Anchor-based minimal important difference values are often sensitive to the distribution of the change score

PURPOSE

Anchor-based studies are today the most popular approach to determine a minimal important difference value for an outcome variable. However, a variety of construction methods for such values do exist. This constitutes a challenge to the field. In order to distinguish between more or less adequate construction methods, meaningful minimal requirements can be helpful. For example, minimal important difference values should not reflect the intervention(s) the patients are exposed to in the study used for construction, as they should later allow to compare interventions. This requires that they are not sensitive to the distribution of the change score observed. This study aims at investigating to which degree established construction methods fulfil this minimal requirement.

METHODS

Six constructions methods were considered, covering very popular and recently suggested methods. The sensitivity of MID values to the distribution of the change score was investigated in a simulation study for these six construction methods.

RESULTS

Five out of six construction methods turned out to yield MID values which are sensitive to the distribution of the change score to a degree that questions their usefulness. Insensitivity can be obtained by using construction methods based solely on an estimate of the conditional distribution of the anchor variable given the change score.

CONCLUSION

In future the computation of MID values should be based on construction methods avoiding sensitivity to the distribution of the change score.

The minimal important difference of patient-reported outcome measures related to female urinary incontinence: a systematic review

BACKGROUND

The minimal important difference is a valuable metric in ascertaining the clinical relevance of a treatment, offering valuable guidance in patient management. There is a lack of available evidence concerning this metric in the context of outcomes related to female urinary incontinence, which might negatively impact clinical decision-making.

OBJECTIVES

To summarize the minimal important difference of patient-reported outcome measures associated with urinary incontinence, calculated according to both distribution- and anchor-based methods.

METHODS

This is a systematic review conducted according to the PRISMA guidelines. The search strategy including the main terms for urinary incontinence and minimal important difference were used in five different databases (Medline, Embase, CINAHL, Web of Science, and Scopus) in 09 June 2021 and were updated in January 09, 2024 with no limits for date, language or publication status. Studies that provided minimal important difference (distribution- or anchor-based methods) for patient-reported outcome measures related to female urinary incontinence outcomes were included. The study selection and data extraction were performed independently by two different researchers. Only studies that reported the minimal important difference according to anchor-based methods were assessed by credibility and certainty of the evidence. When possible, absolute minimal important differences were calculated for each study separately according to the mean change of the group of participants that slightly improved.

RESULTS

Twelve studies were included. Thirteen questionnaires with their respective minimal important differences reported according to distribution (effect size, standard error of measurement, standardized response mean) and anchor-based methods were found. Most of the measures for anchor methods did not consider the smallest difference identified by the participants to calculate the minimal important difference. All reports related to anchor-based methods presented low credibility and very low certainty of the evidence. We pooled 20 different estimates of minimal important differences using data from primary studies, considering different anchors and questionnaires.

CONCLUSIONS

There is a high variability around the minimal important difference related to patient-reported outcome measures for urinary incontinence outcomes according to the method of analysis, questionnaires, and anchors used, however, the credibility and certainty of the evidence to support these is still limited.

Minimal important difference of the 12-item World Health Organization Disability Assessment Schedule (WHODAS) 2.0 in persons with chronic low back pain

BACKGROUND

The World Health Organization Disability Assessment Schedule 2.0 12-item survey (WHODAS-12) is a questionnaire developed by the WHO to measure functioning across health conditions, cultures, and settings. WHODAS-12 consists of a subset of the 36 items of WHODAS-2.0 36-item questionnaire. Little is known about the minimal important difference (MID) of WHODAS-12 in persons with chronic low back pain (LBP), which would be useful to determine whether rehabilitation improves functioning to an extent that is meaningful for people experiencing the condition. Our objective was to estimate an anchor-based MID for WHODAS-12 questionnaire in persons with chronic LBP.

METHODS

We analyzed data from two cohort studies (identified in our previous systematic review) conducted in Europe that measured functioning using the WHODAS-36 in adults with chronic LBP. Eligible participants were adults with chronic LBP with scores on another measure as an anchor to indicate participants with small but important changes in functioning over time [Short-form-36 Physical Functioning (SF36-PF) or Oswestry Disability Index (ODI)] at baseline and follow-up (study 1: 3-months post-treatment; study 2: 1-month post-discharge from hospital). WHODAS-12 scores were constructed as sums of the 12 items (scored 0-4), with possible scores ranging from 0 to 48. We calculated the mean WHODAS-12 score in participants who achieved a small but meaningful improvement on SF36-PF or ODI at follow-up. A meaningful improvement was an MID of 4-16 on ODI or 5-16 on SF36-PF.

RESULTS

Of 70 eligible participants in study 1 (mean age = 54.1 years, SD = 14.7; 69% female), 18 achieved a small meaningful improvement based on SF-36 PF. Corresponding mean WHODAS-12 change score was - 3.22/48 (95% CI -4.79 to -1.64). Of 89 eligible participants in study 2 (mean age = 65.5 years, SD = 11.5; 61% female), 50 achieved a small meaningful improvement based on ODI. Corresponding mean WHODAS-12 change score was - 5.99/48 (95% CI - 7.20 to -4.79).

CONCLUSIONS

Using an anchor-based approach, the MID of WHODAS-12 is estimated at -3.22 (95% CI -4.79 to -1.64) or -5.99 (95% CI - 7.20 to -4.79) in adults with chronic LBP. These MID values inform the utility of WHODAS-12 in measuring functioning to determine whether rehabilitation or other health services achieve a minimal difference that is meaningful to patients with chronic LBP.

Novel clinically meaningful scores for the ICIQ-UI-SF and ICIQ-FLUTS questionnaires in women with stress incontinence

AIM

To establish, for the first time, the clinically important differences for the ICIQ-UI-SF and ICIQ-FLUTS questionnaires following surgical and conservative treatments for stress-predominant urinary incontinence in women.

METHODS

Data from the SIMS and OPAL randomised controlled trials were analysed using an anchor-based method. Clinically important difference (CID; score change indicating a successful outcome) and minimal important difference (MID; score change indicating the smallest noticeable difference) were estimated using the PGI-I scale as the anchor.

RESULTS

For ICIQ-UI-SF, following surgical management, CIDs were 5.0 (95%CI 4.3, 5.6) at 1 year and 4.9 points (95%CI 4.2, 5.5) at 3 years, while following conservative management, CIDs were 4.0 (95%CI 3.4, 4.5) at 1 year and 4.6 points (95%CI 4.0, 5.2) at 2 years. For ICIQ-FLUTS, the CID was 3.4 points (95%CI 2.9, 4.0) at 1 year for both surgical and conservative management. MIDs for ICIQ-UI-SF, after surgical treatment, were 4.7 (95% CI 3.2, 6.1) at 1 year and 1.6 points (95%CI -0.2, 3.0) at 3 years, and after conservative treatment they were 1.7 (95% CI 1.0, 2.5) at 1 year and 1.9 points (95%CI 1.1, 2.7) at 2 years. For ICIQ-FLUTS, MIDs were 1.8 (95% CI 0.6, 3.1) at 1 year and 3.2 points (95%CI 2.0, 4.4) at 2 years after surgical treatment, and 1.3 (95%CI 0.6, 1.9) at 1 year and 1.9 points (95%CI 1.1, 2.6) at 2 years after conservative treatment.

CONCLUSION

Our study is the first to establish the CID for the ICIQ-UI-SF and ICIQ-FLUTS that women would associate with a successful outcome 3-years post-surgery and 2-years post-conservative treatment of stress-predominant urinary incontinence. The MID was lower following conservative compared to surgical treatment.

Patient-Reported Outcome Measure Use in Guidelines Published by the American Academy of Ophthalmology: A Review

TOPIC

We reviewed the use of patient-reported outcome measures (PROMs) in the treatment of ophthalmologic conditions as recommended by the Clinical Practice Guidelines (CPGs) published by the American Academy of Ophthalmology (AAO).

CLINICAL RELEVANCE

Patient-reported outcome measures are standardized instruments that provide information regarding a patient's health status or health-related quality of life. Patient-reported outcome measures are increasingly used to inform study end points in ophthalmology studies. However, the extent to which PROMs are ultimately informing patient management recommendations in ophthalmology as part of CPGs remains an area of evidence gap.

METHODS

We included all CPGs published by the AAO from inception to June 2022. We also included all primary studies and systematic reviews cited in the treatment sections of the CPGs evaluating treatment of an ophthalmic condition. The primary outcome was the frequency of PROMs discussed in CPGs and in cited studies evaluating treatment. Secondary outcomes included frequency of minimal important difference (MID) use to contextualize PROM results and percentage of strong and discretionary recommendations supported by PROMs. We published a study protocol a priori on PROSPERO (CRD42022307427). Reporting followed the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) guidelines. We assessed risk of bias using the Appraisal of Guidelines, Research and Evaluation II (AGREE II) instrument.

RESULTS

We identified 24 eligible CPGs, providing 2458 cited studies (2191 primary, 267 secondary) evaluating treatment of eye conditions. Ten CPGs (41.7%) reported consideration of PROMs. Of these, 31 of 94 (33%) recommendations were informed by studies evaluating a PROM as an outcome. Across all studies cited in the development of CPGs, 221 (9.0%) used PROMs as a primary or secondary outcome, of which 4 PROM results (1.8%) were interpreted using an empirically determined MID. Overall, the risk of bias was low for all CPGs.

