Discrimination of changes in osteoporosis outcomes

The purpose of this paper was to identify existing work related to discrimination, responsiveness, and minimal clinically important differences (MCID) for 4 key clinical outcomes in osteoporosis, to serve as a background to discussions about how to define MCID for both individuals and groups. The outcomes assessed were bone density, fractures, quality of life, and function. We conducted a systematic literature search in MEDLINE, EMBASE, and Current Contents for articles that discussed responsiveness, detectable difference, improvement criteria, and clinical importance. We used the Beaton cube to classify the studies depending on whether they compared differences between or changes within individuals or groups. Although a number of studies were identified that presented data on detectable differences beyond error and observed differences, few studies presented data on how to define clinically important differences. A key priority for future research is to define minimally clinical important differences for clinically important osteoporosis outcomes using a consensus based approach that will be accepted by the osteoporosis community at large. Furthermore, these MCID will likely be different for individual patients seen in clinical practice than for individuals in a clinical trial.     

Minimal clinically important difference for the UCSD Shortness of Breath Questionnaire

PURPOSE: A minimal clinically important difference (MCID) is important in evaluating clinical measures such as health-related quality of life (HRQOL) instruments. The purpose of this analysis is to evaluate MCID for the UCSD Shortness of Breath Questionnaire (SOBQ). METHODS: We examined measures of disease-specific and generic HRQOL in 164 subjects with chronic lung disease before and after pulmonary rehabilitation. Subjects completed 2 disease-specific [SOBQ, Chronic Respiratory Questionnaire (CRQ)], and 2 generic HRQOL measures [RAND-36 and Quality of Well-Being Scale (QWB)]. The MCID was calculated using 3 methods: effect size, standard error of the measurement (SEM), and comparison between the SOBQ and CRQ Dyspnea scores. RESULTS: HRQOL measures correlated moderately with measures of maximum exercise tolerance but not with lung function (FEV1, FVC). HRQOL and exercise capacity improved significantly after pulmonary rehabilitation. A change of 5 units for the SOBQ appears to be a reasonable MCID for this instrument. The calculated MCIDs for the CRQ (0.47/item) and QWB (0.031) were consistent with established change scores. CONCLUSIONS: The MCID calculated using an SEM approach for the SOBQ, CRQ, and QWB meets clinical expectations for these instruments. HRQOL measures provide information that is complementary and distinct from physiological measures.     

The MCID of the transition dyspnea index is a total score of one unit

The Baseline (BDI) and Transition (TDI) Dyspnea Indexes provide interview-based measurements of breathlessness related to activities of daily living. The BDI is a discriminative instrument that includes specific criteria for each of three components at a single point in time. The TDI is an evaluative instrument that includes specific criteria for each of three components to measure changes from a baseline state. Observational studies have shown that patients with COPD generally experience a gradual progression of breathing difficulty as measured by the TDI over time. Randomized controlled trials have demonstrated excellent measurement characteristics of the TDI; these include responsiveness (ability to detect change) and construct validity (a change in the TDI correlates with changes in other variables). Supporting evidence for one unit as the minimal clinically important difference (MCID) of the TDI is based on: expert preference; use of the physician's global evaluation score as an anchor; and distribution estimates (standard error of measurement and 0.5 of the standard deviation). As an alternative to the interview process, self-administered computerized (SAC) versions of the BDI/TDI have been developed to provide direct patient-reported ratings of dyspnea. To further establish the MCID of the interview-administered and/or the SAC TDI, we recommend that a patient's report of global ratings of change by used as an independent standard or anchor.     

Minimal clinically important difference in plain films in RA: group discussions, conclusions, and recommendations. OMERACT Imaging Task Force

Analysis of progression of structural damage on an individual patient level in randomized controlled trials provides extra information in addition to the analysis on a group level. A cutoff level is required to define which patients show progression and which patients do not. The objective of the mimimal clinically important difference (MCID) module for plain films was to elaborate the various concepts to determine a MCID for plain films, and if possible, to define a MCID for specific scoring methods. The module comprised preconference reading material, a plenary session, small group discussions, and a plenary report of the group sessions, combined with interactive voting. The following conclusions and recommendations were made: the smallest detectable difference (SDD) beyond measurement error is a good starting point to define MCID; SDD is study-specific; SDD should be reported for all radiographic endpoints used in a trial as a quality control; the expert panel approach is a reasonable method to define MCID, but defined in this way MCID may be smaller than current SDD; more research is needed to validate expert panel based MCID in different datasets and with different experts; a predictive, data driven MCID is the ultimate goal, but is not yet available; the SDD can be used as a proxy for MCID until a data driven MCID is available; analysis at the group level (comparison of means or medians) should remain primary in studies that include progression of joint damage as outcome measure; the proportion of patients showing more progression than the SDD is a secondary outcome measure.     

