Assessing Responsiveness of Health Measurements. Ian McDowell, INTA, Santiago, March 20, 2001. Link Purpose of Measure to Validation Method. For example: In a diagnostic instrument, inter-rater and test-retest reliability are important;
INTA, Santiago, March 20, 2001
1. Use a t-test and report statistically significant differences as indicators of responsiveness
2. Removing the n from the denominator to make independent of sample size
3. Denominator can be SD of the baseline scores, or of scores among stable subjects, or of change in scores.
SEM = SD1 * %(1-")
Impact of including Alpha in Effect Size Calculation
(at difference of 1.5 and SD of 3)
1. Apply the measurement; select change threshold seen as important by clinical experts. How much would the outcome have to change before they would alter treatment?
2. Present clinicians with written scenarios and compare each with the previous one. MCID = average difference in scores between pairs rated as ‘a little less’ or ‘a little more’.
1. Establish MID or MCID. Group patients who improve (or deteriorate) > MID and compare to rest using the measure
2. Various statistics:
0.0 0.2 0.4 0.6 0.8 1.0
1-specificity (false positives)
ROC Curve for 3 Instruments in Detecting an MCID
Notional Size of an MCID at Various Levels of Overall Health