Evaluation of the effect of non-surgical periodontal treatment on oral health-related quality of life: estimation of minimal important differences 1 year after treatment. Sufficiently Important Difference: Expanding the Framework of Clinical Significance Minimally important differences of the gout impact scale in a randomized controlled trial. Evaluating clinically meaningful change on the ITP-PAQ: preliminary estimates of minimal important differences. Assessing the clinical significance of health-related quality of life (HrQOL) improvements in anaemic cancer patients receiving epoetin alfa. Minimally Important Differences of the UCLA Scleroderma Clinical Trial Consortium Gastrointestinal Tract Instrument Using multiple anchor- and distribution-based estimates to evaluate clinically meaningful change on the Functional Assessment of Cancer Therapy-Biologic Response Modifiers (FACT-BRM) instrument. Assessing the minimally important difference in the oral impact on daily performances index in patients treated for periodontitis. Use of the modified SNOT-16 in primary care patients with clinically diagnosed acute rhinosinusitis. Comparison of distribution- and anchor-based approaches to infer changes in health-related quality of life of prostate cancer survivors. A prospective global measure, the Punum Ladder, provides more valid assessments of quality of life than a retrospective transition measure. Three methods for minimally important difference: no relationship was found with the net proportion of patients improving. Secukinumab treatment in rheumatoid arthritis is associated with incremental benefit in the clinical outcomes and HRQoL improvements that exceed minimally important thresholds Health-related quality of life in patients with advanced renal cell carcinoma receiving pazopanib or placebo in a randomised phase III trial. Using the standard error of measurement to identify important changes on the Asthma Quality of Life Questionnaire Evaluation of the minimal important difference for the feeling thermometer and the St. George's Respiratory Questionnaire in patients with chronic airflow obstruction. Asthma symptom utility index: reliability, validity, responsiveness, and the minimal important difference in adult asthmatic patients. Interpreting changes in quality-of-life score in N of 1 randomized trials.
AIM To evaluate an individually tailored oral health educational programme on patient-reported outcome compared with a st and ard oral health educational programme , assess change over time and determine minimal important differences ( MID ) in change scores for two different oral health related quality of life ( OHRQoL ) instrument after non-surgical periodontal treatment ( NSPT ) . MATERIAL S AND METHODS In a r and omized controlled trial evaluating two educational programmes , patients ( n = 87 ) with chronic periodontitis completed a question naire at baseline and after 12 months . OHRQoL was assessed with the General Oral Health Assessment Index ( GOHAI ) and the UK oral health-related quality -of-life measure ( OHQoL-UK ) . In addition , patients ' global rating of oral health and socio-demographic variables were recorded . The MID was estimated with anchor-based and distributions-based methods . RESULTS There were no differences between the two educational groups . The OHRQoL was significantly improved after treatment . The MID was approximately five for OHQoL-UK with a moderate ES , and three for GOHAI with a Small ES , and 46 - 50 % of the patients showed improvements beyond the MID . CONCLUSION Both oral health educational groups reported higher scores in OHRQoL after NSPT result ing in more positive well-being ( OHQoL-UK ) and less frequent oral problems ( GOHAI ) . OHQoL-UK gave a greater effect size and mean change scores but both instruments were associated with the participants ' self-rated change in oral health . The changes were meaningful for the patients supported by the estimated MID Background . It is generally agreed that r and omized controlled trials should be powered to detect small but clinical ly significant treatment effects . Toward these ends , minimal important difference ( MID ) was proposed as a benchmark for design ing 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 m and ate , in the absence of troubling side effects and excessive cost , a change in the patient ’s management . ” Objective . 1 ) To exp and the idea of minimal clinical ly 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 systematic ally 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 OBJECTIVE The Gout Impact  Scale ( GIS ) is a gout-specific quality of life instrument that assesses impact of gout during an attack and impact of overall gout . The GIS has five scales and each is scored from 0 to 100 ( worse health ) . Our objective was to assess minimally important differences ( MIDs ) for the GIS administered in a r and omized controlled trial ( RCT ) assessing rilonacept vs placebo for prevention of gout flares during initiation of allopurinol therapy . METHODS Trial subjects ( n = 83 ) included those with two or more gout flares ( self-reported ) in the past year . Of these , 73 had data for Weeks 8 vs 4 and formed the MID analysis group and