CONCLUSIONS

Overall, outcomes of PROMs are seldom used in ophthalmology CPGs published by the AAO and in cited primary and secondary research on treatments. When PROMs were considered, their interpretation was seldom based on an MID. To improve patient care, guideline developers may consider incorporating PROMs and applicable MIDs to inform key outcomes when formulating treatment recommendations.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

The difference between statistical significance and clinical relevance. The case of minimal important change, non-inferiority trials, and smallest worthwhile effect

Clinical relevance and statistical significance are different concepts, linked via the sample size calculation. Threshold values for detecting a minimal important change over time are frequently (mis)interpreted as a threshold for the clinical relevance of a difference between groups. The magnitude of a difference between groups that is considered clinically relevant directly impacts the sample size calculation, and thereby the statistical significance in clinical study outcomes. Especially in non-inferiority trials the threshold for clinical relevance, i.e. the predefined margin for non-inferiority, is a crucial choice. A truly inferior treatment will be accepted as non-inferior when this margin is chosen too large. The magnitude of a clinically relevant difference between groups should be carefully considered, by determining the smallest effect for each specific study that is considered worthwhile. This means taking into account the (dis)advantages of both study interventions in terms of benefits, harms, costs, and potential side effects. This article clarifies common sources of confusion, illustrates the implications for clinical research with an example and provides specific suggestions to improve the design and interpretation of clinical research.

Factors associated with worsening sexual function during adjuvant endocrine therapy in a prospective clinic-based cohort of women with early-stage breast cancer

PURPOSE

Sexual function problems are common but under-reported among women receiving adjuvant endocrine therapy for breast cancer. Worsening scores on patient-reported outcomes (PROs) may identify those at risk for sexual function problems during treatment. We performed a secondary analysis of prospectively collected PROs in women receiving adjuvant endocrine therapy to identify factors associated with worsening sexual function.

METHODS

Women with stage 0-III breast cancer initiating adjuvant endocrine therapy participating in a prospective cohort completed PROs at baseline, 3, 6, 12, 24, 36, 48, and 60 months. Sexual function was evaluated by the MOS-SP measure. Other measures included PROMIS pain interference, fatigue, depression, anxiety, physical function, and sleep disturbance and the Endocrine Symptom Subscale of the FACT-ES. We evaluated associations between score worsening of at least the minimal important difference (MID) in PROMIS T-scores (4 points) and FACT-ES scores (5 points) with score worsening of at least the MID in MOS-SP scores (8 points) using logistic regression.

RESULTS

Among 300 participants, 45.7% experienced ≥ 8-point worsening of MOS-SP score at any time point compared to baseline. Worsening endocrine symptoms (OR 1.34, 95% CI 1.22-1.49, p < 0.001), worsening physical function (OR 1.09, 95% CI 1.00-1.18, p = 0.06), and prior mastectomy (OR 1.45, 95% CI 0.94-2.23, p = 0.09) were associated with MOS-SP score worsening by at least the MID.

CONCLUSION

Worsening endocrine symptoms and physical function identified on PROs are associated with worsening sexual function during adjuvant endocrine therapy. Routine assessment of these domains with PROs may identify women at risk for sexual function problems.

TRIAL REGISTRATION NUMBER

NCT01937052; Date of Registration: 09/09/2013.

PROMs Following Root Canal Treatment and Surgical Endodontic Treatment

The FDI is currently working on developing a tool to encompass patient-reported outcome measures (PROMs) within the overall assessment of outcomes of endodontic treatment. The outcome of endodontic treatment has traditionally been determined by various clinical and radiographic criteria. However, these parameters do not address the impact of treatment on a patient's oral health-related quality of life (OHRQoL). OHRQoL, a crucial PROM, can be used to understand treatment outcome from a patient-centred perspective, thus improving clinician-patient communication whilst guiding decision-making. This focussed review aims to recount the OHRQoL of patients following nonsurgical root canal treatment and surgical endodontic treatment, with a specific focus on the minimal important difference (MID; the minimum score changes of an outcome instrument for a patient to register a clinically significant change in their OHRQoL and/or oral condition) and the methods used to determine it. The current evidence indicates that the OHRQoL of patients requiring root canal treatment is poorer than those without such need. Accordingly, the literature suggests that OHRQoL improves following nonsurgical or surgical endodontic treatment. However, study methodologies vary widely, and conclusions cannot be drawn with high confidence, nor can MID recommendations be provided. Well-designed clinical studies with baseline measurements and appropriate follow-up time frames are therefore needed. Despite that the literature is rife with outcome studies, research on PROMs is an area that deserves greater attention, particularly in relation to the MID. Determining the MID will facilitate the understanding of changes in outcome scores from the patients' perspective, thus allowing for more informed decision-making in clinical practice.

Minimal important difference and patient acceptable symptom state for the Numerical Rating Scale (NRS) for pain and the Patient-Rated Wrist/Hand Evaluation (PRWHE) for patients with osteoarthritis at the base of thumb

Background

The Numerical Rating Scale (NRS) and Patient-rated wrist/hand evaluation (PRWHE) are patient-reported outcomes frequently used for evaluating pain and function of the wrist and hand. The aim of this study was to determine thresholds for minimal important difference (MID) and patient acceptable symptom state (PASS) for NRS pain and PRWHE instruments in patients with base of thumb osteoarthritis.

Methods

Fifty-two patients with symptomatic base of thumb osteoarthritis wore a splint for six weeks before undergoing trapeziectomy. NRS pain (0 to 10) and PRWHE (0 to 100) were collected at the time of recruitment (baseline), after splint immobilization prior to surgery, and at 3, 6, 9 and 12 months after surgery. Four anchor-based methods were used to determine MID for NRS pain and PRWHE: the receiver operating characteristics (ROC) curve, the mean difference of change (MDC), the mean change (MC) and the predictive modelling methods. Two approaches were used to determine PASS for NRS pain and PRWHE: the 75^th percentile and the ROC curve methods. The anchor question for MID was the change perceived by the patient compared with baseline; the anchor question for PASS was whether the patient would be satisfied if the condition were to stay similar. The correlation between the transition anchor at baseline and the outcome at all time points combined was calculated using the Spearman’s rho analysis.

Results

The MID for NRS pain was 2.5 using the ROC curve method, 2.0 using the MDC method, 2.8 using the MC method, and 2.5 using the predictive modelling method. The corresponding MIDs for PRWHE were 22, 24, 10, and 20. The PASS values for NRS pain and PRWHE were 2.5 and 30 using the ROC curve method, and 2.0 and 22 using the 75th percentile method, respectively. The area under curve (AUC) analyses showed excellent discrimination for all measures.

Conclusion

We found credible MID estimates for NRS and PRWHE (including its subscales), although the MID estimates varied depending on the method used. The estimates were 20-30% of the range of scores of the instruments. The cut-offs for MID and PASS showed good or excellent discrimination, lending support for their use in future studies.

Trial registration

This clinimetrics study was approved by the Helsinki University ethical review board (HUS1525/2017).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-022-01600-1.

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.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11136-021-03074-y.

Isokinetic testing of quadriceps function in COPD: feasibility, responsiveness, and minimal important differences in patients undergoing pulmonary rehabilitation

•

Evaluation of isokinetic quadriceps testing in COPD is needed to assess its efficacy.

•

Isokinetic testing was performed incorrectly in a quarter of patients with COPD.

•

Quadriceps peak torque and total work improved following pulmonary rehabilitation.

•

Minimal important differences for peak torque and total work were determined.

Background

Isokinetic testing of peripheral muscle function is valid and reliable in patients with chronic obstructive pulmonary disease (COPD).

Objective

To evaluate whether and to what extent isokinetic testing of quadriceps function meets pre-defined test criteria in patients with COPD; to determine the response to pulmonary rehabilitation (PR), and to calculate minimal important differences (MIDs) of isokinetic quadriceps function.

Methods

Retrospective analysis of 2033 patients with COPD (age: 65±9 years, body mass index: 26±6 kg/m², FEV₁: 49±22% predicted) who followed a comprehensive PR program. Pre and post PR isokinetic quadriceps function was assessed with 30 maximal extension-flexion contractions at an angular speed of 90°/s on a computerized dynamometer. The chosen anchors were 6-min walk test and COPD assessment test.

Results

Pre PR, 27% of the patients performed the isokinetic test incorrectly. In male and female patients with a correct pre and post PR isokinetic test, peak torque (Δ=10±13 Nm or 9% and Δ=7±9 Nm or 10%, respectively) and total work (Δ=263±270 J or 14% and Δ=198±190 J or 15%, respectively) improved significantly. There was no change in work fatigue index following PR. Using distribution-based calculations, MID estimates for peak torque and total work ranged between 6–7 Nm and 97–135 J in males and between 4–5 Nm and 62–99 J in females.

Conclusions

Based on the current test criteria, three in four patients with COPD performed the isokinetic quadriceps test correctly during baseline PR assessment. Furthermore, peak torque and total work, but not work fatigue index, were responsive to PR and sex-specific MIDs were established.

Common errors in the design of orthopaedic trials: Has anything changed?

