Purpose: This paper presents the evaluation of the following psychometric properties of the Modified Rivermead Mobility Index (MRMI): face/content validity, responsiveness, test-retest reliability, inter-rater reliability and internal consistency. This mobility scale represents a further development of the Rivermead Mobility Index (RMI). In its new form the scoring was adapted from a two-point to a six-point scale. The number of test items was reduced from fifteen to eight items in order to measure mobility-related items that physiotherapists consider being essential for demonstrating treatment effects in patients following a stroke.
Method: A consensus exercise with forty-two physiotherapists attending a stroke care conference established face/content validity. Inter-rater and test-retest reliability were examined by assessing thirty patients by two independent raters selected from a pool of eight physiotherapists in two different settings, an elderly care unit and a stroke rehabilitation unit. All patients were hospitalised and had experienced a stroke within the past six weeks. Responsiveness was examined by calculating the effect size statistic on the admission and discharge score of sixteen acute patients following stroke.
Results: The results showed that the modified RMI was: responsive to change (effect size = 1.15), stable when tested on two occasions (paired t-test = 0.732; p = 0.47), highly reliable between raters (ICC = 0.98; p < 0.001) with high internal consistency (Cronbach's alpha = 0.93).
Conclusions: These results suggest that when using the Modified RMI to assess patients in the early stages following stroke, similar results can be obtained by different raters, regardless of experience. However there needs to be a difference of more than 4.5 points (degree of measurement error at 95% confidence level) in the overall score to detect true changes in the patient's level of mobility.