Surveying physicians to determine the minimal important difference: implications for sample-size calculation

The Meaning and Reliability of Minimal Important Differences (MIDs) for Clinician-Reported Outcome Measures (ClinROMs) in Dermatology-A Scoping Review

Background: Clinician-reported outcome measures (ClinROMs) are frequently used in clinical trials and daily practice to evaluate the disease status and evolution of skin disorders. The minimal important difference (MID) represents the smallest difference that decreases the disease impact enough to make a treatment change worthwhile for patients. As no clear guidance exists on the preferred method to calculate MIDs for ClinROMs, we evaluated how the published values for different skin disorders should be interpreted. Methods: A systematic search was performed for MIDs of ClinROMs that focus on skin disorders and/or symptoms. The results of the questions in the credibility instrument for MIDs of Devji et al., 2020 were analyzed to gain insights into the meaning of these MIDs. Results: 29 MIDs were identified. The most common skin diseases were atopic dermatitis/eczema, followed by bullous disorders and psoriasis. A minimal important difference from the patients’ perspective was determined in 31% of the cases. However, in 41.4% of the cases, it concerned a substantial rather than a minimal difference in disease severity rated by physicians. Over half (55.1%) of the studies contained an inadequate number of patients (n < 150). MID values increased substantially in patients with severe compared to mild disease. Conclusions: MIDs of ClinROMs for skin disorders should be carefully interpreted due to the substantial differences in methodology between the studies. There is an urgent need for a consensus method to report reliable MIDs. Otherwise, this lack of uniformity could not only affect the design and conclusion of clinical trials but also skew treatment decisions.

Improving mental health in U.S. Veterans using mHealth tools: A pilot study

Rates of PTSD remain elevated among U.S. Veterans, highlighting a need for innovative management tools. Previous studies have shown mobile apps to have positive effects on PTSD symptoms, but few apps have been examined systematically. This pilot study evaluated the perceived effectiveness and usability of Mindset, a novel mobile app that monitors user stress level via heart rate to encourage e-therapy use. The study sample included 30 community-residing Veterans who completed baseline assessments. They used the Mindset app and associated smartwatch until their approximate 1-month follow-up. Self-reported assessments included pre- and post-deployment experiences; experience with Mindset; and standard screeners for PTSD (PCL-M), anxiety (GAD-7), depression (PHQ-9), and alcohol use problems (AUDIT). Among the 24 participants who completed follow-up interviews, a significant decrease (p < 0.05) was found in PCL-M, PHQ-9, and modified AUDIT scores. Respondents reported moderate to high acceptance and satisfaction with Mindset features, though considerable frustration with the associated smartwatch. These findings highlight mHealth apps such as Mindset as potentially useful tools for PTSD and depression symptom management. These findings are also encouraging in the context of the current COVID-19 pandemic, which may accelerate further innovation and implementation of mHealth technologies to improve mental health self-care.

Clinical trials in critical care: can a Bayesian approach enhance clinical and scientific decision making?

Recent Bayesian reanalyses of prominent trials in critical illness have generated controversy by contradicting the initial conclusions based on conventional frequentist analyses. Many clinicians might be sceptical that Bayesian analysis, a philosophical and statistical approach that combines prior beliefs with data to generate probabilities, provides more useful information about clinical trials than the frequentist approach. In this Personal View, we introduce clinicians to the rationale, process, and interpretation of Bayesian analysis through a systematic review and reanalysis of interventional trials in critical illness. In the majority of cases, Bayesian and frequentist analyses agreed. In the remainder, Bayesian analysis identified interventions where benefit was probable despite the absence of statistical significance, where interpretation depended substantially on choice of prior distribution, and where benefit was improbable despite statistical significance. Bayesian analysis in critical care medicine can help to distinguish harm from uncertainty and establish the probability of clinically important benefit for clinicians, policy makers, and patients.

Reliability and Responsiveness of the Observable Movement Quality Scale for Children with Mild to Moderate Motor Impairments

AIM

The Observable Movement Quality (OMQ) scale measures generic movement quality and is used alongside standardized age-adequate motor performance tests. The scale consists of 15 items, each focusing on a different aspect; together, the entire construct of movement quality is assessed. This study aimed to determine interrater and intrarater reliability, and responsiveness of the OMQ scale.

METHODS

A prospective intervention study with pre-post design in pediatric physical therapy practices. For interrater reliability, 3 physical therapists observed video-recorded motor assessments of 30 children with mild to moderate motor impairments -aged 4 to 12 years-using the OMQ scale. One therapist scored baseline assessment a second time for intrarater reliability, and to calculate smallest detectable change (SDC). Responsiveness (n = 28) was tested by comparing outcomes before and after intervention.

RESULTS

Interrater reliability was moderate to good (ICC_2,1: 0.79); intrarater reliability was high (ICC_2,1: 0.97). Responsiveness results revealed an SDC of 2.4 and a minimal important change of 2.5; indicating sufficient validity in differentiating groups of children showing improved versus unchanged movement quality.

CONCLUSION

The OMQ scale is reliable and responsive to change when used to assess movement quality in clinical practice for children with mild to moderate motor impairments, aged 4-12 year.

What change in outcomes after cardiac arrest is necessary to change practice? Results of an international survey

BACKGROUND

Efficient trials of interventions for patients with out-of-hospital cardiac arrest (OHCA) should have adequate but not excess power to detect a difference in outcomes. The minimum clinically important difference (MCID) is the threshold value in outcomes observed in a trial at which providers should choose to adopt a treatment. There has been limited assessment of MCID for outcomes after OHCA. Therefore, we conducted an international survey of individuals interested in cardiac resuscitation to define the MCID for a range of outcomes after OHCA.

METHODS

A brief survey instrument was developed and modified by consensus. Included were open-ended responses. The survey included an illustrative example of a hypothetical randomized study with distributions of outcomes based on those in a public use datafile from a previous trial. Elicited information included the minimum significant difference required in an outcome to change clinical practice. The population of interest was emergency physicians or other practitioners of acute cardiovascular research.

RESULTS

Usable responses were obtained from 160 respondents (50% of surveyed) in 46 countries (79% of surveyed). MCIDs tended to increase as baseline outcomes increased. For a population of patients with 25% survival to discharge and 20% favorable neurologic status at discharge, the MCID were median 5 (interquartile range [IQR] 3, 10) percent for survival to discharge; median 5 (IQR 2, 10) percent for favorable neurologic status at discharge, median 4 (IQR 2, 9) days of ICU-free survival and median 4 (IQR 2, 8) days of hospital-free survival.

CONCLUSION

Reported MCIDs for outcomes after OHCA vary according to the outcome considered as well as the baseline rate of achieving it. MCIDs of ICU-free survival or hospital-free survival may be useful to accelerate the rate of evidence-based change in resuscitation care.