The MCID of the Transition Dyspnea Index is a Total Score of One Unit

The Baseline (BDI) and Transition (TDI) Dyspnea Indexes provide interview-based measurements of breathlessness related to activities of daily living. The BDI is a discriminative instrument that includes specific criteria for each of three components at a single point in time. The TDI is an evaluative instrument that includes specific criteria for each of three components to measure changes from a baseline state. Observational studies have shown that patients with COPD generally experience a gradual progression of breathing difficulty as measured by the TDI over time. Randomized controlled trials have demonstrated excellent measurement characteristics of the TDI; these include responsiveness (ability to detect change) and construct validity (a change in the TDI correlates with changes in other variables). Supporting evidence for one unit as the minimal clinically important difference (MCID) of the TDI is based on: expert preference; use of the physician's global evaluation score as an anchor; and distribution estimates (standard error of measurement and 0.5 of the standard deviation). As an alternative to the interview process, self-administered computerized (SAC) versions of the BDI/TDI have been developed to provide direct patient-reported ratings of dyspnea. To further establish the MCID of the interview-administered and/or the SAC TDI, we recommend that a patient's report of global ratings of change by used as an independent standard or anchor.     

Relevant change in radiological progression in patients with hip osteoarthritis. II. Determination using an expert opinion approach

AIM: To determine the minimum clinically important difference (MCID) in joint space width (JSW) progression in patients with hip osteoarthritis (OA), based upon evaluation by a panel of clinical experts as a gold standard. METHODS: A sample of 298 patients with hip OA was selected from a multicentre, prospective, longitudinal, 3-yr follow-up study. A pelvic radiograph was obtained at entry and after 3 yr. For each film, the narrowest JSW was measured using a 0.1-mm graduated magnifying glass. The difference between baseline and 3-yr follow-up JSW was calculated. Two senior rheumatologists, who were experts in osteoarthritis, evaluated each pair of films and noted whether a clinically relevant deterioration in osteoarthritis stage occurred at 3 yr compared with baseline. Interobserver reliabilities were evaluated using the kappa coefficient and proportions of agreements. Then, for each measured difference in JSW (0.1 mm per 0.1 mm), the sensitivity and specificity for MCID, defined as the assessment of expert 1, expert 2 or a combination of both, were calculated. This allowed us to obtain, from graphic representations of the correct classification probabilities, the best measured JSW threshold, with the maximal true positive and the minimal false positive results. RESULTS: The mean measured change in JSW was -0.63 +/- 0.74 mm. Experts 1 and 2 considered the decrease in JSW to be clinically relevant in 122 (40.9%) and 100 pairs (33.6%) respectively. The proportion of agreements between the experts was 79.9%, with a kappa coefficient of 0.572. The best measured JSW threshold was -0.4 mm for expert 1, expert 2 and the combination of both; sensitivity and specificity were 0.75 and 0.8, 0.71 and 0.72, and 0.75 and 0.7 respectively. CONCLUSION: This study suggests that a change of at least 0.4 mm in the radiological JSW could be considered clinically relevant. Other studies using other sets of patients and other methods are needed for validation.     

St. George's Respiratory Questionnaire: MCID

The SGRQ is a disease-specific measure of health status for use in COPD. A number of methods have been used for estimating its minimum clinically important difference (MCID). These include both expert and patient preference-based estimates. Anchor-based methods have also been used. The calculated MCID from those studies was consistently around 4 units, regardless of assessment method. By contrast, the MCID calculated using distribution-based methods varied across studies and permitted no consistent estimate. All measurements of clinical significance contain sample and measurement error. They also require value judgements, if not about the calculation of the MCID itself then about the anchors used to estimate it. Under these circumstances, greater weight should be placed upon the overall body of evidence for an MCID, rather than one single method. For that reason, estimates of MCID should be used as indicative values. Methods of analysing clinical trial results should reflect this, and use appropriate statistical tests for comparison with the MCID. Treatments for COPD that produced an improvement in SGRQ of the order of 4 units in clinical trials have subsequently found wide acceptance once in clinical practice, so it seems reasonable to expect any new treatment proposed for COPD to produce an advantage over placebo that is not significantly inferior to a 4-unit difference.     

