Comprehensive Assessment of Disability Post-Stroke Using the Newly Developed Mifunction Scale

Background and Purpose: The modified Rankin Scale (mRS) is the most widely used primary outcome measure in acute stroke trials. However, substantial inter-observer variability impairs outcome assessment and reduces power of clinical trials. Guided by the International Classification of Functioning, Disability and Health (ICF), we developed a comprehensive, hierarchical assessment tool (miFUNCTION) to address the shortcomings of the mRS and deliver a more thorough understanding of disability following stroke (figure 1). Methods: The construct validity of miFUNCTION was initially established in a pilot study of patients at an outpatient stroke prevention clinic that had been diagnosed with stroke within 60 days. To further assess criterion validity, miFUNCTION was compared against the mRS and other outcome measures within the ESCAPE trial. Logistic regression analysis with miFUNCTION as an outcome was used to demonstrate the benefit of endovascular treatment. Results: The pilot study showed moderate inter-observer agreement (k=0.585, p<0.005) but near perfect correlation between miFUNCTION and mRS (ρ=0.821, p<0.05). The correlation of miFUNCTION and mRS was near perfect again in the ESCAPE trial (ρ=0.944). Effect size of multivariable models using mRS (adjusted OR 3.45, 95% CI 2.05 – 5.78) and miFUNCTION (adjusted OR 3.32, 95% CI 1.99 – 5.55) as an outcome measure for the ESCAPE trial patients was similar. Conclusions: miFUNCTION is strongly associated with the degree of disability following stroke both in an outpatient setting and clinical trial. Further work remains to assess sensitivity to change and to improve the inter-observer reliability of the scale.