How do researchers determine the difference to be detected in superiority trials? Results of a survey from a panel of researchers

BACKGROUND

There is currently no guidance for selecting a specific difference to be detected in a superiority trial. We explored 3 factors that in our opinion should influence the difference to be detected (type of outcome, patient age group, and presence of treatment side-effects), and 3 that should not (baseline level of risk, logistical difficulties, and cost of treatment).

METHODS

We conducted an experimental survey using a factorial design among 380 corresponding authors of randomized controlled trials indexed in Medline. Two hypothetical vignettes were submitted to participants: one described a trial of a new analgesic in mild trauma injuries, the other described a trial of a new chemotherapy among cancer patients. The first vignette tested the baseline level of risk, patient age-group, patient recruitment difficulties, and treatment side-effects. The second tested the baseline level of risk, patient age-group, type of outcome, and cost of treatment. The respondents were asked to select the smallest gain of effectiveness that should be detected by the trial.

RESULTS

In vignette 1, respondents selected a median difference to be detected corresponding to an improvement of 7.0 % in pain control with the new treatment. In vignette 2, they selected a median difference to be detected corresponding to a reduction of 5.0 % in mortality or cancer recurrence with the new chemotherapy. In both vignettes, the difference to be detected decreased significantly with the baseline risk. The other factor influencing difference to be detected was the age group, but the impact of this factor was smaller. Cost, side-effects, outcome severity, or mention of logistical difficulties did not significantly impact the difference to be detected selected by participants.

CONCLUSIONS

Three of the anticipated effects conformed to our expectations (the effect of patient age, and absence of effect of the cost of treatment and of patient recruitment difficulties) and the other three did not. These findings can guide future research in determining differences to be detected in trials that can translate to meaningful clinical decision-making.

Multicentre study of abdominal aortic aneurysm measurement and enlargement

Background

No effective treatment is currently available to prevent progression of small and medium-sized abdominal aortic aneurysms (AAAs). Identification of drugs with sufficient promise to justify large expensive randomized trials remains challenging. One potentially useful strategy is to look for associations between commonly used drugs and AAA enlargement in appropriately adjusted observational studies.

Methods

Potential AAA measurements were identified from abdominal imaging reports in the electronic data files of three medical centres from 1995 to 2010. AAA measurements were extracted manually and patients with an aneurysm of 3 cm or larger, who had at least two measurements over an interval of at least 6 months, were identified. Other data were obtained from the electronic data files (demographics, co-morbidities, smoking status, drug use) to conduct a propensity analysis of the associations of drugs and other factors with AAA enlargement.

Results

From 52 962 abdominal imaging studies, 5362 patients with an AAA of 3 cm or more were identified, of whom 2428 had at least two measurements over at least 6 months. Mean AAA follow-up was 3·4 years and the mean AAA enlargement rate was 2·0 mm per year. Propensity analysis demonstrated no significant association of AAA enlargement with statins, beta-blockers, angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. Diabetes was associated with a reduction in AAA enlargement of 1·2 mm per year (P = 0·008), and chronic obstructive pulmonary disease was associated with increased enlargement (0·5 mm per year; P = 0·050). Moderate AAA measurement variation and substantial terminal digit preference were also observed, but the digit preference became less pronounced after 2000.

Conclusion

This study confirms the negative association of diabetes with AAA progression. There was no evidence that commonly used cardiovascular drugs affect AAA enlargement.

Estimating minimally important difference (MID) in PROMIS pediatric measures using the scale-judgment method

OBJECTIVE

To assess minimally important differences (MIDs) for several pediatric self-report item banks from the National Institutes of Health Patient-Reported Outcomes Measurement Information System(®) (PROMIS(®)).

METHODS

We presented vignettes comprising sets of two completed PROMIS questionnaires and asked judges to declare whether the individual completing those questionnaires had an important change or not. We enrolled judges (including adolescents, parents, and clinicians) who responded to 24 vignettes (six for each domain of depression, pain interference, fatigue, and mobility). We used item response theory to model responses to the vignettes across different judges and estimated MID as the point at which 50 % of the judges would declare an important change.

RESULTS

We enrolled 246 judges (78 adolescents, 85 parents, and 83 clinicians). The MID estimated with clinician data was about 2 points on the PROMIS T-score scale, and the MID estimated with adolescent and parent data was about 3 points on that same scale.

CONCLUSIONS

The MIDs enhance the value of PROMIS pediatric measures in clinical research studies to identify meaningful changes in health status over time.

A survey of physicians show a one-third reduction in harmful outcomes to be a clinically important difference for statin therapy

OBJECTIVE

To establish a minimal clinically important difference (MCID) for outcomes of statin therapy with physicians using a cross-sectional design. The MCID was defined as the smallest benefit of statin therapy that would result in physicians recommending it to their patients after considering potential harm and cost.

STUDY DESIGN AND SETTING

A self-administered questionnaire was sent to family practitioners, internal medicine specialists, and cardiologists practicing in Hamilton. They provided an MCID of statin therapy using clinical scenarios based on 5-year risk of vascular outcomes, namely coronary death, nonfatal myocardial infarction, stroke, and coronary revascularization.

RESULTS

Two hundred nine physicians participated, of which 638 were initially approached. Physicians would recommend statin therapy if it would at least reduce the relative risk of vascular events by about one-third. For patient scenarios involving a 30%, 13%, and 5% baseline risk of developing a vascular event in 5 years, physicians would recommend treatment if it would reduce the baseline risk by 31.4% (standard deviation [SD], 19.8), 34.6% (SD, 18.0), and 46.2% (SD, 24.6), respectively.

CONCLUSION

Physicians were consistent in their choice of MCID for statin therapy across vascular events. They required a larger benefit of statin therapy for patients at a lower baseline risk (5%) of developing a vascular event before they would recommend treatment.

SF-6D utility index as measure of minimally important difference in health status change

OBJECTIVES

To combine anchor- and distribution-based approaches to identify minimally important differences (MIDs) for the short-form six-dimension utility index (SF-6D) and to identify variables associated with self-reported health status change.

DESIGN

Descriptive, exploratory, nonexperimental study.

SETTING

United States between April 1, 1999, and October 31, 1999.

PATIENTS

2,317 participants of SADD-Sx (Study of Antihypertensive Drugs and Depressive Symptoms), aged 50 years or older and with hypertension and coronary artery disease.

INTERVENTION

Patients were randomized into a verapamil SR- or atenolol-led hypertensive treatment strategy and mailed baseline and 1-year surveys.

MAIN OUTCOME MEASURE

SF-6D utility scores for patients completing both surveys.

RESULTS

The pooled mean (±SD) MID change on the SF-6D of patients whose health status minimally changed was 0.035 ± 0.095. The anchor-based change scores had a median value of 0.036 (interquartile range -0.03 to 0.10). One-third and one-half of the SD of SF-6D change scores were 0.035 and 0.053, respectively. Whites were less likely to report minimally improved health status compared with nonwhites (odds ratio 0.59 [95% CI 0.40-0.88]). Change in SF-6D scores improved prediction of health status change.