INTRODUCTION

The adoption of evidence-based orthopaedics has shifted the focus from expert base opinions and anecdotal evidence to a focus on integrating the best available clinical research. This shift has led to an increased focus on randomized controlled trials (RCTs) within the field. Although RCTs are considered the highest level of evidence, methodologic errors can introduce bias and limit the validity of the results. Early trials were hampered by lack of blinding, inadequate sample sizes and other design flaws. The objective of this review was to examine the current literature to determine if the design and execution of RCTs has improved.

DESIGN ERRORS

The awareness of the importance of sample size increased over time with substantially more trials reporting sample size calculations. However, many contemporary RCTs are still underpowered and fail to reach their calculated sample size. Given the challenges of surgically based RCTs, the majority of historical trials lacked blinding, increasing the risk of bias. There is evidence that there has been a concerted effort to increase the blinding in RCTs, particularly in outcome assessors. A more recent development in the design of surgical trials is the introduction of expertise-based trial designs in which patients are randomized to a surgeon with expertise in a particular intervention. These trials minimize the bias that can arise from differential expertise bias and have the potential to improve the validity and feasibility of RCTs. Finally, there has been an increased focus on the reporting of patient reported outcomes (PROs) in orthopaedic RCTs. Alongside this movement has been the development of minimal important differences (MIDs) to define the changes that are relevant and meaningful to patients. Both PROs and MIDs should be taken into consideration when calculating the sample size and study power in clinical trials.

CONCLUSIONS

Although marked improvements have been made in the design and implementation of trials, there is still considerable room for improvement. Adequately blinded and powered studies evaluating clinically important outcomes and differences should be key considerations in trial design moving forward.

Determining the minimal important change of the 6-minute walking test in Multiple Sclerosis patients using a predictive modelling anchor-based method

BACKGROUND

The minimal important change (MIC) of the 6-minute walk test (6MWT) is not clear for patients with Multiple Sclerosis (MS), hampering treatment evaluation. The aim of our study was therefore to determine the MIC of the 6MWT in MS patients.

METHODS

MS patients did the 6MWT using the instruction to walk at comfortable speed twice with approximately one year in between. After the second 6MWT they completed 3-point anchor question. The MIC_adjusted with a 95% confidence interval (CI) was calculated with the predictive modelling method with bootstrapping.

RESULTS

118 MS patients (mean age 48.2 years, 23.7% men) were included between September 2018 and October 2019. Mean 6MWT distance was 468 ± 112 m at baseline and 469 ± 115 m one year later. Twenty-three (19.5%) patients answered their walking distance improved, 43 (36.4%) answered it worsened. A MIC_adjusted for improvement of 19.7 m (95%CI 9.8-30.9 m) was found, and for deterioration of 7.2 m (95%CI -3.3-18.2 m).

CONCLUSIONS

Using the most sophisticated statistical method, the MIC_adjusted of the 6MWT in MS patients was 19.7 m for improvement, and 7.2 m for deterioration. This knowledge allows physiotherapists and physicians to evaluate if their treatment has led to a meaningful improvement for their MS patients or if walking of their patients has deteriorated.

Triangulation of multiple meaningful change thresholds for patient-reported outcome scores

PURPOSE

The notion of what constitutes meaningful differences or changes in patient-reported outcome scores is represented by meaningful change thresholds (MCTs). Applying multiple methods to estimate MCTs inevitably results in a range of estimates; however, a single estimate or small range is sought in practice to enable consistent interpretation of scores. While current recommendations for triangulation are appropriate in principle, the vital step of moving from all estimates to a value or small range lacks clarity and is subjective in nature. This article aims to review current triangulation approaches and provide more robust recommendations than what is currently available.

METHODS

Current approaches to perform triangulation are described and discussed. Anchor-based estimates are focussed upon due to their recognition as the most valid and developed approach. Recommendations for triangulation are provided.

RESULTS

A correlation-weighted average of MCT estimates is recommended to triangulate multiple MCT estimates derived from a single study into a single value, where increased weighting is given to stronger anchor measures. The choice of method to triangulate estimates from several published studies is highly dependent on the availability of information within the publications. MCTs designed for between-group differences, within-group changes, and within-individual changes should be considered separately.

CONCLUSION

The recommendations within this article provide a reliable and transparent approach to triangulation when a single value is sought, based on meta-analytic approaches. This approach is preferable to a simple mean of estimates where all are weighted equally, or through 'eyeballing' plotted estimates which is unreliable. We encourage researchers to adopt these methods, but to remain aware of the limitations within each method and further nuances in study design that result in heterogeneity. Sensitivity analyses with a range of plausible values are encouraged; however, the recommendations provide a suitable starting value for inferences. Unresolved issues in triangulation, requiring further exploration, are highlighted.

Methodological approach for determining the Minimal Important Difference and Minimal Important Change scores for the European Organisation for Research and Treatment of Cancer Head and Neck Cancer Module (EORTC QLQ-HN43) exemplified by the Swallowing scale

Purpose

The aim of this study was to explore what methods should be used to determine the minimal important difference (MID) and minimal important change (MIC) in scores for the European Organisation for Research and Treatment of Cancer Head and Neck Cancer Module, the EORTC QLQ-HN43.

Methods

In an international multi-centre study, patients with head and neck cancer completed the EORTC QLQ-HN43 before the onset of treatment (t1), three months after baseline (t2), and six months after baseline (t3). The methods explored for determining the MID were: (1) group comparisons based on performance status; (2) 0.5 and 0.3 standard deviation and standard error of the mean. The methods examined for the MIC were patients' subjective change ratings and receiver-operating characteristics (ROC) curves, predictive modelling, standard deviation, and standard error of the mean. The EORTC QLQ-HN43 Swallowing scale was used to investigate these methods.

Results

From 28 hospitals in 18 countries, 503 patients participated. Correlations with the performance status were |r|< 0.4 in 17 out of 19 scales; hence, performance status was regarded as an unsuitable anchor. The ROC approach yielded an implausible MIC and was also discarded. The remaining approaches worked well and delivered MID values ranging from 10 to 14; the MIC for deterioration ranged from 8 to 16 and the MIC for improvement from − 3 to − 14.

Conclusions

For determining MIDs of the remaining scales of the EORTC QLQ-HN43, we will omit comparisons of groups based on the Karnofsky Performance Score. Other external anchors are needed instead. Distribution-based methods worked well and will be applied as a starting strategy for analyses. For the calculation of MICs, subjective change ratings, predictive modelling, and standard-deviation based approaches are suitable methods whereas ROC analyses seem to be inappropriate.

Supplementary Information

The online version of this article (10.1007/s11136-021-02939-6) contains supplementary material, which is available to authorized users.

Responsiveness of five shoulder outcome measures at follow-ups from 3 to 24 months

Background

To assess responsiveness of five outcome measures at four different follow-ups in patients with SLAP II lesions of the shoulder.

Methods

119 patients with symptoms and signs, MRI arthrography and arthroscopic findings were included. The Western Ontario Shoulder Instability Index (WOSI), Oxford Instability Shoulder Score (OISS), EuroQol (EQ-5D3L), Rowe Score and Constant-Murley Score (CMS) were assessed at baseline, 3, 6, 12 and 24 months. The analysis contains both anchor-based and distribution-based methods, and hypothesis testing.

Results

Confidence intervals for ROC cut-off values, representing MID, for OISS, CMS and EQ-5D3L crossed zero at 3 months. Cut-off values were stable between 6- and 24-months follow-up. At 24-months ROC cut-off values (95% CI) were: Rowe 18 (13 to 24); WOSI 331 (289 to 442); OISS 9 (5 to 14); CMS 11 (9 to 15) and EQ-5D3L 0.123 (0.035 to 0.222). MID_95%limit estimates were substantially higher than ROC cut-off values and MID_MEAN at all follow-ups for all instruments. The reliable change proportion (RCP) values in the improved group were highest for WOSI and the Rowe Score (ranging from 68 to 87%) and significantly lower for CMS. EQ-5D3L had the lowest values (13 to 16%). We found a moderate correlation between mean change scores of the outcome measures and the anchor, except for the EQ-5D3L.

Conclusions

In patients with SLAP II-lesions the patient reported OISS and WOSI and the clinical Rowe score had best responsiveness. Our results suggest that 3 months follow-up is too early for outcome evaluation.

Standardizing fatigue measurement in multiple sclerosis: the validity, responsiveness and score interpretation of the PROMIS SF v1.0 - Fatigue (MS) 8a

BACKGROUND

Fatigue is one of the most common and the single most disabling symptom of multiple sclerosis (MS). However, there is a lack of consensus on the most appropriate fatigue measures in clinical practice and research, based upon rigorously validated, generalizable, and publicly available instruments. The objective of this research was to generate additional evidence regarding the validity and applicability of the PROMIS SF v1.0 - Fatigue (MS) 8a, including content validity, reliability, construct validity and responsiveness, as well as to assess minimal important difference (MID) estimates and a score interpretation tool to aide meaningful individual level score interpretation.

METHODS

A mixed-methods, sequential design was followed. Cognitive debriefing (CD) interviews (n=29) were performed with MS patients, to assess the relevance and comprehensiveness of the PROMIS Fatigue (MS) 8a scores. To evaluate the psychometric properties of the PROMIS Fatigue (MS) 8a, two observational studies were conducted: a cross-sectional study at two US MS centers (n=296), and a 96-week longitudinal study in a UK MS Register cohort (n=384). Main outcomes and measures were estimates of known-groups validity, convergence validity, reliability, and responsiveness, a guide for interpreting PROMIS Fatigue (MS) 8a T-scores, and anchor-based MID estimates.