St. George's Respiratory Questionnaire: MCID

The SGRQ is a disease-specific measure of health status for use in COPD. A number of methods have been used for estimating its minimum clinically important difference (MCID). These include both expert and patient preference-based estimates. Anchor-based methods have also been used. The calculated MCID from those studies was consistently around 4 units, regardless of assessment method. By contrast, the MCID calculated using distribution-based methods varied across studies and permitted no consistent estimate. All measurements of clinical significance contain sample and measurement error. They also require value judgements, if not about the calculation of the MCID itself then about the anchors used to estimate it. Under these circumstances, greater weight should be placed upon the overall body of evidence for an MCID, rather than one single method. For that reason, estimates of MCID should be used as indicative values. Methods of analysing clinical trial results should reflect this, and use appropriate statistical tests for comparison with the MCID. Treatments for COPD that produced an improvement in SGRQ of the order of 4 units in clinical trials have subsequently found wide acceptance once in clinical practice, so it seems reasonable to expect any new treatment proposed for COPD to produce an advantage over placebo that is not significantly inferior to a 4-unit difference.     

Minimal clinically important differences of the childhood health assessment questionnaire

OBJECTIVE: The Childhood Health Assessment Questionnaire (CHAQ) is a commonly used measure of disability and physical function for children with juvenile rheumatoid arthritis (JRA), whose scores range between 0 (no disability) and 3 (very severe disability), with a smallest potential difference in the CHAQ score of individuals at 0.125. We estimated minimal clinically important differences (MCID) of the CHAQ for worsening and improvement that were actually experienced by children with JRA using patient, parent, and clinical perspectives. METHODS: Changes in CHAQ scores were calculated for parent (n = 92) and patient ratings (children age > or = 8 yrs only; n = 67) between subsequent clinic visits. Changes in patient well being and disease activity and the occurrence of flare or important improvement between visits served as external standards for the MCID. MCID were defined as the median changes of the CHAQ scores of individual patients who had a minimal important improvement or worsening between visits. RESULTS: The median change in CHAQ scores of patients who rated themselves or were rated by others as unchanged was often 0. Depending on the external standard used, the MCID for improvement of the CHAQ was -0.188 at most, while the MCID for worsening was at most +0.125. CONCLUSION: The MCID of the CHAQ for both improvement and worsening are often at or close to the level of the smallest potential difference, suggesting that the CHAQ is relatively insensitive to important short term changes in children with JRA. This may warrant a change in the calculation of the global CHAQ score, or the development of more sensitive functional measures.     

Smallest detectable and minimal clinically important differences of rehabilitation intervention with their implications for required sample sizes using WOMAC and SF-36 quality of life measurement instruments in patients with osteoarthritis of the lower extremities

OBJECTIVE: To discuss the concepts of the minimal clinically important difference (MCID) and the smallest detectable difference (SDD) and to examine their relation to required sample sizes for future studies using concrete data of the condition-specific Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the generic Medical Outcomes Study 36-Item Short Form (SF-36) in patients with osteoarthritis of the lower extremities undergoing a comprehensive inpatient rehabilitation intervention. METHODS: SDD and MCID were determined in a prospective study of 122 patients before a comprehensive inpatient rehabilitation intervention and at the 3-month followup. MCID was assessed by the transition method. Required SDD and sample sizes were determined by applying normal approximation and taking into account the calculation of power. RESULTS: In the WOMAC sections the SDD and MCID ranged from 0.51 to 1.33 points (scale 0 to 10), and in the SF-36 sections the SDD and MCID ranged from 2.0 to 7.8 points (scale 0 to 100). Both questionnaires showed 2 moderately responsive sections that led to required sample sizes of 40 to 325 per treatment arm for a clinical study with unpaired data or total for paired followup data. CONCLUSION: In rehabilitation intervention, effects larger than 12% of baseline score (6% of maximal score) can be attained and detected as MCID by the transition method in both the WOMAC and the SF-36. Effects of this size lead to reasonable sample sizes for future studies lying below n = 300. The same holds true for moderately responsive questionnaire sections with effect sizes higher than 0.25. When designing studies, assumed effects below the MCID may be detectable but are clinically meaningless.     