CONCLUSION

We recommend using the MID range based on all patients combined (-0.03 to 0.10) to interpret SF-6D scores. These estimates can be used in conjunction with other measures of efficacy to determine meaningful changes. SF-6D demonstrates potential utility in predicting minimally important improvement or worsening among patients receiving different pharmacologic medications.

Is it possible to estimate the minimal clinically important treatment effect needed to change practice in preterm birth prevention? Results of an obstetrician survey used to support the design of a trial

Background

Sample sizes for obstetrical trials are often based on the opinion of investigators about clinically important effect size. We surveyed Canadian obstetricians to investigate clinically important effect sizes required before introducing new treatments into practice to prevent preterm birth.

Methods

Questionnaires were mailed to practicing obstetricians, asking the magnitude of pregnancy prolongation required to introduce treatments into practice. The three prophylactic treatments were of increasing invasiveness: vaginal progesterone, intramuscular progesterone, and cervical cerclage. We also asked about the perceived most relevant outcome measures for obstetrical trials and current obstetrical practice in preterm birth prevention.

Results

544/1293(42.1%) completed questionnaires were received. The majority of respondents required one or two weeks' increase in length of gestation before introducing vaginal (372,77.1%), and intramuscular progesterone(354,67.9%). At least three weeks increase was required before introducing prophylactic cervical cerclage(326,62.8%). Clinicians who already used a treatment required a smaller difference before introducing it into practice. Decreasing neonatal morbidity was cited as the most important outcome for obstetrical trials (349,72.2%).

Conclusion

Obstetricians would require a larger increase in treatment effect before introducing more invasive treatments into practice. Although infant morbidity was perceived as a more important outcome, clinicians appeared willing to change practice on the basis of prolongation of pregnancy, a surrogate outcome. We found that there is not a single minimum clinically important treatment effect that will influence all practising clinicians: rather the effect size that will influence physicians is affected by the nature of the treatment, the reported outcome measure and the clinician's own current clinical practice.

Comparison of distribution- and anchor-based approaches to infer changes in health-related quality of life of prostate cancer survivors

OBJECTIVE

To determine the minimal important difference (MID) in generic and prostate-specific health-related quality of life (HRQoL) using distribution- and anchor-based methods.

STUDY DESIGN AND SETTING

Prospective cohort study of 602 newly diagnosed prostate cancer patients recruited from an urban academic hospital and a Veterans Administration hospital. Participants completed generic (SF-36) and prostate-specific HRQoL surveys at baseline and at 3, 6, 12, and 24 months posttreatment. Anchor-based and distribution-based methods were used to develop MID estimates. We compared the proportion of participants returning to baseline based on MID estimates from the two methods.

RESULTS

MID estimates derived from combining distribution- and anchor-based methods for the SF-36 subscales are physical function = 7, role physical = 14, role emotional = 12, vitality = 9, mental health = 6, social function = 9, bodily pain = 9, and general health = 8; and for the prostate-specific scales are urinary function = 8, bowel function = 7, sexual function = 8, urinary bother = 9, bowel bother = 8, and sexual bother = 11. Proportions of participants returning to baseline values corresponding to MID estimates from the two methods were comparable.

CONCLUSIONS

This is the first study to assess the MID for generic and prostate-specific HRQoL using anchor-based and distribution-based methods. Although variation exists in the MID estimates derived from these two methods, the recovery patterns corresponding to these estimates were comparable.

Using alternative statistical formats for presenting risks and risk reductions

BACKGROUND

The success of evidence-based practice depends on the clear and effective communication of statistical information.

OBJECTIVES

To evaluate the effects of using alternative statistical presentations of the same risks and risk reductions on understanding, perception, persuasiveness and behaviour of health professionals, policy makers, and consumers.

SEARCH STRATEGY

We searched Ovid MEDLINE (1966 to October 2007), EMBASE (1980 to October 2007), PsycLIT (1887 to October 2007), and the Cochrane Central Register of Controlled Trials (The Cochrane Library, 2007, Issue 3). We reviewed the reference lists of relevant articles, and contacted experts in the field.

SELECTION CRITERIA

We included randomized and non-randomized controlled parallel and cross-over studies. We focused on four comparisons: a comparison of statistical presentations of a risk (eg frequencies versus probabilities) and three comparisons of statistical presentation of risk reduction: relative risk reduction (RRR) versus absolute risk reduction (ARR), RRR versus number needed to treat (NNT), and ARR versus NNT.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies for inclusion, extracted data, and assessed risk of bias. We contacted investigators to obtain missing information. We graded the quality of evidence for each outcome using the GRADE approach. We standardized the outcome effects using adjusted standardized mean difference (SMD).

MAIN RESULTS

We included 35 studies reporting 83 comparisons. None of the studies involved policy makers. Participants (health professionals and consumers) understood natural frequencies better than probabilities (SMD 0.69 (95% confidence interval (CI) 0.45 to 0.93)). Compared with ARR, RRR had little or no difference in understanding (SMD 0.02 (95% CI -0.39 to 0.43)) but was perceived to be larger (SMD 0.41 (95% CI 0.03 to 0.79)) and more persuasive (SMD 0.66 (95% CI 0.51 to 0.81)). Compared with NNT, RRR was better understood (SMD 0.73 (95% CI 0.43 to 1.04)), was perceived to be larger (SMD 1.15 (95% CI 0.80 to 1.50)) and was more persuasive (SMD 0.65 (95% CI 0.51 to 0.80)). Compared with NNT, ARR was better understood (SMD 0.42 (95% CI 0.12 to 0.71)), was perceived to be larger (SMD 0.79 (95% CI 0.43 to 1.15)).There was little or no difference for persuasiveness (SMD 0.05 (95% CI -0.04 to 0.15)). The sensitivity analyses including only high quality comparisons showed consistent results for persuasiveness for all three comparisons. Overall there were no differences between health professionals and consumers. The overall quality of evidence was rated down to moderate because of the use of surrogate outcomes and/or heterogeneity. None of the comparisons assessed behaviourbehaviour.

AUTHORS' CONCLUSIONS

Natural frequencies are probably better understood than probabilities. Relative risk reduction (RRR), compared with absolute risk reduction (ARR) and number needed to treat (NNT), may be perceived to be larger and is more likely to be persuasive. However, it is uncertain whether presenting RRR is likely to help people make decisions most consistent with their own values and, in fact, it could lead to misinterpretation. More research is needed to further explore this question.

What differences are detected by superiority trials or ruled out by noninferiority trials? A cross-sectional study on a random sample of two-hundred two-arms parallel group randomized clinical trials

BACKGROUND

The smallest difference to be detected in superiority trials or the largest difference to be ruled out in noninferiority trials is a key determinant of sample size, but little guidance exists to help researchers in their choice. The objectives were to examine the distribution of differences that researchers aim to detect in clinical trials and to verify that those differences are smaller in noninferiority compared to superiority trials.