RESULTS

The CD interviews confirmed the comprehensiveness and relevance of the PROMIS Fatigue (MS) 8a in assessing MS fatigue. Cronbach's alpha (>0.9) and intra-class correlation coefficient (≥0.9) for test-retest scores at 5-7 days follow-up, supported strong internal consistency and test-retest reliability. Hypothesized differences were found across patient groups in patient reported fatigue and related concepts (analysis of variance [ANOVA], P <0.001). PROMIS Fatigue (MS) 8a scores were sensitive to bi-directional changes in fatigue (GHS fatigue global question) and physical health (PROMIS GHS GPH), over a 52-week follow-up. Score changes of 3.4-4 points are proposed as MID criteria for minimal improvement or worsening in fatigue.

CONCLUSION

This research extends the evidence supporting the content validity and the robust psychometric performance of the PROMIS Fatigue (MS) 8a across US and UK MS populations. Importantly, data supporting the measure's integration in clinical practice and research, including meaningful score interpretation, are now available.

[Minimal important clinical difference in health-related quality of life.]

Una de las limitaciones para el uso de los Cuestionarios de Calidad de Vida Relacionada con la Salud y de los resultados reportados por pacientes es la dificultad de interpretar los valores obtenidos. La diferencia mínima clínica importante es una medida que ayuda a comprender los resultados de estos cuestionarios y valorar la relevancia clínica del efecto conseguido por la intervención realizada. En este trabajo revisamos el concepto de diferencia mínima clínica importante, describimos los métodos utilizados para su obtención y exponemos sus dificultades, limitaciones y aplicabilidad. Dentro de los resultados reportados por pacientes y, particularmente, en los de calidad de vida, la diferencia mínima clínica importante es una herramienta que ayuda a los clínicos a utilizar correctamente las escalas de medida e interpretar el efecto de las intervenciones. Con este artículo esperamos facilitar la implantación y uso de la diferencia mínima clínica importante y los Cuestionarios de Calidad de Vida Relacionada con la Salud en la práctica habitual con nuestros pacientes.

Meaningful values in the Forgotten Joint Score after total knee arthroplasty

AIMS

The aim of this study was to identify the minimal clinically important difference (MCID), minimal important change (MIC), minimal detectable change (MDC), and patient-acceptable symptom state (PASS) threshold in the Forgotten Joint Score (FJS) according to patient satisfaction six months following total knee arthroplasty (TKA).

METHODS

During a one-year period 484 patients underwent a primary TKA and completed preoperative and six-month FJS and OKS. At six months patients were asked, "How satisfied are you with your operated knee?" Their response was recorded as: very satisfied, satisfied, neutral, dissatisfied, or very dissatisfied. The difference between patients recording neutral (n = 44) and satisfied (n = 153) was used to define the MCID. MIC for a cohort was defined as the change in the FJS for those patients declaring their outcome as satisfied, whereas receiver operating characteristic curve analysis was used to determine the MIC for an individual and the PASS threshold. Distribution-based methodology was used to calculate the MDC.

RESULTS

Using satisfaction as the anchor question, the MCID for the FJS was 16.6 (95% confidence interval (CIs) 8.9 to 24.3; p < 0.001) and when adjusting for confounding this decreased to 13.7 points (95% CI 4.8 to 22.5; p < 0.001). The MIC for the FJS for a cohort of patients was 17.7 points and for an individual patient was 10 points. The MDC90 for the FGS was 12 points; where 90% of patients scoring more than this will have experienced a real change that is beyond measurement error. The PASS was defined as 22 points or more in the postoperative FJS.

CONCLUSION

The estimates for MCID and MIC can be used to assess whether there is clinical difference between two groups and whether a cohort/patient has had a meaningful change in their FJS, respectively. The MDC90 of 12 points suggests a value lower than this may fall within measurement error. A postoperative FJS of 22 or more was predictive of achieving PASS. Cite this article: Bone Joint J 2021;103-B(5):846-854.

Identifying the minimal important difference in patient-reported outcome measures in the field of people with severe mental illness: a pre-post-analysis of the Illness Management and Recovery Programme

Purpose

Complementary interventions for persons with severe mental illness (SMI) focus on both personal recovery and illness self-management. This paper aimed to identify the patient-reported outcome measures (PROMs) associated with the most relevant and meaningful change in persons with SMI who attended the Illness Management and Recovery Programme (IMR).

Methods

The effect of the IMR was measured with PROMs concerning recovery, illness self-management, burden of symptoms and quality of life (QoL). From the QoL measures, an anchor was chosen based on the most statistically significant correlations with the PROMs. Then, we estimated the minimal important difference (MID) for all PROMs using an anchor-based method supported by distribution-based methods. The PROM with the highest outcome for effect score divided by MID (the effect/MID index) was considered to be a measure of the most relevant and meaningful change.

Results

All PROMs showed significant pre–post-effects. The QoL measure ‘General Health Perception (Rand-GHP)’ was identified as the anchor. Based on the anchor method, the Mental Health Recovery Measure (MHRM) showed the highest effect/MID index, which was supported by the distribution-based methods. Because of the modifying gender covariate, we stratified the MID calculations. In most MIDs, the MHRM showed the highest effect/MID indexes.

Conclusion

Taking into account the low sample size and the gender covariate, we conclude that the MHRM was capable of showing the most relevant and meaningful change as a result of the IMR in persons with SMI.

Assessing baseline dependency of anchor-based minimal important change (MIC): don't stratify on the baseline score!

PURPOSE

The minimal important change (MIC) of a patient-reported outcome measure (PROM) is often suspected to be baseline dependent, typically in the sense that patients who are in a poorer baseline health condition need greater improvement to qualify as minimally important. Testing MIC baseline dependency is commonly performed by creating two or more subgroups, stratified on the baseline PROM score. This study's purpose was to show that this practice produces biased subgroup MIC estimates resulting in spurious MIC baseline dependency, and to develop alternative methods to evaluate MIC baseline dependency.

METHODS

Datasets with PROM baseline and follow-up scores and transition ratings were simulated with and without MIC baseline dependency. Mean change MICs, ROC-based MICs, predictive MICs, and adjusted MICs were estimated before and after stratification on the baseline score. Three alternative methods were developed and evaluated. The methods were applied in a real data example for illustration.

RESULTS

Baseline stratification resulted in biased subgroup MIC estimates and the false impression of MIC baseline dependency, due to redistribution of measurement error. Two of the alternative methods require a second baseline measurement with the same PROM or another correlated PROM. The third method involves the construction of two parallel tests based on splitting the PROM's item set. Two methods could be applied to the real data.

CONCLUSION

MIC baseline dependency should not be tested in subgroups based on stratification on the baseline PROM score. Instead, one or more of the suggested alternative methods should be used.

Minimal important difference estimates for patient-reported outcomes: A systematic survey

OBJECTIVES

The objective of the study was to develop an inventory summarizing all anchor-based minimal important difference (MID) estimates for patient-reported outcome measures (PROMs) available in the medical literature.

STUDY DESIGN AND SETTING

We searched MEDLINE, EMBASE, CINAHL, PsycINFO, and the Patient-Reported Outcome and Quality of Life Instruments Database internal library (January 1989-October 2018). We included primary studies empirically calculating an anchor-based MID estimate for any PROM in adults and adolescents. Pairs of reviewers independently screened and selected studies, extracted data, and evaluated the credibility of the MIDs.

RESULTS

We identified 585 eligible studies, the majority conducted in Europe (n = 211) and North America (n = 179), reporting 5,324 MID estimates for 526 distinct PROMs. Investigators conducted their studies in the context of patients receiving surgical (n = 105, 18%), pharmacological (n = 85, 15%), rehabilitation (n = 65, 11%), or a combination of interventions (n = 194, 33%). Of all MID estimates, 59% (n = 3,131) used a global rating of change anchor. Major credibility limitations included weak correlation (n = 1,246, 23%) or no information regarding the correlation (n = 3,498, 66%) between the PROM and anchor and imprecision in the MID estimate (n = 2,513, 47%).

CONCLUSION

A large number of MIDs for assisting in the interpretation of PROMs exist. The MID inventory will facilitate the use of MID estimates to inform the interpretation of the magnitude of treatment effects in clinical research and guideline development.

Minimal important difference and patient acceptable symptom state for PFDI-20 and POPDI-6 in POP surgery

Introduction and hypothesis

Patient-reported outcome measures are fundamental tools when assessing effectiveness of treatments. The challenge lies in the interpretation: which magnitude of change in score is meaningful for the patients? The minimal important difference (MID) is defined as the smallest difference in score that patients perceive as important. The Patient Acceptable Symptom State (PASS) represents the value of score beyond which patients consider themselves well. We aimed to determine the MID and PASS for Pelvic Floor Distress Inventory-20 (PFDI-20) and Pelvic Organ Prolapse Distress Inventory-6 (POPDI-6) in pelvic organ prolapse (POP) surgery.

Methods

We used data from 2704 POP surgeries from a prospective, population-based cohort. MID was determined with three anchor-based and one distribution-based method. PASS was defined using two different methods. Medians of the estimates were identified.