Assessing the minimally clinically significant difference: scientific considerations, challenges and solutions

The scientific considerations surrounding the estimation of a minimally clinically important difference (MCID) are a myriad and challenging. There are a considerable number of hurdles to overcome. The good news is that there are solutions to virtually every one of the scientific hurdles. This paper intends to set out the issues, identify the challenges, and offer solutions so that the state of the science may move forward. The ultimate outcome of the paper may not be to provide a definitive answer for estimating the MCID in every situation, but it should provide a starting point and advice for a process or set of guidelines that may be followed toward achieving this goal. The paper begins with a brief synthesis of the literature and state of the science at the time of publication. The relationship between the process for determining MCIDs for other endpoints, such as tumor response or complete blood culture (CBC) variables, versus toxicity and QOL-related variables is described. The ultimate lessons to be learned from this exercise are: 1. There are many methods available to ascertaining an MCID. None are perfect, but all are useful. 2. All methods converge to similar answers. Supplementary information may refine answers from one or more of the methods. 3. Clinical opinion and patient subjective response should trump statistical theory. 4. A process of MCID estimation involving all approaches to produce a potential range with sensitivity analyses is the optimal solution to producing an MCID based on the most complete knowledge possible.     

Expanding the definition of clinical differences: from minimally clinically important differences to really important differences. Analyses in 8931 patients with rheumatoid arthritis

OBJECTIVE: Minimally clinically important differences (MCID) have become an important way to interpret data of randomized clinical trials (RCT), but do not reflect the degree of improvement consistent with a "really important difference" (RID). To define RID, we compared mean and/or least desirable clinical states with best and/or most desirable states. METHODS: In total, 8931 patients with rheumatoid arthritis (RA) < 65 years of age completed the Health Assessment Questionnaire (HAQ) and Medical Outcomes Survey Short Form 36 Physical Component Score (PCS). Definitions of RID were based on values for HAQ and PCS corresponding with the best and worst category of the following conditions: disabled vs not disabled: joint replacement vs no joint replacement; < poverty level vs > poverty level; very satisfied with health vs not; and independent in participation activities vs not. RESULTS: In contrast to published MCID values for the HAQ of approximately 0.22, RID was as high as 0.76 using objective reference conditions and 0.87 using the subjective measure of dependence vs independence. The HAQ score of independent RA patients was 0.38 (SD 0.45), and was 0.42 (SD 0.53) for those very satisfied with their health. The difference in HAQ scores between disabled and working patients was approximately 0.75. PCS differences were similarly increased. CONCLUSION: RID values are 3 to 4 times greater than MCID values. Although MCID are meaningful statistics for RCT, the RID percentage achieved [(actual improvement/RID) 100%] is a simple way to put the results of RCT in a broader perspective that gives an idea of how much additional treatment effect is needed.     

Minimal clinically important difference in radiological progression of joint damage. A definition based on patient perspective

OBJECTIVE: To estimate a threshold for minimal clinically important radiological progression of joint damage using its longitudinal relation with functional disability in patients with rheumatoid arthritis (RA). To validate existing estimates of minimal clinically important difference (MCID) using this relation with functional disability. METHODS: We reanalyzed published data of 185 patients with early RA followed for a maximum of 9 years. Longitudinal regression (mixed models) was used, relating radiological damage (modified Sharp score) to functional disability (HAQ-DI), correcting for age (age at diagnosis and increasing disease duration), disease activity (DAS28), and demographic variables. Several shapes of the relation were investigated. Based on the observed relationship between radiological damage, functional disability, and the minimal clinically relevant increase in functional disability found in earlier studies, MCID for progression of joint damage was discussed. Existing estimates of MCID were evaluated for their influence on functional disability over the disease course. RESULTS: A longitudinal relation between the modified Sharp score and the HAQ-DI was found. Significant covariates were age, gender, and disease activity. The model indicated that the relation between the Sharp score and the HAQ-DI was dependent on the amount of damage (a threshold effect) and on patients' age. With lower age, no effect of joint damage on functional disability could be demonstrated and with higher age the effect of joint damage increased. With a typical patient from our cohort (age at diagnosis 55 yrs, some baseline damage, and an expected disease duration of 30 yrs), a (constant) progression of 6 points per year led to an increase of about 0.2 on the HAQ score, solely related to damage, over the disease course. This estimate of MCID was close to estimates based on expert opinion and equal or smaller than most estimates based on the smallest detectable difference. CONCLUSIONS: The MCID, defined using longitudinal effect on functional disability, is dependent on age and (progression of) joint damage. However, with a typical patient population this MCID was similar to thresholds based on expert opinion, adding to the validity of these estimates.     