METHODS

Cross-sectional study based on a random sample of two hundred two-arm, parallel group superiority (100) and noninferiority (100) randomized clinical trials published between 2004 and 2009 in 27 leading medical journals. The main outcome measure was the smallest difference in favor of the new treatment to be detected (superiority trials) or largest unfavorable difference to be ruled out (noninferiority trials) used for sample size computation, expressed as standardized difference in proportions, or standardized difference in means. Student t test and analysis of variance were used.

RESULTS

The differences to be detected or ruled out varied considerably from one study to the next; e.g., for superiority trials, the standardized difference in means ranged from 0.007 to 0.87, and the standardized difference in proportions from 0.04 to 1.56. On average, superiority trials were designed to detect larger differences than noninferiority trials (standardized difference in proportions: mean 0.37 versus 0.27, P = 0.001; standardized difference in means: 0.56 versus 0.40, P = 0.006). Standardized differences were lower for mortality than for other outcomes, and lower in cardiovascular trials than in other research areas.

CONCLUSIONS

Superiority trials are designed to detect larger differences than noninferiority trials are designed to rule out. The variability between studies is considerable and is partly explained by the type of outcome and the medical context. A more explicit and rational approach to choosing the difference to be detected or to be ruled out in clinical trials may be desirable.

Better health-related quality of life after switching from a virologically effective regimen to a regimen containing efavirenz or nevirapine

Switching antiretroviral therapy has been shown as safe and effective, but its impact on health-related quality of life (HRQL) was rarely measured. Our objective was to assess changes in HRQL after switching to an non-nucleoside reverse transcriptase inhibitors (NNRTI) containing regimen among NNRTI-naive HIV-infected patients with viral load (VL) <500 copies/mL. In this prospective observational study, the Hospital Anxiety and Depression, Symptoms checklist, specific World Health Organization Quality of Life (WHOQoL) and generic SF-12v2 HRQL questionnaires were used to assess anxiety, depression, symptoms, and HRQL at baseline and months 1 (M1), 6 (M6), and 12 (M12). The statistical significance of changes in the frequency of anxiety and depression was determined with the McNemar test. Mean changes in the number of symptoms and in HRQL scores were compared using Wilcoxon's paired test. Data were available for 239 patients at baseline (162 with a switch to nevirapine) and for 164 patients at M6. The median age of the patients was 42 years and 67% of patients were male. The proportion of anxious patients diminished at M6 (11%, P=0.02) but not yet at M1. There was no change in the frequency of depression. Significant reductions (p<0.01) were observed at M6 in the mean number of all symptoms (-3.3), lipodystrophy symptoms (-0.8), other symptoms (-2.5), bothersome symptoms (-1.7), bothersome lipodystrophy symptoms (-0.4), and bothersome other symptoms (-1.3). HRQL as assessed with WHOQoL, improved in the physical, independence, and spirituality domains, with a small effect sizes at M6. Both for symptoms and HRQL, these changes were already significant at M1 and persisted at M12. This study shows that in patients with controlled VL, switching to an NNRTI regimen was associated with less anxiety, fewer perceived symptoms, and a small improvement in HRQL, while maintaining virological suppression.

[Recommendations for the clinical evaluation of results in the biomedical literature]

The assessment and interpretation of the results of a clinical study are a real challenge for the clinicians. In this paper we establish a general basis for a critical and reserved assessment of these, from the fundamental aspects of the design and statistics, as well as the application of the results to our own patients according to risk and benefit criteria. Main errors and the traps that should be avoided are emphasised.

People with low back pain typically need to feel 'much better' to consider intervention worthwhile: an observational study

QUESTIONS

How much of an effect do five common physiotherapy interventions need to have for patients with low back pain to perceive they are worth their cost, discomfort, risk, and incovenience? Are there any differences between the interventions? Do specific characteristics of people with low back pain predict the smallest important difference?

DESIGN

Cross-sectional, observational study.

PARTICIPANTS

77 patients with non-specific low back pain who had not yet commenced physiotherapy intervention.

OUTCOME MEASURES

The smallest worthwhile effect was measured in terms of global perceived change (0 to 4) and percentage perceived change.

RESULTS

Participants perceived that intervention would have to make them 'much better', which corresponded to 1.7 (SD 0.7) on the 4-point scale, or improve their symptoms by 42% (SD 23), to make it worthwhile. There was little distinction made between interventions, regardless of whether smallest worthwhile effects were quantified as global perceived change (p = 0.09) or percentage perceived change (p = 1.00). Severity of symptoms independently (p = 0.01) predicted percentage perceived change explaining 9% of the variance, so that for each increase in severity of symptoms of 1 point out of 10 there was an increase of 4% in the percentage perceived change that participants considered would make intervention worthwhile.

CONCLUSIONS

Typically people with low back pain feel that physiotherapy intervention must reduce their symptoms by 42%, or make them feel 'much better' for intervention to be worthwhile.

Systematic review of hydroxychloroquine use in pregnant patients with autoimmune diseases

OBJECTIVE

The purpose of this study is to compare the incidence of congenital defects, spontaneous abortions, number of live births, fetal death and pre-maturity in women with autoimmune diseases taking HCQ during pregnancy.

METHODS

The authors searched MEDLINE, Cochrane data base, Ovid-Currents Clinical Medicine, Ovid-Embase:Drugs and Pharmacology, EBSCO, Web of Science, and SCOPUS using the search terms HCQ and/or pregnancy. We attempted to identify all clinical trials from 1980 to 2007 regardless of language or publication status. We also searched Cochrane Central Library and http://www.Clinical trials.gov for clinical trials of HCQ and pregnancy. Data were extracted onto standardized forms and were confirmed.

RESULTS

The odds ratio (OR) of congenital defects in live births of women taking HCQ during pregnancy was 0.66, 95% confidence intervals (CI) 0.25, 1.75. The OR of a live birth for women taking HCQ during pregnancy was 1.05 (95% CI 0.58, 1.93). The OR of spontaneous abortion in women taking HCQ during pregnancy was 0.92 (95% CI 0.49, 1.72). The OR of fetal deaths in women taking HCQ during pregnancy was 0.97 (95% CI 0.14, 6.54). The OR of pre-mature birth defined as birth before 37 weeks in women taking HCQ during pregnancy was 1.10 (95% CI 0.75, 1.61).

CONCLUSION

HCQ is not associated with any increased risk of congenital defects, spontaneous abortions, fetal death, pre-maturity and decreased numbers of live births in patients with auto-immune diseases.

Nocturnal oxygen therapy in patients with chronic obstructive pulmonary disease: a survey of Canadian respirologists

BACKGROUND

Current evidence does not clearly support the provision of nocturnal oxygen therapy in patients with chronic obstructive pulmonary disease (COPD) who desaturate during sleep but who would not otherwise qualify for long-term oxygen therapy (LTOT).