were analysed irrespective of the treatment assignment . Subjects completed the GIS and seven patient-reported anchors . Subjects with a one-step change ( e.g. from very poor to poor ) were considered as the MID group for each anchor . The mean change in GIS scores and effect size ( ES ) was calculated for each anchor 's MID group . The average of these created the overall summary MID statistics for each GIS . An ES of 0.2 - 0.5 was considered to represent MID estimates . Results . Trial subjects ( n = 73 ) were males ( 96.0 % ) , White ( 90.4 % ) , with mean age of 50.5 years and serum uric acid of 9.0 mg/dl . The mean change score for the MID improvement group for scales ranged from -5.24 to -7.61 ( 0 - 100 scale ) . The ES for the MID improvement group for the four scales ranged from 0.22 to 0.38 . CONCLUSION The MID estimates for GIS scales are between 5 and 8 points ( 0 - 100 scale ) . This information can aid in interpreting the GIS results in future gout RCTs . Trial Registration . Clinical trials.gov , www . clinical trials.gov , NCT00610363 OBJECTIVE Interpretation of data from health-related quality of life ( HRQoL ) question naires can be enhanced with the availability of minimally important difference ( MID ) estimates . This information will aid clinicians in interpreting HRQoL differences within patients over time and between treatment groups . The Immune Thrombocytopenic Purpura (ITP)-Patient  Assessment Question naire ( PAQ ) is the only comprehensive HRQoL question naire available for adults with ITP . RESEARCH DESIGN AND METHODS Forty centers from within the US and Europe enrolled ITP patients into one of two multicenter , r and omized , placebo-controlled , double-blind , 6-month , phase III clinical trials of romiplostim . Patients enrolled in these studies self-administered the ITP-PAQ and two items assessing global change ( anchors ) at baseline and weeks 4 , 12 , and 24 . Using data from the ITP-PAQ and these two anchors , an anchor-based estimate was computed and combined with the st and ard error of measurement and st and ard deviation to compute a distribution-based estimate in order to provide an MID range for each of the 11 scales of the ITP-PAQ . RESULTS A total of 125 patients participated in these clinical trials and provided data for use in these analyses . Combining results from anchor- and distribution-based approaches , MID values were computed for 9 of the 11 scales . MIDs ranged from 8 to 12 points for Symptoms , Bother , Psychological , Overall QOL , Social Activity , Menstrual Symptoms , and Fertility , while the range was 10 to 15 points for the Fatigue and Activity scales of the ITP-PAQ . These estimates , while slightly higher than other published MID estimates , were consistent with moderate effect sizes . CONCLUSIONS These MID estimates will serve as a useful tool to research ers and clinicians using the ITP-PAQ , providing guidance for interpretation of baseline scores as well as changes in ITP-PAQ scores over time . Additional work should be done to finalize these initial estimates using more appropriate anchors that correlate more highly with the ITP-PAQ scales Health-related quality of life ( HrQOL ) assessment s are gaining importance as outcome measures in cancer clinical trials . A recently published clinical trial reported statistically significant ( P<0.001 ) increases in haemoglobin ( Hb ) levels and significantly ( P<0.01 ) increased HrQOL scores following the administration of recombinant human erythropoietin ( r-HuEPO , epoetin alfa ) versus placebo to anaemic cancer patients who received non-platinum chemotherapy . This study employed five cancer-specific HrQOL instruments . Hb and HrQOL data from this trial were analysed to estimate the minimally important difference ( MID ) in HrQOL measures that could be interpreted as clinical ly meaningful , with Hb level selected as the best external st and ard . Patients were assigned to two groups : improved ( Hb increases of > /=1 g/dL ) or stable ( change in Hb of-1 g/dL to < 1 g/dL ) . The MID was first determined as the difference between the mean changes in HrQOL in the improved group versus the stable group . By this analysis , the differences in HrQOL scores between the epoetin alfa group and the placebo group were clinical ly important for all Hb-sensitive , cancer-specific HrQOL evaluations . Linear regression analyses performed to provide estimates of the MID for specific values of Hb change confirmed that the differences in HrQOL scores between patient groups were clinical ly significant . These analyses were repeated using a data set from a separate clinical trial , which further supported the conclusion that observed HrQOL changes demonstrated in the multicentre , double-blind study were clinical ly important . These methods provide one means for interpreting the clinical relevance of changes in HrQOL evaluated in clinical trials Objective . To provide minimally important difference ( MID ) estimates for the UCLA Scleroderma Clinical Trial Consortium Gastrointestinal Tract 2.0 ( UCLA SCTC GIT 2.0 ) in a longitudinal observational cohort . Methods . We administered the UCLA SCTC GIT 2.0 to 115 patients with systemic sclerosis ( SSc ) at 2 timepoints 6 