Treatment success is the desired outcome in aphasia rehabilitation. However, to date, there is a lack of consensus on what defines a ‘successful’ result on a given aphasia outcome measurement instrument (OMI).
In this methodological paper, we present strategies for how to define and measure treatment success on a given OMI at the group level, as well as for an individual person with aphasia. The latter is particularly important when research findings from group studies are clinically implemented for individuals in rehabilitation.
We start by presenting methods to calculate the average statistically significant change across several (group) studies (e.g., standardised response mean difference, raw unstandardised mean difference) for a given OMI. Such metrics are useful to summarise an overall effect of the intervention of interest, particularly in meta-analyses. However, benchmarks based on group effects are not feasible for assessing an individual participant’s treatment success and thus for determining the proportion of patients who had a beneficial response to therapy (overall response rate of an intervention). We therefore recommend a distribution-based approach to determine benchmarks of statistically significant treatment response at the individual level, i.e., the ‘smallest detectable change’ for a given OMI, which refers to the smallest change that can be detected by the OMI beyond measurement error. However, the statistical significance of an individual treatment effect does not necessarily correspond to its clinical impact. This requires an additional indicator. The benchmark to determine a clinically relevant improvement on a given OMI is the ‘minimal important change’. The minimally important change which is defined as the smallest OMI change score perceived as important by the relevant stakeholder group (i.e., people with aphasia, their relatives/caregivers, clinicians). It therefore and thus requires relating the individual OMI change scores to ‘anchors’, i.e., meaningful external criteria, preferably based on patient perceived therapy success. Currently, there is no consensus regarding the optimal ‘anchors’ and their respective definition of clinically important change in aphasia outcome research.
Operationalising individual treatment success based on both statistically significant and (patient-reported) clinically meaningful benchmarks, with the latter preferably based on a patient-reported ‘anchor’, is a key priority in aphasia rehabilitation. Availability of such calibrated measures will (a) facilitate estimates of therapy response rate in intervention studies and thus optimise therapeutic decisions and (b) provide stakeholder groups (e.g., the society, the acute care stroke team, people with aphasia, family, clinicians, healthcare professionals and funders/insurers) with objective, statistically reliable and meaningful feedback on individual treatment response in the clinical setting.
|Publication status||Accepted/In press - 7 Dec 2021|