OBJECTIVES

To characterize the perception and clinical practice of Canadian respirologists regarding the indications and prescription of nocturnal oxygen therapy in COPD, and to determine what Canadian respirologists consider an important treatment effect of nocturnal oxygen therapy in a randomized, placebo-controlled trial.

METHODS

A mail survey of all the respirologists registered in the 2006 Canadian Medical Directory was conducted.

RESULTS

A total of 543 physicians were surveyed. The response rate was 60%, and 99% of the respondents indicated that the problem of nocturnal oxygen desaturation is clinically relevant. Eighty-two per cent interpret oximetry tracings themselves, and 87% have access to a sleep laboratory. Forty-two per cent believe that all COPD patients with significant nocturnal desaturation should have a polysomnography to rule out sleep apnea, and 41% would prescribe nocturnal oxygen therapy to active smokers. Assuming a risk of death or progression to LTOT of 40% over a three-year period, the respirologists indicated that to declare nocturnal oxygen therapy effective in reducing the rate of major clinical events in a clinical trial, the minimal absolute risk difference of death or progression to LTOT between oxygen and room air breathing should be 14%.

CONCLUSIONS

Canadian respirologists are interested in the issue of nocturnal oxygen desaturation in COPD. There is variation in clinical practices among Canadian respirologists in several aspects of the management of this problem.

Comparison of anchor-based and distributional approaches in estimating important difference in common cold

CONTEXT

Evaluative health-related quality-of-life instruments used in clinical trials should be able to detect small but important changes in health status. Several approaches to minimal important difference (MID) and responsiveness have been developed.

OBJECTIVES

To compare anchor-based and distributional approaches to important difference and responsiveness for the Wisconsin Upper Respiratory Symptom Survey (WURSS), an illness-specific quality of life outcomes instrument.

DESIGN

Participants with community-acquired colds self-reported daily using the WURSS-44. Distribution-based methods calculated standardized effect size (ES) and standard error of measurement (SEM). Anchor-based methods compared daily interval changes to global ratings of change, using: (1) standard MID methods based on correspondence to ratings of "a little better" or "somewhat better," and (2) two-level multivariate regression models.

PARTICIPANTS

About 150 adults were monitored throughout their colds (1,681 sick days.): 88% were white, 69% were women, and 50% had completed college. The mean age was 35.5 years (SD = 14.7).

RESULTS

WURSS scores increased 2.2 points from the first to second day, and then dropped by an average of 8.2 points per day from days 2 to 7. The SEM averaged 9.1 during these 7 days. Standard methods yielded a between day MID of 22 points. Regression models of MID projected 11.3-point daily changes. Dividing these estimates of small-but-important-difference by pooled SDs yielded coefficients of .425 for standard MID, .218 for regression model, .177 for SEM, and .157 for ES. These imply per-group sample sizes of 870 using ES, 616 for SEM, 302 for regression model, and 89 for standard MID, assuming alpha = .05, beta = .20 (80% power), and two-tailed testing.

CONCLUSIONS

Distribution and anchor-based approaches provide somewhat different estimates of small but important difference, which in turn can have substantial impact on trial design.

Improving drug trials for mild to moderate Alzheimer's disease

Over the last two decades, numerous studies have been conducted on subjects with mild to moderate Alzheimer's disease. The objective of this paper was to review concerns raised in the literature about the design and methodology of these clinical trials and to make recommendations to deal with the limitations identified. Concerns raised in the literature include the following: undue focus on statistical rather than clinical significance; the need for further pharmacoeconomic evaluations; the nonrepresentativeness of the study populations; perceived inadequacies in the direct-comparison studies conducted to date; the limitations of open-label extension studies; the inability of standard psychometric tools to document all the relevant treatment effects; the ethics of placebo-controlled trials; and, problems caused by the actions of the regulatory authorities. Recommendations are made to deal with the issues raised.

Reliability, validity, and minimally important differences of the SF-6D in systemic sclerosis

OBJECTIVES

To evaluate the reliability and validity and estimate the minimally important difference (MID) for the SF-6D in patients with systemic sclerosis (SSc). Subjects We used data from two clinical studies to analyze the SF-6D in patients with SSc: Study 1 was a cross-sectional observational study (N = 107) designed to assess three direct preference measures--the rating scale, time trade-off, and standard gamble (SG) in patients with diffuse SSc and limited SSc, and Study 2 was a 12-month randomized, placebo-controlled, clinical trial (N = 168) assessing oral bovine collagen versus placebo in diffuse SSc.

METHODS

We assessed the test-retest reliability of the SF-6D in Study 2 over a mean (SD) 4.8 (3.0)-week interval and the agreement between the SF-6D and direct preference measures in Study 1 using intraclass correlations (ICC). The MID was estimated using three different anchors--the SF-36 change in health item (patients who answered "somewhat better" formed the MID group), the Health Assessment Questionnaire-Disability Index (HAQ-DI; change of > or =0.14 and > or =0.22) and the skin score (change of > or =5.3). Results The mean (SD) SF-6D scores were 0.61 (0.12) in Study 1 and 0.64 (0.13) in Study 2. Test-retest reliability for the SF-6D was high (ICC = 0.82 [95% CI: 0.76, 0.87]). Agreement between the SF-6D and three direct preferences measures was poor to moderate (0.16-0.52). The MID estimate for the SF-6D using the change in SF-36 item -0.012 and this level of change was similar to the no change group. The mean MID estimate for the SF-6D improvement using the HAQ-DI and skin score as anchors was 0.035 (effect size of 0.27).

CONCLUSION

This is the first study to assess the SF-6D in SSc. The SF-6D is reliable and valid in patients with SSc. We provide MID estimates that can aid in calculating sample size for clinical trials involving patients with diffuse SSc.

Minimally important change determined by a visual method integrating an anchor-based and a distribution-based approach

BACKGROUND

Minimally important changes (MIC) in scores help interpret results from health status instruments. Various distribution-based and anchor-based approaches have been proposed to assess MIC.

OBJECTIVES

To describe and apply a visual method, called the anchor-based MIC distribution method, which integrates both approaches.

METHOD

Using an anchor, patients are categorized as persons with an important improvement, an important deterioration, or without important change. For these three groups the distribution of the change scores on the health status instrument are depicted in a graph. We present two cut-off points for an MIC: the ROC cut-off point and the 95% limit cut-off point.

RESULTS

We illustrate our anchor-based MIC distribution method determining the MIC for the Pain Intensity Numerical Rating Scale in patients with low back pain, using two conceivable definitions of minimal important change on the anchor. The graph shows the distribution of the scores of the health status instrument for the relevant categories on the anchor, and also the consequences of choosing the ROC cut-off point or the 95% limit cut-off point.

