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05-12-2022 | Letter to the Editor

Likely change indexes do not always index likely change; moreover, there is no need for them

Auteur: Berend Terluin

Gepubliceerd in: Quality of Life Research

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Excerpt

Peipert et al. [ 1] introduced the concept of “likely change index” (LCI) as a kind of reliable change index (RCI) [ 2] but with relaxed significance criteria. The RCI was defined as the change score, divided by √2 times the standard error of measurement (SEM). Essentially, the RCI represents a significance test of an individual change score by determining the probability ( p) of observing that change score if in reality there were no change (the null hypothesis H 0). If the RCI exceeds the critical value 1.96, p is smaller than 0.05, H 0 is rejected and the change score is assumed to represent real change (the alternative hypothesis H 1). To get a change score threshold to classify patients as reliably changed or not, the authors used a transformation of the RCI, the coefficient of repeatability (CR), calculated as critical value * √2 * SEM. The disadvantage of the “CR at the 95% confidence” is well known: it tends to misclassify many patients who feel they have changed and indeed may truly have changed, just because the amount of measurement error in the change score prevents reliably distinguishing real change from chance fluctuation at smaller change scores. Because the authors felt that, for some applications, it may be acceptable to be less certain that a change threshold is differentiable from measurement error, they introduced “relaxed” CRs at reduced confidence levels: 68%, based on the critical value 0.994, and 50%, based on the critical value 0.674, referring to these CRs as LCIs. The expression “likely change index” seems to suggest that real change is “likely” instead of “reliably” as with the RCI. It should be noted, however, that the proposed LCIs imply significance testing at p-values of 0.32 and 0.50, respectively, instead of 0.05 (which seems a bit awkward). …
Literatuur
2.
go back to reference Jacobson, N. S., & Truax, P. (1991). Clinical significance: A statistical approach to defining meaningful change in psychotherapy research. Journal of Consulting and Clinical Psychology, 59, 12–19. CrossRef Jacobson, N. S., & Truax, P. (1991). Clinical significance: A statistical approach to defining meaningful change in psychotherapy research. Journal of Consulting and Clinical Psychology, 59, 12–19. CrossRef
3.
go back to reference Goodman, S. (2008). A dirty dozen: Twelve p-value misconceptions. Seminars in Hematology, 45(3), 135–140. CrossRef Goodman, S. (2008). A dirty dozen: Twelve p-value misconceptions. Seminars in Hematology, 45(3), 135–140. CrossRef
4.
go back to reference Terwee, C. B., Peipert, J. D., Chapman, R., Lai, J. S., Terluin, B., Cella, D., Griffith, P., & Mokkink, L. B. (2021). Minimal important change (MIC): A conceptual clarification and systematic review of MIC estimates of PROMIS measures. Quality of Life Research, 30(10), 2729–2754. CrossRef Terwee, C. B., Peipert, J. D., Chapman, R., Lai, J. S., Terluin, B., Cella, D., Griffith, P., & Mokkink, L. B. (2021). Minimal important change (MIC): A conceptual clarification and systematic review of MIC estimates of PROMIS measures. Quality of Life Research, 30(10), 2729–2754. CrossRef
Metagegevens
Titel
Likely change indexes do not always index likely change; moreover, there is no need for them
Auteur
Berend Terluin
Publicatiedatum
05-12-2022
Uitgeverij
Springer International Publishing
Gepubliceerd in
Quality of Life Research
Print ISSN: 0962-9343
Elektronisch ISSN: 1573-2649
DOI
https://doi.org/10.1007/s11136-022-03314-9