Results

The MID estimates with (1) mean change, (2) receiver-operating characteristic (ROC) curve, (3) 75th percentile, and (4) distribution-based method varied between 22.9–25.0 (median 24.2) points for PFDI-20 and 9.0–12.5 (median 11.3) for POPDI-6. The PASS cutoffs with (1) 75th percentile and (2) ROC curve method varied between 57.7–62.5 (median 60.0) for PFDI-20 and 16.7–17.7 (median 17.2) for POPDI-6.

Conclusion

A mean difference of 24 points in the PFDI-20 or 11 points in the POPDI-6 can be used as a clinically relevant difference between groups. Postoperative scores ≤ 60 for PFDI-20 and ≤ 17 for POPDI-6 signify acceptable symptom state.

Minimal important differences for the WOMAC osteoarthritis index and the Forgotten Joint Score-12 in total knee arthroplasty patients

BACKGROUND

Total knee arthroplasty (TKA) is an effective treatment for end-stage osteoarthritis. Patient reported-outcome measures (PROMs) capture the patients' perception of the success of an intervention. The minimal important difference (MID) is an important characteristic of the PROM, which helps to interpret results. The aim of this study was to identify the MID for the Forgotten Joint Score-12 (FJS-12) and Western Ontario and McMaster Universities (WOMAC) osteoarthritis index.

METHODS

Data were collected in a prospective cohort study. Patients were asked to complete the FJS-12, WOMAC osteoarthritis index and transition items evaluating change over time to determine the MID. We employed an anchor-based methodology relating score change to the response categories of the transition items using both binary logistic regression and receiver operating characteristic (ROC) analysis.

RESULTS

Data from 199 patients were analysed. Mean age was 72.3 years, 58% were women. Employing binary logistic regression the MID for the FJS-12 was 10.8 points, for the WOMAC pain score 7.5 points and for the WOMAC function score 7.2 points. ROC analyses found a MID of 13.0 points for the FJS-12, 12.5 points for WOMAC pain and 14.7 points for WOMAC function.

CONCLUSION

We report MIDs for the FJS-12 and the WOMAC Pain and Function scales in a TKA patient cohort, which can be used to interpret meaningful differences in score. In line with previous research, we found more advanced statistical methods to result in smaller MID estimates for both scores.

TRIAL REGISTRATION

Written consent for this study was obtained from all participants and ethical approval was granted by the local ethics committee (Ethikkommission St. Gallen; EKSG 14/973; Registered 03 July 2014; http://www.sg.ch/home/gesundheit/ethikkommission.html).

Practical issues encountered while determining Minimal Clinically Important Difference in Patient-Reported Outcomes

Background

Using a real dataset, we highlighted several major methodological issues raised by the estimation of the Minimal Clinically Important Difference (MCID) of a Patient-Reported Outcomes instrument. We especially considered the management of missing data and the use of more than two times of measurement. While inappropriate missing data management and inappropriate use of multiple time points can lead to loss of precision and/or bias in MCID estimation, these issues are almost never dealt with and require cautious considerations in the context of MCID estimation.

Methods

We used the LIGALONGO study (French Randomized Controlled Trial). We estimated MCID on the SF-36 General Health score by comparing many methods (distribution or anchor-based). Different techniques for imputation of missing data were performed (simple and multiple imputations). We also consider all measurement occasions by longitudinal modeling, and the dependence of the score difference on baseline.

Results

Three hundred ninety-three patients were studied. With distribution-based methods, a great variability in MCID was observed (from 3 to 26 points for improvement). Only 0.2 SD and 1/3 SD distribution methods gave MCID values consistent with anchor-based methods (from 4 to 7 points for improvement). The choice of missing data imputation technique clearly had an impact on MCID estimates. Simple imputation by mean score seemed to lead to out-of-range estimate, but as missing not at random mechanism can be hypothesized, even multiple imputations techniques can have led to an slight underestimation of MCID. Using 3 measurement occasions for improvement led to an increase in precision but lowered estimates.

Conclusion

This practical example illustrates the substantial impact of some methodological issues that are usually never dealt with for MCID estimation. Simulation studies are needed to investigate those issues.

Trial registration

NCT01240772 (ClinicalTrials.gov) registered on November 15, 2010.

Update on the psychometric properties and minimal important difference (MID) thresholds of the FACT-M questionnaire for use in treatment-naïve and previously treated patients with metastatic Merkel cell carcinoma

OBJECTIVES

For valid and reliable assessment of patients' Health-Related Quality of Life (HRQoL), it is crucial to use psychometrically robust instruments. In the context of rare diseases such as Merkel cell carcinoma (MCC), validated disease-specific instruments are often not available. The Functional Assessment of Cancer Therapy - Melanoma (FACT-M) was originally developed for use in melanoma. Its psychometric performance for use in MCC and minimal important difference (MID) thresholds have been previously reported based on a cohort of metastatic MCC patients who had disease progression following one or more prior line of chemotherapy (NCT02155647 Part A; n = 70). Since then, new data from the phase II JAVELIN Merkel 200 trial among treatment-naïve patients are available (NCT02155647 Part B; n = 102). This study aims to increase accuracy and precision of previously established psychometric properties and MID thresholds of FACT-M in metastatic MCC patients.

METHODS

Published qualitative research suggests that patients with metastatic MCC had similar experiences and described similar concepts associated with their disease independent of whether they were treatment naïve or had prior treatment. Therefore, it was deemed appropriate to pool FACT-M data from Part A (previously treated) and Part B (treatment-naïve) cohorts for this study. Construct validity was assessed by evaluating item-factor correlations (convergent validity) and known-groups validity using ECOG performance status 0 versus 1. Concurrent validity was assessed using EQ-5D items. Internal consistency reliability was assessed using Cronbach's α. Anchor- and distribution-based approaches were used to derive MID thresholds.

RESULTS

Overall, psychometric tests based on various validity (convergent, known-groups, concurrent) and reliability (Cronbach α) analyses confirmed previous findings in that FACT-M performs well in MCC patients. MID thresholds derived from this study are largely in line with previously established thresholds with some minor adjustments.

CONCLUSIONS

In the context of rare diseases, which often have limited data available for psychometric testing, a reasonably large MCC patient sample was available for this study, enhancing accuracy and precision of previously established FACT-M psychometric properties and MID thresholds with only small deviations for use in metastatic MCC patients. Results suggest that the FACT-M is suitable for Merkel cell carcinoma regardless of patients' treatment status.

TRIAL REGISTRATION

This study is a pre-planned post-hoc analysis conducted on data collected in Part A and Part B of the JAVELIN Merkel 200 trial. This trial was registered on 2 June 2014 with ClinicalTrials.gov as NCT02155647.

Minimal important change in physical function in trauma patients: a study using the short musculoskeletal function assessment

Purpose

The Short Musculoskeletal Function Assessment (SMFA) questionnaire can be used to evaluate physical functioning in patients with traumatic injuries. It is not known what change in score reflects a meaningful change to patients. The aim was to determine minimal important change (MIC) values of the subscales (0–100) of the Dutch SMFA-NL in a sample of patients with a broad range of injuries.

Methods

Patients between 18 and 65 years of age completed the SMFA-NL and the Global Rating of Effect (GRE) questions at 6-week and 12-month post-injury. Anchor-based MIC values were calculated using univariable logistic regression analyses.

Results

A total of 225 patients were included (response rate 67%). The MIC value of the Upper Extremity Dysfunction (UED) subscale was 8 points, with a misclassification rate of 43%. The Lower Extremity Dysfunction subscale MIC value was 14 points, with a misclassification rate of 29%. The MIC value of the Problems with Daily Activities subscale was 25 points, with a misclassification rate of 33%. The MIC value of the Mental and Emotional Problems (MEP) subscale was 7 points, with a misclassification rate 37%.

Conclusion

MIC values of the SMFA-NL were determined. The MIC values aid interpreting whether a change in physical functioning can be considered clinically important. Due to the considerable rates of misclassification, the MIC values of the UED and MEP subscales should be used with caution.

Clinical thresholds of symptoms for deciding on surgery for trapeziometacarpal osteoarthritis

The severity of preoperative symptoms at which patients are likely to achieve a minimal important change and patient acceptable symptom state after surgery may help the decision to perform surgery for trapeziometacarpal osteoarthritis. The study objective was to define these thresholds for pain at rest and during activities as well as for the brief Michigan Hand Outcomes Questionnaire. One hundred and fifty-one patients were examined before surgery and 3, 6 and 12 months after surgery. The minimal important change after surgery was 1.9, 3.9 and 16 scores for pain at rest, pain during activities and the brief Michigan Hand Outcomes Questionnaire, respectively. The respective patient acceptable symptom state values were 1.5, 2.5 and 70 after surgery. Our results show that patients with baseline pain values between 3.5 and 5.5 at rest, between 6.5 and 7.5 during activities and a presurgery brief Michigan Hand Outcomes Questionnaire score of about 47, have the greatest chance of achieving a relevant symptom change and an acceptable symptom state. The information from this study may help surgeons in deciding the surgical indications and help patients in their expectation in symptom relief after surgery. Level of evidence: IV.