DISCUSSION

The anchor-based MIC distribution method provides a general framework, applicable to all kind of anchors. This method forces researchers to choose and justify their choice of an appropriate anchor and to define minimal importance on that anchor. The MIC is not an invariable characteristic of a measurement instrument, but may depend, among other things, on the perspective from which minimal importance is considered and the baseline values on the measurement instrument under study. A balance needs to be struck between the practicality of a single MIC value and the validity of a range of MIC values.

Determination of clinically meaningful levels of pain reduction in patients experiencing acute postoperative pain

Assessment is an essential, but challenging, component of any pain management plan. Nurses who care for postoperative patients quantify and document pain by use of unidimensional scales such as the numeric rating scale, the visual analogue scale, or a verbal descriptor scale. Improvements in pain ratings on these scales are viewed as a welcome result by nurses and doctors. Pain, however, is a multidimensional phenomenon. Furthermore, pain is subjective, and therefore no objective measure of pain exists that captures every aspect of the pain experience. Given that clinical decisions are made on the basis of existing scales, it is important to know how much reduction in pain is clinically meaningful from the patient's perspective. The aim of this study was to investigate this issue by comparing levels of postsurgical pain reduction measured by a numeric rating scale (NRS) with the patients' verbal descriptions of how meaningful they consider their pain reduction to be. A convenience sample of 150 postoperative patients was obtained. The patients' postoperative pain intensity levels before and after analgesia were measured and compared with their verbal descriptions of what constitutes a clinically meaningful pain reduction. The results of the study showed a significant correlation between the percentage of reduction in pain severity and the patients' descriptive ratings of pain improvement. A unique finding of the study was that the degree of incremental shift on an NRS of pretreatment and posttreatment pain levels is not a good predictor of clinical relevance from the patient's perspective. A more accurate predictor was found by converting the changes on the NRS to percentages. An important implication of this study is the need to include a scale in pain assessment instruments for assessing the level of clinical meaningfulness of pain reduction from the patient's perspective.

Minimally important change determined by a visual method integrating an anchor-based and a distribution-based approach

BACKGROUND

Minimally important changes (MIC) in scores help interpret results from health status instruments. Various distribution-based and anchor-based approaches have been proposed to assess MIC.

OBJECTIVES

To describe and apply a visual method, called the anchor-based MIC distribution method, which integrates both approaches.

METHOD

Using an anchor, patients are categorized as persons with an important improvement, an important deterioration, or without important change. For these three groups the distribution of the change scores on the health status instrument are depicted in a graph. We present two cut-off points for an MIC: the ROC cut-off point and the 95% limit cut-off point.

RESULTS

We illustrate our anchor-based MIC distribution method determining the MIC for the Pain Intensity Numerical Rating Scale in patients with low back pain, using two conceivable definitions of minimal important change on the anchor. The graph shows the distribution of the scores of the health status instrument for the relevant categories on the anchor, and also the consequences of choosing the ROC cut-off point or the 95% limit cut-off point.

DISCUSSION

The anchor-based MIC distribution method provides a general framework, applicable to all kind of anchors. This method forces researchers to choose and justify their choice of an appropriate anchor and to define minimal importance on that anchor. The MIC is not an invariable characteristic of a measurement instrument, but may depend, among other things, on the perspective from which minimal importance is considered and the baseline values on the measurement instrument under study. A balance needs to be struck between the practicality of a single MIC value and the validity of a range of MIC values.

Minimally important change determined by a visual method integrating an anchor-based and a distribution-based approach

Background:

Minimally important changes (MIC) in scores help interpret results from health status instruments. Various distribution-based and anchor-based approaches have been proposed to assess MIC.

Objectives:

To describe and apply a visual method, called the anchor-based MIC distribution method, which integrates both approaches.

Method:

Using an anchor, patients are categorized as persons with an important improvement, an important deterioration, or without important change. For these three groups the distribution of the change scores on the health status instrument are depicted in a graph. We present two cut-off points for an MIC: the ROC cut-off point and the 95% limit cut-off point.

Results:

We illustrate our anchor-based MIC distribution method determining the MIC for the Pain Intensity Numerical Rating Scale in patients with low back pain, using two conceivable definitions of minimal important change on the anchor. The graph shows the distribution of the scores of the health status instrument for the relevant categories on the anchor, and also the consequences of choosing the ROC cut-off point or the 95% limit cut-off point.

Discussion:

The anchor-based MIC distribution method provides a general framework, applicable to all kind of anchors. This method forces researchers to choose and justify their choice of an appropriate anchor and to define minimal importance on that anchor. The MIC is not an invariable characteristic of a measurement instrument, but may depend, among other things, on the perspective from which minimal importance is considered and the baseline values on the measurement instrument under study. A balance needs to be struck between the practicality of a single MIC value and the validity of a range of MIC values.

Defining the clinical improvement in cancer drug therapy: implications for priority setting in healthcare

An explicit approach to funding decisions has become increasingly important to ensure fairness and consistency in resource allocation in cancer therapy. Funding decisions are often based on whether a treatment is 'medically necessary' and the level of clinical improvement. Currently, there is a lack of consensus on defining different levels of clinical improvement, leading to controversies on the values placed on different outcomes and degrees of clinical improvements during funding evaluation. More information on how clinicians and patients define the levels of clinical improvement can help ensure the evaluation and decision-making processes of funding to become more predictable, consistent, understandable and therefore accountable to providers and consumers of healthcare.

Minimally important difference in diffuse systemic sclerosis: results from the D-penicillamine study

OBJECTIVE

To estimate minimally important differences (MIDs) in scores for the modified Rodnan Skin Score (mRSS) and Health Assessment Questionnaire-Disability Index (HAQ-DI) in a clinical trial on diffuse systemic sclerosis (SSc).

PARTICIPANTS AND METHODS

134 people participated in a 2-year, double-blind, randomised clinical trial comparing efficacy of low-dose and high-dose D-penicillamine in diffuse SSc. At 6, 12, 18 and 24 months, the investigator was asked to rate the change in the patient's health since entering the study: markedly worsened, moderately worsened, slightly worsened, unchanged, slightly improved, moderately improved or markedly improved. Patients who were rated as slightly improved were defined as the minimally changed subgroup and compared with patients rated as moderately or markedly improved.

RESULTS

The MID estimates for the mRSS improvement ranged from 3.2 to 5.3 (0.40-0.66 effect size) and for the HAQ-DI from 0.10 to 0.14 (0.15-0.21 effect size). Patients who were rated to improve more than slightly were found to improve by 6.9-14.2 (0.86-1.77 effect size) on the mRSS and 0.21-0.55 (0.32-0.83 effect size) on the HAQ-DI score.

CONCLUSION

MID estimates are provided for improvement in the mRSS and HAQ-DI scores, which can help in interpreting clinical trials on patients with SSc and be used for sample size calculation for future clinical trials on diffuse SSc.