Smallest detectable and minimal clinically important differences of rehabilitation intervention with their implications for required sample sizes using WOMAC and SF‐36 quality of life measurement instruments in patients with osteoarthritis of the lower extremities

Objective

To discuss the concepts of the minimal clinically important difference (MCID) and the smallest detectable difference (SDD) and to examine their relation to required sample sizes for future studies using concrete data of the condition‐specific Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the generic Medical Outcomes Study 36‐Item Short Form (SF‐36) in patients with osteoarthritis of the lower extremities undergoing a comprehensive inpatient rehabilitation intervention.

Methods

SDD and MCID were determined in a prospective study of 122 patients before a comprehensive inpatient rehabilitation intervention and at the 3‐month followup. MCID was assessed by the transition method. Required SDD and sample sizes were determined by applying normal approximation and taking into account the calculation of power.

Results

In the WOMAC sections the SDD and MCID ranged from 0.51 to 1.33 points (scale 0 to 10), and in the SF‐36 sections the SDD and MCID ranged from 2.0 to 7.8 points (scale 0 to 100). Both questionnaires showed 2 moderately responsive sections that led to required sample sizes of 40 to 325 per treatment arm for a clinical study with unpaired data or total for paired followup data.

Conclusion

In rehabilitation intervention, effects larger than 12% of baseline score (6% of maximal score) can be attained and detected as MCID by the transition method in both the WOMAC and the SF‐36. Effects of this size lead to reasonable sample sizes for future studies lying below n = 300. The same holds true for moderately responsive questionnaire sections with effect sizes higher than 0.25. When designing studies, assumed effects below the MCID may be detectable but are clinically meaningless.

     

Minimal Clinically Important Differences in the Six-Minute Walk Test and the Incremental Shuttle Walking Test

Simple walking tests are widely used for the assessment of functional status in patients with cardiorespiratory disorders. These tests require far less instrumentation than formal cardiopulmonary exercise tests, but they do require standardization of procedures to achieve reproducible results. The most widely used tests for patients with COPD are the 6-minute walking test (6MWT) and the incremental shuttle walking test (SWT). The 6MWT has been characterized in COPD patients with respect to reproducibility and responsivity to change in health status. The 6MWT results are correlated with pulmonary function, health-related quality of life, maximum exercise capacity, and mortality. The minimal clinically important difference (MCID) for the 6MWT is conservatively estimated to be 54–80 meters using both distributional and discriminative methods. For an individual patient, the 6MWT would need to change by about 86 meters to be statistically confident that there has been a change. The SWT has been less extensively validated than the 6MWT, but has similar reproducibility in COPD (CV = approximately 20%). The SWT results improve with pulmonary rehabilitation and bronchodilation, and are highly correlated with maximum oxygen consumption. There are no studies that address the issue of MCID for the SWT. In addition to the MCID, the design and interpretation of COPD clinical trials should take into account the severity of initial impairment, the asymmetry between positive and negative changes, the proportion of patients who show substantial improvement, and the costs and risks of the treatment.     

Minimal clinically important differences in the six-minute walk test and the incremental shuttle walking test

Simple walking tests are widely used for the assessment of functional status in patients with cardiorespiratory disorders. These tests require far less instrumentation than formal cardiopulmonary exercise tests, but they do require standardization of procedures to achieve reproducible results. The most widely used tests for patients with COPD are the 6-minute walking test (6MWT) and the incremental shuttle walking test (SWT). The 6MWT has been characterized in COPD patients with respect to reproducibility and responsivity to change in health status. The 6MWT results are correlated with pulmonary function, health-related quality of life, maximum exercise capacity, and mortality. The minimal clinically important difference (MCID) for the 6MWT is conservatively estimated to be 54-80 meters using both distributional and discriminative methods. For an individual patient, the 6MWT would need to change by about 86 meters to be statistically confident that there has been a change. The SWT has been less extensively validated than the 6MWT, but has similar reproducibility in COPD (CV = approximately 20%). The SWT results improve with pulmonary rehabilitation and bronchodilation, and are highly correlated with maximum oxygen consumption. There are no studies that address the issue of MCID for the SWT. In addition to the MCID, the design and interpretation of COPD clinical trials should take into account the severity of initial impairment, the asymmetry between positive and negative changes, the proportion of patients who show substantial improvement, and the costs and risks of the treatment.     

