COSMOS: Interrater and Intrarater Reliability Study of a Novel Outcome Measure.

Area of Science:

• Neurology
• Rehabilitation Medicine
• Clinical Outcome Measurement

Background:

• Minor stroke patients frequently report dissatisfaction with outcomes despite good scores on traditional scales like the modified Rankin Scale.
• Existing outcome measures may not fully capture the functional limitations and impact on life pursuits experienced by individuals after a minor stroke.

Purpose of the Study:

• To develop and assess the reliability of a new functional outcome measure, the Canadian Outcome Scale for Minor Stroke (COSMOS), specifically designed for patients with minor stroke.
• To evaluate the interrater and intrarater reliability of the COSMOS scale.

Main Methods:

• The Canadian Outcome Scale for Minor Stroke (COSMOS), a 7-point scale, was developed to assess functional outcomes beyond basic activities of daily living.
• One hundred test case vignettes were created, and 33 stroke clinicians (physicians, fellows, research nurses/staff) graded 20 cases twice after a wash-out period.
• Interrater and intrarater reliability were evaluated using percentage agreement, Cohen κ, weighted κ, and intraclass correlation coefficient.

Main Results:

• The COSMOS scale demonstrated substantial interrater reliability (80.5% agreement, Cohen κ=0.77) and almost-perfect intrarater reliability (87.1% agreement, Cohen κ=0.85).
• Weighted κ values indicated almost perfect agreement for both interrater (0.88) and intrarater (0.92) reliability.
• The overall chance-adjusted agreement using intraclass correlation coefficient was 0.95, with consistent results across different clinician subgroups.

Conclusions:

• The newly developed Canadian Outcome Scale for Minor Stroke (COSMOS) exhibits substantial interrater and intrarater reliability.
• The COSMOS scale is a promising tool for evaluating functional outcomes in minor stroke patients and warrants further investigation in clinical trials and cohort studies.