Estimating sample size in critical care clinical trials

Estimating the required sample size for a study is necessary during the design phase to ensure that it will have maximal efficiency to answer the primary question of interest. Clinicians require a basic understanding of the principles underlying sample size calculation to interpret and apply research findings. This article reviews the critical components of sample size calculation, including the selection of a primary outcome, specification of the acceptable types I and II error rates, identification of the minimal clinically important difference, and estimation of the error associated with measuring the primary outcome. The relationship among confidence intervals, precision, and study power is also discussed.

Sufficiently Important Difference: Expanding the Framework of Clinical Significance

Background. It is generally agreed that randomized controlled trials should be powered to detect small but clinically significant treatment effects. Toward these ends, minimal important difference (MID) was proposed as a benchmark for designing trials and for interpreting health-related quality-of-life instrument scores. MID was defined in 1989 as “the smallest difference in score in the domain of interest which patients perceive as beneficial and which would mandate, in the absence of troubling side effects and excessive cost, a change in the patient’s management.” Objective. 1) To expand the idea of minimal clinically important difference so as to take into account harms as well as benefits. 2) To propose concepts and methods with which to do so. Summary. The authors define sufficiently important difference (SID) as the smallest amount of patient-valued benefit that an intervention would require to justify associated costs, risks, and other harms. As a means toward estimation of SID, the authors propose benefit-harm tradeoff methods, in which domains of benefit and harm are systematically traded off against each other and assessed in relation to the global decision of whether a treatment choice is worthwhile. Specific SID estimates can be used to power and interpret clinical trials or to inform health services research and/or public health policy. This article briefly describes the evolution of the important difference concept and outlines similarities and differences between MID and SID.

Quality of life in patients with bipolar I depression: data from 920 patients

OBJECTIVE

To determine the impact of acute depression on quality of life (QOL) in patients with bipolar I disorder and to compare these results with published data on QOL in patients with unipolar depression.

METHODS

Quality of life was assessed using the SF-36 in bipolar patients (n = 958) who had recently experienced an episode of acute bipolar depression and participated in a large randomized, double-blind, safety and efficacy trial. Seven studies that included SF-36 data from patients with unipolar depression were identified in the published literature and descriptive comparisons of SF-36 scores were made between the unipolar depression trials and this bipolar depression trial.

RESULTS

There were 920 patients who completed the SF-36. Mean transformed scores, which could range from 0 to 100, were very low in bipolar depressed patients for the role-physical (36.7), vitality (22.4), social functioning (29.9), role-emotion (11.4), and mental health (31.0) subscales. Mean SF-36 scores for all subscales were significantly and inversely correlated (p < 0.0001) with the HAM-D indicating that patients with milder depressive symptoms had better QOL. Further, the mean SF-36 scores for the bipolar sample were consistently lower compared with published data on QOL in unipolar depression on four of the eight subscales: general health; social functioning; role-physical, and role-emotional.

CONCLUSIONS

While both unipolar and bipolar depression have serious detrimental effects on patient QOL, our results suggest that some aspects of QOL may be worse in bipolar depression.

Impact of indinavir on the quality of life in patients with advanced HIV infection treated with zidovudine and lamivudine

OBJECTIVE

In AIDS Clinical Trial Group (ACTG) study 320, triple-combination antiretroviral therapy including indinavir significantly slowed progression to acquired immunodeficiency syndrome or death, compared with treatment with dual nucleoside reverse-transcriptase inhibitors (NRTIs) alone, in zidovudine-experienced patients with advanced human immunodeficiency virus (HIV) infection. We examined the impact of indinavir on quality of life in participants from this study.

METHODS

A total of 1156 protease inhibitor- and lamivudine-naive patients stratified by CD4 cell count (<or=50 and 51-200 cells/mm(3)) were randomized to receive zidovudine (or stavudine) and lamivudine, with or without indinavir. Health-related quality of life was measured using the ACTG QoL601-602 questionnaire, which assesses general health status measured on a visual analogue scale and 8 specific health-related domains. Quality-adjusted survival time was estimated using the visual analogue scale for general health.

RESULTS

Mean changes in general health scores after 24 weeks were +2.9 in the triple-therapy group versus -0.2 in the dual-therapy group (P=.018). By week 24, scores in all specific domains were higher with triple-drug therapy than dual-drug therapy, with statistically significant differences in role function, energy, and pain scores. Benefits of triple-drug therapy were largely confined to patients with CD4 cell counts of <or=50 cells/mm(3). Quality-adjusted survival time did not differ significantly between the 2 treatment groups.

CONCLUSIONS

Triple-drug therapy with indinavir and 2 NRTIs resulted in a significant improvement in general health status after 24 weeks, especially in patients with low CD4 cell counts. Patients receiving triple-drug therapy also had significantly better role function, energy, and pain scores than did patients treated with dual-drug therapy.

How much is enough and who says so? The case of the King's Health Questionnaire and overactive bladder

BACKGROUND

One of the challenges of health-related quality of life research is to translate statistically significant health-related quality of life changes into interpretable clinical or medically important ones.

OBJECTIVE

To calculate the minimal important difference of the King's Health Questionnaire, a condition-specific health-related quality of life questionnaire for the assessment of men and women with lower urinary tract dysfunction.

METHODS

The King's Health Questionnaire was administered to patients suffering from overactive bladder enrolled in two multinational studies. Minimal important differences were calculated using an anchor-based approach with both a global rating of patient-perceived treatment benefit and one of perceived disease impact. A distribution-based method using effect size was calculated for comparison purposes.

RESULTS

Minimal important difference values varied slightly with each method. Using the anchor-based approach, the King's Health Questionnaire minimal important difference ranged between 5-10 points when the calculation factored out patients who reported no change and 6-12 points for patients who experienced a small improvement. The effect size method indicated a minimal important difference of 5 to 6 points for a small effect and 10 to 15 points for a medium effect.

CONCLUSIONS

In the case of the King's Health Questionnaire, the anchor-based approaches and the distribution-based approach provide similar results. A change from baseline of at least 5 points on King's Health Questionnaire domains indicates a change that is meaningful to patients and is indicative of a clinically meaningful improvement in health-related quality of life after treatment. Convergence of the estimates using different approaches should give us confidence in the values derived for the quality of life domains measured by the King's Health Questionnaire.

Effects of estrogen plus progestin on health-related quality of life

BACKGROUND

The Women's Health Initiative (WHI) and other clinical trials indicate that significant health risks are associated with combination hormone use. Less is known about the effect of hormone therapy on health-related quality of life.

METHODS

The WHI randomly assigned 16,608 postmenopausal women 50 to 79 years of age (mean, 63) with an intact uterus at base line to estrogen plus progestin (0.625 mg of conjugated equine estrogen plus 2.5 mg of medroxyprogesterone acetate, in 8506 women) or placebo (in 8102 women). Quality-of-life measures were collected at base line and at one year in all women and at three years in a subgroup of 1511 women.