Measuring Clinical Treatment Response in Myasthenia Gravis

In this article we provide an overview of health-related outcome measurement-to better understand what different outcomes used in myasthenia actually measure-and to provide some guidance when choosing measures based on the clinical context and question. In myasthenia, the most commonly used outcome measures are aimed at assessing the signs and symptoms. In this review, we provide a summary of the most commonly used outcome measures. We discuss instruments that gauge disease overall health impact, such as on disability and quality of life. Finally, we discuss other relevant outcomes such as steroid-sparing effects and the role of surrogate markers.

Evaluating minimal important differences and responder definitions for the asthma symptom diary in patients with moderate to severe asthma

Background

The Asthma Symptom Diary was developed to assess severity of symptoms in patients with moderate to severe asthma, and has evidence supporting reliability and validity. Only limited information is available on sensitivity to change and responder definitions for the Asthma Symptom Diary.

Objectives

Main study objectives were to evaluate sensitivity to change and provide responder definitions for clinically meaningful effects for the Asthma Symptom Diary.

Methods

This is a secondary analysis of Phase II clinical trial data in patients with moderate to severe asthma, Asthma Symptom Diary (ASD) was collected daily during the 24-week study. The Asthma Control Questionnaire and the Patient Global Assessment were collected at baseline, and week 12 and 24. Analysis of covariance (ANCOVA) models were used to evaluate sensitivity to change in Asthma Symptom Diary scores after 12 and 24 weeks of treatment. Anchor-based methods, using Asthma Control Questionnaire and Patient Global Assessment defined anchors, were used to identify minimal important differences and various responder criteria for changes in mean 7-day ASD score, symptomatic days, and minimal symptom days.

Results

Sample was 59% female, 81% White, with a mean age of 47.3 (SD = 13.6) years. ANCOVAs demonstrated significant differences in baseline to week 12 and week 24 changes in mean 7-day Asthma Symptom Diary scores and symptomatic days by Asthma Control Questionnaire (all p < 0.001) and Patient Global Assessment anchors (all p < 0.001). Meaningful responders, from the patient’s perspective, were defined as improvements of 0.5–0.6 points (SD = 0.6; scale range 0 to 4) in mean 7-day Asthma Symptom Diary scores, and as a reduction of 2 to 3 Asthma Symptom Diary-based symptomatic days.

Conclusion

The Asthma Symptom Diary was responsive to changes in clinical status in patients with moderate to severe asthma. Responder definitions were identified, including symptomatic days, for evaluating individual level treatment effects in clinical trials.

The minimal important difference of the Australian Pelvic Floor Questionnaire

INTRODUCTION AND HYPOTHESIS

The aim of this study was to establish the minimal important difference (MID) of the Australian Pelvic Floor Questionnaire (APFQ) in women undergoing surgery for stress urinary incontinence or symptomatic pelvic organ prolapse. A further aim was to estimate dysfunction scores dependent on the bothersomeness in a community cohort.

METHODS

The APFQ was completed before and 6 weeks after pelvic floor surgery by 183 women (n = 80 suburethral tape insertion; n = 103 laparoscopic sacrocolpopexy). Distribution and anchor-based methods were used to establish the effect size, standardised response mean and MID (calculated as the difference between women who stated no change or a little better in the Patient Global Impression of Improvement [PGI-I]). In a community cohort of 470 women aged 42-80 years, the APFQ was analysed according to disclosed bothersomeness.

RESULTS

For the suburethral tape group, the effect size in the bladder domain was 1.5 and the PGI-I-based MID 1.3. For the POP surgery, group the effect size in the prolapse domain was calculated at 2.2 and the PGI-I-based MID at 1.0. The domain scores for women who declared no bother were significantly different from those who were a little bothered (bladder domain 2.2 vs 4.0, bowel 0.6 vs 1.7, POP 0.1 vs 3.2, sex 1.8 vs 3.0) with wide variations.

CONCLUSIONS

The MID of the APFQ ranged from 1.0 to 1.3 in the domains after POP or continence surgery respectively. This is corroborated by the differences in domain scores from community-based women who were bothered versus not bothered by pelvic floor symptoms.

The interpretation of change score of the pain disability index after vocational rehabilitation is baseline dependent

Background

The Pain Disability Index (PDI) is a widely-used instrument to measure pain-related disability. The aim of this study was to assess the responsiveness and interpretation of change score of the PDI in patients with chronic musculoskeletal pain (CMP) at discharge of vocational rehabilitation.

Methods

Retrospective data of patients with CMP who attended vocational rehabilitation between 2014 and 2017 was used. The anchor-based method was used to assess the responsiveness of the total sample and of PDI baseline quartile groups. A receiver operating characteristic curve was performed, including Area Under the Curve (AUC) and Minimal Important Change (MIC).

Results

The PDI showed responsive to detect clinically relevant changes in pain-related disability at discharge of vocational rehabilitation (AUC 0.79). A PDI change score of 13 points (MIC 12.5) can be considered as a real change in pain-related disability for the total study sample, and a PDI change score of 7–20 points can be considered as a real change in pain-related disability for PDI lowest and highest baseline quartile scores.

Conclusion

The PDI is responsive in patients with CMP at discharge of vocational rehabilitation. The interpretation of change score depends on PDI baseline score. Patients with a PDI baseline score of ≤27 should decrease minimal 7 points, patients with a baseline score between 28 and 42 should decrease minimal 15 points, and patients with a baseline score ≥ 43 should decrease minimal 20 points.

The minimal important difference of the Australian Pelvic Floor Questionnaire

INTRODUCTION AND HYPOTHESIS

The aim of this study was to establish the minimal important difference (MID) of the Australian Pelvic Floor Questionnaire (APFQ) in women undergoing surgery for stress urinary incontinence or symptomatic pelvic organ prolapse. A further aim was to estimate dysfunction scores dependent on the bothersomeness in a community cohort.

METHODS

The APFQ was completed before and 6 weeks after pelvic floor surgery by 183 women (n = 80 suburethral tape insertion; n = 103 laparoscopic sacrocolpopexy). Distribution and anchor-based methods were used to establish the effect size, standardised response mean and MID (calculated as the difference between women who stated no change or a little better in the Patient Global Impression of Improvement [PGI-I]). In a community cohort of 470 women aged 42-80 years, the APFQ was analysed according to disclosed bothersomeness.

RESULTS

For the suburethral tape group, the effect size in the bladder domain was 1.5 and the PGI-I-based MID 1.3. For the POP surgery, group the effect size in the prolapse domain was calculated at 2.2 and the PGI-I-based MID at 1.0. The domain scores for women who declared no bother were significantly different from those who were a little bothered (bladder domain 2.2 vs 4.0, bowel 0.6 vs 1.7, POP 0.1 vs 3.2, sex 1.8 vs 3.0) with wide variations.

CONCLUSIONS

The MID of the APFQ ranged from 1.0 to 1.3 in the domains after POP or continence surgery respectively. This is corroborated by the differences in domain scores from community-based women who were bothered versus not bothered by pelvic floor symptoms.

Principles of Statistics: What the Sports Medicine Professional Needs to Know

Understanding the results and statistics reported in original research remains a large challenge for many sports medicine practitioners and, in turn, may be among one of the biggest barriers to integrating research into sports medicine practice. The purpose of this article is to provide minimal essentials a sports medicine practitioner needs to know about interpreting statistics and research results to facilitate the incorporation of the latest evidence into practice. Topics covered include the difference between statistical significance and clinical meaningfulness; effect sizes and confidence intervals; reliability statistics, including the minimal detectable difference and minimal important difference; and statistical power.

Brief communication: use of the minimal important difference for a meta-analysis on exercise and anxiety in adults with arthritis

A recent meta-analysis reported statistically significant improvements in anxiety as a result of exercise in adults with arthritis and other rheumatic diseases (AORD) using the traditional standardized mean difference (SMD) effect size (ES). The objective of this study was to use the more recently developed and clinically relevant minimal important difference (MID) approach to examine this association. Data from a previous meta-analysis of 14 randomized controlled trials representing 926 initially enrolled adults ≥ 18 years of age (539 exercise, 387 control) was used to calculate the ES using the MID approach. Minimal important difference data were derived from previously reported anchor-based values that represented the different instruments used to assess anxiety. Effect sizes were pooled using the inverse heterogeneity (IVhet) model. Overall, exercise resulted in a mean ES reduction in anxiety of - 0.80 (95% CI, - 1.60 to 0.001, p = 0.05; Q = 92.1, p < 0.001, I ²  = 83.7%, 95% CI, 74.9%, 89.5%), suggesting that overall, exercise may benefit an appreciable number of patients. Nonetheless, this effect spanned the range from many patients gaining important benefits to no patients improving. The clinically relevant effects of exercise on anxiety in adults with AORD are varied. However, these results should be interpreted with caution given the absence of anchor-based MID data specific to the instruments and questions used to assess anxiety in adults with AORD. A need exists for future research to establish instrument-specific, anchor-based MID values for questions assessing anxiety in adults with AORD.

Minimal clinically important difference for pain on the VAS scale and the relation to quality of life in women with endometriosis

OBJECTIVES

The minimal important difference can be helpful in interpreting data from clinical trials. The objective of the study was to calculate the minimal important difference for improvement on the VAS scale for women with endometriosis.

STUDY DESIGN

A prospective study was conducted to evaluate the effect of pertubation with lignocaine on dysmenorrhea and quality of life in women with endometriosis. Data collected in the trial were used for additional analyses in the present descriptive study. Eligible women (n=37) had endometriosis with pain>VAS 50mm (visual analogue scale).

