Living domain for mRS 2vs3 (AUC 0.86) and mRS 3vs4 (AUC 0.92), and both BI domains for mRS 3vs4 (AUC 0.89 and 0.91) and 4vs5 (AUC 0.83 and 0.85). There was a significant domain-by-mRS interaction (p<0.0001) for both BI and AQoL-4D.

Conclusions: Our findings assist clinically relevant in-depth interpretation of mRS, by emphasising the multivariate nature of patient outcomes behind a single mRS score, where different individual mRS categories display significantly different AQOL-4D and BI domain “signatures”. 

Trial registration number: ACTRN12606000185561

CONSTRUCT VALIDITY OF THE UTILITY-WEIGHTED MODIFIED RANKIN SCALE AS A PRIMARY OUTCOME MEASURE IN STROKE TRIALS