RESULTS

Randomization to estrogen plus progestin resulted in no significant effects on general health, vitality, mental health, depressive symptoms, or sexual satisfaction. The use of estrogen plus progestin was associated with a statistically significant but small and not clinically meaningful benefit in terms of sleep disturbance, physical functioning, and bodily pain after one year (the mean benefit in terms of sleep disturbance was 0.4 point on a 20-point scale, in terms of physical functioning 0.8 point on a 100-point scale, and in terms of pain 1.9 points on a 100-point scale). At three years, there were no significant benefits in terms of any quality-of-life outcomes. Among women 50 to 54 years of age with moderate-to-severe vasomotor symptoms at base line, estrogen and progestin improved vasomotor symptoms and resulted in a small benefit in terms of sleep disturbance but no benefit in terms of the other quality-of-life outcomes.

CONCLUSIONS

In this trial in postmenopausal women, estrogen plus progestin did not have a clinically meaningful effect on health-related quality of life.

Determination of the clinical importance of study results

Formal statistical methods for analyzing clinical trial data are widely accepted by the medical community. Unfortunately, the interpretation and reporting of trial results from the perspective of clinical importance has not received similar emphasis. This imbalance promotes the historical tendency to consider clinical trial results that are statistically significant as also clinically important, and conversely, those with statistically insignificant results as being clinically unimportant. In this paper, we review the present state of knowledge in the determination of the clinical importance of study results. This work also provides a simple, systematic method for determining the clinical importance of study results. It uses the relationship between the point estimate of the treatment effect (with its associated confidence interval) and the estimate of the smallest treatment effect that would lead to a change in a patient's management. The possible benefits of this approach include enabling clinicians to more easily interpret the results of clinical trials from a clinical perspective, and promoting a more rational approach to the design of prospective clinical trials.

Comparison of three active therapies for chronic low back pain: results of a randomized clinical trial with one-year follow-up

OBJECTIVES

To examine the relative efficacy of three active therapies for patients with chronic low back pain.

METHODS

One hundred and forty-eight subjects with chronic low back pain were randomized to receive, twice weekly for 3 months, (i) active physiotherapy, (ii) muscle reconditioning on training devices, or (ii) low-impact aerobics. Questionnaires were administered to assess pain intensity, pain frequency and disability before and after therapy and at 6 and 12 months of follow-up.

RESULTS

One hundred and thirty-two of the 148 patients (89%) completed the therapy programmes and 127 of the 148 (86%) returned a questionnaire at all four time-points. The three treatments were equally efficacious in significantly reducing pain intensity and frequency for up to 1 yr after therapy. However, the groups differed with respect to the temporal changes in self-rated disability over the study period (P=0.03): all groups showed a similar reduction after therapy, but for the physiotherapy group disability increased again during the first 6 months of follow-up whilst the other two groups showed a further decline. In all groups the values then remained stable up to the 12-month follow-up. The larger group size and minimal infrastructure required for low-impact aerobics rendered it considerably less expensive to administer than the other two programmes.

CONCLUSIONS

The introduction of low-impact aerobic exercise programmes for patients with chronic low back pain may reduce the enormous costs associated with its treatment.

The RAND-36 measure of health-related quality of life

The RAND-36 is perhaps the most widely used health-related quality of life (HRQoL) survey instrument in the world today. It is comprised of 36 items that assess eight health concepts: physical functioning, role limitations caused by physical health problems, role limitations caused by emotional problems, social functioning, emotional well-being, energy/fatigue, pain, and general health perceptions. Physical and mental health summary scores are also derived from the eight RAND-36 scales. This paper provides example applications of the RAND-36 cross-sectionally and longitudinally, provides information on what a clinically important difference is for the RAND-36 scales, and provides guidance for summarizing the RAND-36 in a single number. The paper also discusses the availability of the RAND-36 in multiple languages and summarizes changes that are incorporated in the latest version of the survey.

Defining the clinically important difference in pain outcome measures

The purpose of this study was to determine the levels of change on standard pain scales that represent clinically important differences to patients. Data from analgesic studies are often difficult to interpret because the clinical importance of the results is not obvious. Differences between groups, as summarized by a change in mean values over time, can be difficult to apply to clinical care. Baseline scores vary widely and group mean differences could reflect large changes in a few patients, small changes in many patients, or any combination of these outcomes. Determination of the proportion of patients who have a clinically important improvement in their pain would provide a more interpretable result with direct clinical implications. However, determining a clinically important outcome requires information about the degree of change over time that is clinically important. Data from the titration phase of a multiple cross-over randomized clinical trial of oral transmucosal fentanyl citrate (OTFC) for the treatment of cancer-related breakthrough pain were re-analyzed to examine the differences in pain scores between treatment episodes that did and did not yield adequate pain relief. The scales evaluated were absolute pain intensity difference (PID, 0-10 scale), percentage pain intensity difference (PID%, 0-100% scale), pain relief (PR, 0 (none), 1 (slight), 2 (moderate), 3 (lots), 4 (complete)), sum of the pain intensity difference (SPID over 60 min), percentage of maximum total pain relief (% Max TOTPAR over 60 min), and global medication performance (0 (poor), 1 (fair), 2 (good), 3 (very good), 4 (excellent)). Adequate relief was defined by the patient's decision not to use another dose of opioid medication as a rescue, in addition to the study medication, to treat each painful episode. One hundred thirty OTFC naive patients contributed data on 1268 episodes of breakthrough pain. The scales that were converted to a percentage change yielded the best accuracy in predicting adequate relief, with balanced sensitivity and specificity. The best cut-off point for both the % Max TOTPAR and the PID% was 33%. The best cut-off points for the absolute scales were absolute pain intensity difference of 2, pain relief of 2 (moderate), and SPID of 2. The global medication performance of 2 (good) had excellent values as well. This study presents data-derived cut-off points for the changes in several pain scales, each reflecting the clinically important improvement for patients treating breakthrough cancer pain episodes with OTFC. Confirmation in other patient populations and different pain syndromes will be needed. The use of consistent clinically important cut-off points as the primary outcome in future pain therapy clinical trials will enhance their validity, comparability, and clinical applicability.

The concept of clinically meaningful difference in health-related quality-of-life research. How meaningful is it?

It is generally believed that small differences in health-related quality of life (HR-QOL) may be statistically significant yet clinically unimportant. The concept of the minimal clinically meaningful difference (MCID) has been proposed to refer to the smallest difference in a HR-QOL score that is considered to be worthwhile or clinically important. However, there is danger in oversimplification in asking the question: what is the MCID on this HR-QOL instrument? We argue that the attempt to define a single MCID is problematic for a number of reasons and recommend caution in the search for the MCID holy grail. Specifically, absolute thresholds are suspect because they ignore the cost or resources required to produce a change in HR-QOL. In addition, there are several practical problems in estimating the MCID, including: (i) the estimated magnitude varies depending on the distributional index and the external standard or anchor; (ii) the amount of change might depend on the direction of change; and (iii) the meaning of change depends on where you start (baseline value).