Impact of hepatitis C on health related quality of life: a systematic review and quantitative assessment

Hepatitis C virus (HCV) diminishes health related quality of life (HRQOL), and it is now common to measure HRQOL in clinical trials. We sought to summarize the HRQOL data in HCV, and to establish the minimally clinically important difference (MCID) in HRQOL scores in HCV. We performed a systematic review to identify relevant studies, and converted HRQOL data from each study into clinically interpretable statistics. An expert panel used a modified Delphi technique to estimate the MCID in HCV. We found that patients with HCV scored lower than controls across all scales of the SF-36. Patients achieving sustained virological response (SVR) scored higher across all scales versus patients without SVR, especially in the physical health domains. HRQOL differences did not correspond with differences in liver histology or ALT levels. Based upon the published data, the expert panel concluded that the SF-36 vitality scale was most relevant in patients with HCV, and generated a mean MCID of 4.2 points on this scale. In conclusion, patients with HCV have a clinically significant decrement in HRQOL versus controls, and physical HRQOL improves in patients achieving SVR but not in those without SVR. The data further suggest that traditional outcomes fail to capture the full spectrum of illness related to chronic HCV. A difference of 4.2 points on the SF-36 vitality scale can be used as an estimate of the MCID in HCV, and this value may be used as the basis for power calculations in clinical trials evaluating HRQOL. Supplementary material for this article can be found on the HEPATOLOGY website (http://www.interscience.wiley.com/jpages/0270-9139/suppmat/index.html).     

Minimal clinically important differences in COPD lung function

The FEV1 is widely used by physicians in the diagnosis, staging, treatment, monitoring, and establishing prognosis for patients with COPD. The MCID is the smallest difference which patients perceive as beneficial and which would mandate a change in patient management. A precise MCID for FEV1 has not been established. In attempt to establish a MCID for predose or trough FEV1, several limitations need to be addressed. There are issues such as reproducibility, repeatability, acceptability, variability, placebo effect, and equipment effects. Patient factors, such as baseline level of FEV1, albuterol reversibility, diurnal variation, influence the results. Nonetheless, using anchoring techniques, a change in pre dose FEV1 of about 100 mL can be perceived by patients, correlates with fewer relapses following exacerbations and is in the range usually achieved with bronchodilators approved for COPD. In the future, consistent reporting of spirometric variables, such as a predose FEV1 and other outcomes, can be incorporated into a more quantitative effort to establish the MCID. Also distributional/statistical methods may be useful in determining the MCID FEV1.     

The Minimally Clinically Important Difference in Generic Utility-Based Measures

Purpose: To evaluate the use of utility-based generic quality of life measures for establishing the minimally clinically important difference (MCID). Background: Utility-based quality of life measures place levels of wellness on a continuum anchored by death (0.00) and optimum function (1.00). Preference measurement studies are used to define the meaning of points along the continuum. Health states that differ by less than 0.03 units cannot be discriminated by panels of judges as different from one another. Thus, 0.03 is a reasonable MCID for these measures. Method: Three published studies of patients with Chronic Obstructive Pulmonary Disease (COPD) reported data on the Quality of Well-being Scale (QWB) before and after pulmonary rehabilitation. One of the studies also randomly assigned patients to lung volume reduction surgery or to maximal medical therapy. These patients were followed for an average of 29 months. Results: All three evaluations of pulmonary rehabilitation showed changes on the QWB in excess of the proposed 0.03 MCID. QWB changes for patients assigned to lung volume reduction surgery were close to the MCID threshold at one year but grew stronger in subsequent years. Using Norman's 0.50 standard deviation method, all three estimates of rehabilitation effectiveness and the outcomes one year following surgery fall below the MCID. Conclusion: Different methods for estimating MCID lead to different conclusions about the meaning of quality of life changes following pulmonary rehabilitation and lung volume reduction surgery. The preference scaling system in generic utility-based quality of life measures provides a metric that is directly interpretable and avoids many of the criticisms of MCID measures. The method is sensitive enough to suggest clinically meaningful benefits of rehabilitation and surgery. Further, quality adjusted life years offer a valuable metric for policy analysis. Utility-based measures of health related quality of life should gain greater use in COPD outcomes research.