MAIN OUTCOME MEASURES

In a questionnaire, women evaluated their maximum pain on the VAS- scale during every menstrual period before and after treatment. They also estimated the changes in overall pain level by answering the response categories "much better", "somewhat better", "about the same", "somewhat worse" or "much worse". The women were grouped according to their own estimation of change in pain intensity after four months. The minimal important differences for change on the VAS scale correlate to the mean change for women who felt "somewhat better" (n=18) excluding those who were pain free (n=2).

RESULTS

The minimal important difference for improvement on the VAS scale was found to be -39mm and/or -49%.

CONCLUSION

If the patients have a pain level of at least 50mm on VAS scale at inclusion, the cut off for success in clinical trials is suggested to be defined as an either >40mm or a >50% decrease on VAS scale. Trial registry ClinicalTrials.gov Identifier: NCT01329796.

Biological variation of extracellular matrix biomarkers in patients with stable chronic heart failure

BACKGROUND

Extracellular matrix (ECM) biomarkers such as matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) are pathophysiological key, prognostic marker and therapeutic target in chronic heart failure (HF). Serial measurements of MMPs and TIMPs may be useful for guidance of these applications. However, interpretation of time-dependent changes requires knowledge about the biological variation of ECM biomarkers.

METHODS

We performed measurements of MMP-2, MMP-9, TIMP-1, and TIMP-4 in 50 patients with chronic HF who met rigid criteria for clinical stability at 3-h, 6-h, 1-week and 2-week time intervals. In addition, clinical and haemodynamic assessment was performed at baseline, at 1- and 2-week intervals. Haemodynamic variables were measured using inert gas rebreathing and impedance cardiography. Heart rhythm was monitored with external ECG event recorders throughout the complete study. Reference change values (RCVs) and minimal important differences (MIDs) were determined for MMP-2, MMP-9, TIMP-1, and TIMP-4.

RESULTS

Clinical and haemodynamic variables were stable over time. Depending on the time-interval, RCVs ranged between 4.9 and 11.7% for MMP-2, 26.4 and 56.7% for MMP-9, 10.8 and 30.7% for TIMP-1, and 16.0 and 47.4% for TIMP-4, respectively. The MIDs varied between 43.38 and 65.22 ng/ml for MMP-2, 28.71 and 40.96 ng/ml for MMP-9, 52.32 and 156.07 ng/ml for TIMP-1, and 293.92 and 798.04 pg/ml for TIMP-4, respectively.

CONCLUSION

The biological variation of ECM biomarkers differs with respect to individual biomarkers and time intervals. MMP-2 may be most suitable for serial biomarker measurements, as the biological variation is low irrespective of the time interval between measurements.

Impact of the occurrence of a response shift on the determination of the minimal important difference in a health-related quality of life score over time

Background

An important challenge of the longitudinal analysis of health-related quality of life (HRQOL) is the potential occurrence of a Response Shift (RS) effect. While the impact of RS effect on the longitudinal analysis of HRQOL has already been studied, few studies have been conducted on its impact on the determination of the Minimal Important Difference (MID). This study aims to investigate the impact of the RS effect on the determination of the MID over time for each scale of both EORTC QLQ-C30 and QLQ-BR23 questionnaires in breast cancer patients.

Methods

Patients with breast cancer completed the EORTC QLQ-C30 and the EORTC QLQ-BR23 questionnaires at baseline (time of diagnosis; T0), three months (T1) and six months after surgery (T2). Four hospitals and care centers participated in this study: cancer centers of Dijon and Nancy, the university hospitals of Reims and Strasbourg At T1 and T2, patients were asked to evaluate their HRQOL change during the last 3 months using the Jaeschke transition question. They were also asked to assess retrospectively their HRQOL level of three months ago.

The occurrence of the RS effect was explored using the then-test method and its impact on the determination of the MID by using the Anchor-based method.

Results

Between February 2006 and February 2008, 381 patients were included of mean age 58 years old (SD = 11). For patients who reported a deterioration of their HRQOL level at each follow-up, an increase of RS effect has been detected between T1 and T2 in 13/15 dimensions of QLQ-C30 questionnaire, and 4/7 dimensions of QLQ-BR23 questionnaire. In contrast, a decrease of the RS effect was observed in 8/15 dimensions of QLQ-C30 questionnaire and in 5/7 dimensions of QLQ-BR23 questionnaire in case of improvement. At T2, the MID became ≥ 5 points when taking into account the RS effect in 10/15 dimensions of QLQ-C30 questionnaire and in 5/7 dimensions of QLQ-BR23 questionnaire.

Conclusions

This study highlights that the RS effect increases over time in case of deterioration and decreases in case of improvement. Moreover, taking the RS into account produces a reliable and significant MID.

Electronic supplementary material

The online version of this article (doi:10.1186/s12955-016-0569-5) contains supplementary material, which is available to authorized users.

Meta-analysis on continuous outcomes in minimal important difference units: an application with appropriate variance calculations

OBJECTIVE

To compare results from meta-analyses for mean differences in minimal important difference (MID) units (MD_MID), when MID is treated as a random variable vs. a constant.

STUDY DESIGN AND SETTING

Meta-analyses of published data. We calculated the variance of MD_MID as a random variable using the delta method and as a constant. We assessed performance under different assumptions. We compare meta-analysis results from data originally used to present the MD_MID and data from osteoarthritis studies using different domain instruments.

RESULTS

Depending on the data set and depending on the values of rho and coefficient of variation of the MID (CoV_MID), estimates of treatment effect and P-values between an approach considering the MID as a constant vs. as a random variable may differ appreciably. Using our data sets, we provide examples of the potential magnitude. When rho = 0.5 and CoV_MID = 0.8, considering MID as a constant overestimated the treatment effect by 33-110% and decreased the P-value for heterogeneity from above 0.95 to below 0.08. When rho = 0.8 and CoV_MID = 0.5, the magnitude of the effects was similar.

CONCLUSIONS

Considering MID as a random variable avoids unrealistic assumptions and provides more appropriate treatment effect estimates.

Limited responsiveness related to the minimal important difference of patient-reported outcomes in rare diseases

OBJECTIVES

To explore the responsiveness of patient-reported outcomes (PROs) in interventional studies involving patients with rare lysosomal storage diseases (LSDs).

STUDY DESIGN AND SETTING

We searched eight databases for experimental and nonexperimental studies. Pairs of trained reviewers independently screened articles and subsequently extracted data from the eligible studies. Among studies with 10 or more patients using a valid PRO, we assessed the responsiveness of PROs based on a reanalysis of the data using minimal important difference estimates. Our analyses focused on statistically significant within-group differences in PROs for observational studies or the statistically significant between-group differences in PRO scores for controlled studies.

RESULTS

Of 2,679 unique records, 62 interventional studies addressing patients with Fabry (55%), Gaucher (19%), Pompe (16%), and mucopolysaccharidoses (11%) proved eligible. The most frequently used PROs were the Short-Form-36 (25 studies), Brief Pain Inventory (20 studies), EuroQoL-5D (9 studies), and the Fatigue Severity Scale (6 studies). Observational studies suggest that PROs sometimes detect significant within-group changes when present. Randomized trials raise questions regarding the responsiveness of PROs to small differences between groups.

CONCLUSIONS

Most studies have relied on generic PROs to evaluate quality of life and symptoms in patients with rare LSDs. PROs appear more responsive in observational studies than randomized trials.

Minimal important differences for fatigue patient reported outcome measures-a systematic review

BACKGROUND

Fatigue is the most frequent symptom reported by patients with chronic illnesses. As a subjective experience, fatigue is commonly assessed with patient-reported outcome measures (PROMs). Currently, there are more than 40 generic and disease-specific PROMs for assessing fatigue in use today. The interpretation of changes in PROM scores may be enhanced by estimates of the so-called minimal important difference (MID). MIDs are not fixed attributes of PROMs but rather vary in relation to estimation method, clinical and demographic characteristics of the study group, etc. The purpose of this paper is to compile published MIDs for fatigue PROMs, spanning diagnostic/patient groups and estimation methods, and to provide information relevant for appraising their appropriateness for use in specific clinical trials and in monitoring fatigue in defined patient groups in routine clinical practice.

METHODS

A systematic search of three databases (Scopus, CINAHL and Cochrane) for studies published between January 2000 to April 2015 using fatigue and variations of the term MID, e.g. MCID, MIC, etc. Two authors screened search hits and extracted data independently. Data regarding MIDs, anchors used and study designs were compiled in tables.

RESULTS

Included studies (n = 41) reported 60 studies or substudies estimating MID for 28 fatigue scales, subscales or single item measures in a variety of diagnostic groups and study designs. All studies used anchor-based methods, 21/60 measures also included distribution-based methods and 17/60 used triangulation of methods. Both similarities and dissimilarities were seen within the MIDs.

CONCLUSIONS

Magnitudes of published MIDs for fatigue PROMs vary considerably. Information about the derivation of fatigue MIDs is needed to evaluate their applicability and suitability for use in clinical practice and research.

Communicating statin evidence to support shared decision-making

BACKGROUND

The practice of clinical medicine rests on a foundation of ethical principles as well as scientific knowledge. Clinicians must artfully balance the principle of beneficence, doing what is best for patients, with autonomy, allowing patients to make their own well-informed health care decisions. The clinical communication process is complicated by varying degrees of confidence in scientific evidence regarding patient-oriented benefits, and by the fact that most medical options are associated with possible harms as well as potential benefits.

