What is the Rankin Scale?
The modified Rankin Scale (mRS) is a 7-level clinical outcome scale (scores 0-6) that measures global disability and functional independence after stroke, with lower scores indicating better outcomes. 1
Scale Structure and Scoring
The mRS consists of seven distinct levels that assess a patient's ability to perform daily activities and their degree of independence: 1
- Score 0: No symptoms at all
- Score 1: No significant disability despite symptoms; able to carry out all usual duties and activities
- Score 2: Slight disability; unable to carry out all previous activities but able to look after own affairs without assistance
- Score 3: Moderate disability; requiring some help but able to walk without assistance
- Score 4: Moderately severe disability; unable to walk without assistance and unable to attend to own bodily needs without assistance
- Score 5: Severe disability; bedridden, incontinent, and requiring constant nursing care and attention
- Score 6: Dead
Clinical Interpretation and Use
The mRS is the most widely employed outcome measure in acute stroke trials and clinical practice. 1 It functions as a global functional health index with a strong emphasis on physical disability rather than a pure handicap measure. 2
Outcome Categories
Clinical trials and guidelines typically categorize mRS scores into outcome groups: 1
- Excellent outcome: mRS 0-1 (no symptoms to no significant disability)
- Good outcome: mRS 0-2 (includes slight disability but independent in self-care)
- Poor outcome: mRS 3-6 (moderate disability to death)
Key Clinical Distinctions
The scale differentiates patients based on three critical dimensions of functioning: 1
- Impairments (body function): Determines transitions between scores 0→1 (presence of symptoms) and 5→6 (death)
- Activity limitations: Determines transitions between scores 3→4 (ambulation and bodily self-care) and 4→5 (constant nursing care requirement)
- Participation restrictions: Determines transitions between scores 1→2 (ability to work) and 2→3 (need for assistance)
Important Clinical Considerations
Mobility and disability in activities of daily living are the strongest determinants of mRS scores, showing greater association (Somers' D 0.60-0.74) than cognitive and social functioning (Somers' D 0.34-0.47). 2 Physical disability in daily activities explains approximately 67% of the variance in Rankin scores. 2
Timing of Assessment
The mRS demonstrates time-dependent sensitivity in differentiating functional recovery: 3
- At 10 days post-stroke, the scale primarily distinguishes only extreme grades (no disability vs. severe disability)
- At 3 months, it can differentiate independent patients with slight disability from dependent patients with marked disability
- Maximum sensitivity is reached at 6 months post-stroke, when the scale can clearly distinguish independence (mRS 0-2) from dependence (mRS 3-5) 3
Reliability in Practice
Real-world interobserver agreement for the mRS is modest, with approximately 70% overall agreement (kappa 0.55-0.58) between raters, even when one or both are certified in its use. 4 This level of consistency is considered sufficient for observational studies and stroke registries but emphasizes the importance of standardized training. 4