Minimal important differences of EORTC QLQ-C30 for metastatic breast cancer patients: Results from a randomized clinical trial

Purpose To establish minimal important differences (MIDs) for the European Organisation for Research and Treatment for Cancer Quality of life Questionnaire core 30 (EORTC QLQ-C30) in patients with metastatic breast cancer. Methods The dataset was obtained from the SELECT BC-CONFIRM randomized clinical trial. Anchors obtained from patients (transition items) and clinicians (performance status) were used for anchor-based methods. Anchors obtained through 6 months after starting treatment were used for this analysis. Correlation coefficients of anchor and change in QLQ-C30 and effect size were used to qualify for estimating MIDs. Mean change method and generalized estimating equation were applied to estimate MIDs. Distribution-based methods were used for comparison. Results We analyzed a dataset of 154 metastatic breast cancer patients. MIDs were estimated in 8 of 15 scales of QLQ-C30. Estimated MIDs for within-group improvement varied from 7 to 15 and those for deterioration varied from − 7 to − 17. Estimated MIDs for between-group improvement varied from 5 to 11 and those for deterioration varied from − 5 to − 8 across QLQ-C30 scales. Patient-reported anchors were more susceptible to early changes in health status than clinician-reported anchors. Conclusion We provided the MIDs of the QLQ-C30 using both patient- and clinicians-reported anchors measured in a randomized trial of Japanese patients with metastatic breast cancer. We recommend patient-reported anchors for anchor-based estimation of MID. Our results can aid patients and clinicians, as well as researchers, in the interpretation of QLQ-C30.

Mind the methods of determining minimal important differences: three critical issues to consider

ObjectiveClinical trialists, meta-analysts and clinical guideline developers are increasingly using minimal important differences (MIDs) to enhance the interpretability of patient-reported outcome measures (PROMs). Here, we elucidate three critical issues of which MID users should be aware. Improved understanding of MID concepts and awareness of common pitfalls in methodology and reporting will better inform the application of MIDs in clinical research and decision-making.MethodsWe conducted a systematic review to inform the development of an inventory of anchor-based MID estimates for PROMs. We searched four electronic databases to identify primary studies empirically calculating an anchor-based MID estimate for any PROM in adolescent or adult populations across all clinical areas. Our findings are based on information from 338 studies reporting 3389 MIDs for 358 PROMs published between 1989 and 2015.ResultsWe identified three key issues in the MID literature that demand attention. (1) The profusion of terms representing the MID concept adds unnecessary complexity to users’ task in identifying relevant MIDs, requiring meticulous inspection of methodology to ensure estimates offered truly reflect the MID. (2) A multitude of diverse methods for MID estimation that will yield different estimates exist, and whether there are superior options remains unresolved. (3) There are serious issues of incomplete presentation and reporting of key aspects of the design, methodology and results of studies providing anchor-based MIDs, which threatens the optimal use of these estimates for interpretation of intervention effects on PROMs.ConclusionsAlthough the MID represents a powerful tool for enhancing the interpretability of PROMs, realising its full value will require improved understanding and reporting of its measurement fundamentals.

Evaluating the credibility of anchor based estimates of minimal important differences for patient reported outcomes: instrument development and reliability study

Objective To develop an instrument to evaluate the credibility of anchor based minimal important differences (MIDs) for outcome measures reported by patients, and to assess the reliability of the instrument. Design Instrument development and reliability study. Data sources Initial criteria were developed for evaluating the credibility of anchor based MIDs based on a literature review (Medline, Embase, CINAHL, and PsycInfo databases) and the experience of the authors in the methodology for estimation of MIDs. Iterative discussions by the team and pilot testing with experts and potential users facilitated the development of the final instrument. Participants With the newly developed instrument, pairs of masters, doctoral, or postdoctoral students with a background in health research methodology independently evaluated the credibility of a sample of MID estimates. Main outcome measures Core credibility criteria applicable to all anchor types, additional criteria for transition rating anchors, and inter-rater reliability coefficients were determined. Results The credibility instrument has five core criteria: the anchor is rated by the patient; the anchor is interpretable and relevant to the patient; the MID estimate is precise; the correlation between the anchor and the outcome measure reported by the patient is satisfactory; and the authors select a threshold on the anchor that reflects a small but important difference. The additional criteria for transition rating anchors are: the time elapsed between baseline and follow-up measurement for estimation of the MID is optimal; and the correlations of the transition rating with the baseline, follow-up, and change score in the patient reported outcome measures are satisfactory. Inter-rater reliability coefficients (ĸ) for the core criteria and for one item from the additional criteria ranged from 0.70 to 0.94. Reporting issues prevented the evaluation of the reliability of the three other additional criteria for the transition rating anchors. Conclusions Researchers, clinicians, and healthcare policy decision makers can consider using this instrument to evaluate the design, conduct, and analysis of studies estimating anchor based minimal important differences.