DISCUSSION

Evidence-based clinical guidelines often neglect patient-oriented issues involved with the thoughtful practice of shared decision-making, where individual values, goals, and preferences should be prioritized. Guidelines on the use of statin medications for preventing cardiovascular events are a case in point. Current guidelines endorse the use of statins for people whose 10-year risk of cardiovascular events is as low as 7.5%. Previous guidelines set the 10-year risk benchmark at 20%. Meta-analysis of randomized trials suggests that statins can reduce cardiovascular event rates by about 25%, bringing 10-year risk from 7.5 to 5.6%, for example, or from 20 to 15%. Whether or not these benefits should justify the use of statins for individual patients depends on how those advantages are valued in comparison with disadvantages, such as side effect risks, and with inconveniences associated with taking a pill each day and visiting clinicians and laboratories regularly.

CONCLUSIONS

Whether or not the overall benefit-harm balance justifies the use of a medication for an individual patient cannot be determined by a guidelines committee, a health care system, or even the attending physician. Instead, it is the individual patient who has a fundamental right to decide whether or not taking a drug is worthwhile. Researchers and professional organizations should endeavor to develop shared decision-making tools that provide up-to-date best evidence in easily understandable formats, so as to assist clinicians in helping their patients to make the decisions that are right for them.

The effect of the patient-physician relationship on health-related quality of life after cardiac rehabilitation

Purpose The patient-physician relationship has effects on adherence and health outcomes in chronic diseases. This prospective study investigates the effect of the patient-physician relationship on patients' health-related quality of life (HRQOL) in the context of cardiac rehabilitation. Methods Three hundred and thirty-eight German patients filled out questionnaires at the start and end of rehabilitation and at 6 months follow-up. Patient-physician relationship variables surveyed were patient involvement (perceived involvement in care scales), trust in the physician, patient satisfaction (PHYSAT) and physician's communicative behaviour (KOVA). After adjusting for multiple confounders, hierarchical regression analyses were conducted to predict the influence of the patient-physician relationship on HRQOL after rehabilitation. We further examined clinical relevance using minimal clinically important differences (MCID). Results In the hierarchical regression analyses, 42.8-54.9% of the variance at the end of rehabilitation and 22.4-40.5% at follow-up were explained. The patient-physician variables patient satisfaction, physician's emotionally supportive communication and effective and open communication accounted for 1.4-2.6% of the variance and proved statistically and clinically significant for HRQOL change. Further predictors for better HRQOL were higher income and less trait anger. Conclusion Aspects of the patient-physician relationship are significant predictors for patients' HRQOL after rehabilitation. Rehabilitation physicians should emotionally support the patients and communicate in an effective and open manner to enhance HRQOL. Implications for rehabilitation Aspects of the patient-physician relationship have effects on adherence and clinical outcomes in chronic diseases. In this cardiac sample, the patient-physician relationship had an influence on patients' health-related quality of life (HRQOL) after inpatient rehabilitation. Rehabilitation physicians should emotionally support and encourage the patients and communicate with them in an effective and open manner to enhance patients' HRQOL.

Distribution-based estimates of minimal important difference for hospital anxiety and depression scale and impact of event scale-revised in survivors of acute respiratory failure

OBJECTIVE

This study will estimate distribution-based minimal important difference (MID) for the Hospital Anxiety and Depression Scale anxiety (HADS-A) and depression (HADS-D) subscales, and the Impact of Event Scale-Revised (IES-R) in survivors of acute respiratory failure (ARF).

METHODS

Secondary analyses of data from two US and three UK studies of ARF survivors (total N=1223). HADS-D and HADS-A were used to assess depression and anxiety symptoms. IES-R assessed post-traumatic stress disorder symptoms. Standard error of measurement, minimal detectable change90, 0.5 standard deviation (S.D.), and 0.2 S.D. were used to estimate MID for the combined sample, by studies, 6- and 12-month follow-ups, country and mental health condition.

RESULTS

Overall, MID estimates converged to 2.0-2.5 for the HADS-A, 1.9-2.3 for the HADS-D and 0.17-0.18 for the IES-R. MID estimates were comparable across studies, follow-up, country and mental health condition.

CONCLUSION

Among ARF survivors, 2.0-2.5 is a reasonable range for the MID for both HADS subscales, and 0.2 is reasonable for IES-R. Until anchor-based MIDs for these instruments are available, these distribution-based estimates can help researchers plan future studies and interpret the clinical importance of findings in ARF patient populations.

Biological variation, reference change value (RCV) and minimal important difference (MID) of inspiratory muscle strength (PImax) in patients with stable chronic heart failure

BACKGROUND

Despite the widespread application of measurements of respiratory muscle force (PImax) in clinical trials there is no data on biological variation, reference change value (RCV), or the minimal important difference (MID) for PImax irrespective of the target cohort. We addressed this issue for patients with chronic stable heart failure.

METHODS AND RESULTS

From the outpatients' clinic of the University of Heidelberg we retrospectively selected three groups of patients with stable systolic chronic heart failure (CHF). Each group had two measurements of PImax: 90 days apart in Group A (n = 25), 180 days apart in Group B (n = 93), and 365 days apart in Group C (n = 184). Stability was defined as (a) no change in NYHA class between visits and (b) absence of cardiac decompensation 3 months prior, during, and 3 months after measurements. For each group, we determined within-subject (CVI), between-subject (CVG), and total (CVT) coefficient of variation (CV), the index of individuality (II), RCV, reliability coefficient, and MID of PImax. CVT was 8.7, 7.5, and 6.9 % for groups A, B, and C, respectively. The II and RCV were 0.21, 0.20, 0.16 and 13.6, 11.6, 10.8 %, respectively. The reliability coefficient and MID were 0.83, 0.87, 0.88 and 1.44, 1.06, 1.12 kPa, respectively. Results were similar between age, gender, and aetiology subgroups.

CONCLUSION

In patients with stable CHF, measurements of PImax are highly stable for intervals up to 1 year. The low values for II suggest that evaluation of change in PImax should be performed on an individual (per patient) basis. Individually significant change can be assumed beyond 14 % (RCV) or 1.12 kPa (MID).

Meaningful changes for the Oxford hip and knee scores after joint replacement surgery

Objectives

To present estimates of clinically meaningful or minimal important changes for the Oxford Hip Score (OHS) and the Oxford Knee Score (OKS) after joint replacement surgery.

Study Design and Setting

Secondary data analysis of the NHS patient-reported outcome measures data set that included 82,415 patients listed for hip replacement surgery and 94,015 patients listed for knee replacement surgery was performed.

Results

Anchor-based methods revealed that meaningful change indices at the group level [minimal important change (MIC)], for example in cohort studies, were ∼11 points for the OHS and ∼9 points for the OKS. For assessment of individual patients, receiver operating characteristic analysis produced MICs of 8 and 7 points for OHS and OKS, respectively. Additionally, the between group minimal important difference (MID), which allows the estimation of a clinically relevant difference in change scores from baseline when comparing two groups, that is, for clinical trials, was estimated to be ∼5 points for both the OKS and the OHS. The distribution-based minimal detectable change (MDC₉₀) estimates for the OKS and OHS were 4 and 5 points, respectively.

Conclusion

This study has produced and discussed estimates of minimal important change/difference for the OKS/OHS. These estimates should be used in the power calculations and the interpretation of studies using the OKS and OHS. The MDC₉₀ (∼4 points OKS and ∼5 points OHS) represents the smallest possible detectable change for each of these instruments, thus indicating that any lower value would fall within measurement error.

Minimal important difference in field walking tests in non-cystic fibrosis bronchiectasis following exercise training

BACKGROUND

The 6-min walk distance (6MWD) and incremental shuttle walk distance (ISWD) are clinically meaningful measures of exercise capacity in people with non-cystic fibrosis (CF) bronchiectasis, but the change in walking distance which constitutes clinical benefit is undefined. This study aimed to determine the minimal important difference for the 6MWD and ISWD in non-CF bronchiectasis.

METHODS

Thirty-seven participants with mean FEV1 70% predicted completed both field walking tests before and after an 8-week exercise program. The minimal important difference was calculated using a distribution-based and anchor-based method, with the global rating of change scale used.

RESULTS

The mean change in 6MWD in participants who reported themselves to be unchanged was 10 m, compared to 36 m (small change) and 45 m (substantial change) (p = 0.01). For the ISWD, the mean change in participants who reported themselves to be unchanged was 33 m, compared to 54 m (small change) and 73 m (substantial change) (p = 0.04). The anchor-based method defined the minimal important difference for 6MWD as 24.5 m (AUC 0.76, 95% CI 0.61-0.91) and for ISWD as 35 m (AUC 0.88, 95% CI 0.73-0.99), based on participant's global rating of change. The distribution-based method indicated a value of 22.3 m for the 6MWD and 37 m for the ISWD. There was excellent agreement between the two methods for the 6MWD (kappa = 0.91) and the ISWD (kappa = 0.92).

CONCLUSIONS

Small changes in 6MWD and ISWD may represent clinically important benefits in people with non-CF bronchiectasis. These data are likely to assist in the interpretation of change in exercise capacity following intervention.