months apart . The UCLA SCTC GIT 2.0 has 7 multi-item scales : Reflux , Distension/Bloating , Diarrhea , Fecal Soilage , Constipation , Emotional Well-being , and Social Functioning and a total GIT score . All scales are scored from 0 [ better health-related quality of life ( HRQOL ) ] to 3 ( worse HRQOL ) except the diarrhea and constipation scales ( ranges 0–2 and 0–2.5 , respectively ) . Patients also rated their overall and upper and lower GIT involvement during the second visit using a response scale with options “ much better ; somewhat better ; almost the same ; somewhat worse ; or much worse . ” The minimally changed group was defined by those reporting they were somewhat better or somewhat worse compared to first visit . Results . Study participants were 84 % female and 81 % white with a mean disease duration of 6.9 years . The MID estimates for improvement ranged from 0.07 for the Social Functioning scale to 0.36 for the Emotional Well-being scale . For worsening , the MID estimates ranged from 0.06 for the Fecal Soilage scale to 0.21 for the Social Functioning scale . Conclusion . We provide MID estimates for the UCLA SCTC GIT 2.0 scales . This information can aid in interpreting scale scores in future r and omized controlled trials and observational studies OBJECTIVE The interpretation of health-related quality of life ( HRQL ) data from clinical trials can be enhanced by underst and ing the degree of change in HRQL scores that is considered meaningful . Our objectives were to combine distribution-based and two anchor-based approaches to identify minimally important differences ( MIDs ) for the 27-item Trial Outcome Index ( TOI ) , the seven-item Social Well-Being ( SWB ) subscale , and the six-item Emotional Well-being ( EWB ) subscale from the Functional Assessment of Cancer Therapy-Biological Response Modifiers ( FACT-BRM ) instrument . METHODS Distribution-based MIDs were based on the st and ard error of measurement . Anchor-based approaches utilized  patient-reported global rating of change ( GRC ) and change in physician-reported performance status rating ( PSR ) .  Correlations and weighted kappa statistics were used to assess association and agreement between the two anchors . FACT-BRM changes were evaluated for three time periods : baseline to month 1 , month 2 to month 3 , and month 5 to month 6 . RESULTS Association between GRC and change in PSR was poor . Correlation between the anchors and HRQL change scores was largest at month 1 and decreased through month 6 . Combining results from all approaches , the MIDs identified were 5 - 8 points for the TOI , 2 points for the SWB subscale , and 2 - 3 points for the EWB subscale . CONCLUSIONS We combined patient-reported estimates , physician-reported estimates , and distribution-based estimates to derive MIDs for HRQL outcomes from the FACT-BRM . These results will enable interpretation of treatment group effects in a clinical trial setting , and they can be used to estimate sample size or power when design ing future studies AIM To assess changes over time and determine the minimally important difference ( MID ) in the Oral Impact on Daily Performances ( OIDP ) index for patients with severe generalized periodontitis receiving periodontal treatment .  METHODS This study was nested in a larger r and omized controlled trial and consisted of 45 consecutive subjects of the larger trial ( 17 receiving intensive and 28 receiving conservative periodontal care ) . The OIDP index assessed impacts on quality of life ( QoL ) at baseline and 1 month after treatment . Repeated- measures ANOVA was used for comparison over time and between treatment groups . To estimate the MID , two subjective global transition scales , related to periodontal and oral health , respectively , were used as anchors , whereas the effect size ( ES ) , st and ardized response mean and st and ard error of measurement were also calculated . RESULTS The mean OIDP score after treatment was significantly lower than at baseline , indicating improvement in QoL , but there were no differences between treatment groups . Based on an agreement between different methods , the MID of the OIDP index was around five scale points and corresponded to a moderate ES . CONCLUSION The MID for the OIDP index among patients treated for severe generalized periodontitis provides meaning to change scores and facilitates interpretation of findings OBJECTIVE To determine the reliability , validity , responsiveness , and the minimal important difference ( MID ) for the Sinonasal Outcome Test-16 ( SNOT-16 ) in the measurement of disease-specific quality of life ( QOL ) in adults with acute rhinosinusitis . STUDY DESIGN R and omized controlled trial to evaluate antibiotic treatment for acute rhinosinusitis . SETTING Ten community practice s in St Louis , Missouri . METHODS The modified SNOT-16 was completed at baseline ( by both face-to-face and telephone interviews ) and by telephone interview at 3 , 7 , and 10 days by 166 adults with acute rhinosinusitis diagnosed clinical ly using st and ardized criteria ( 36 % were male , 78 % were white ) . Considering severity and frequency , patients rated how much they were bothered by each item using a 4-point scale . The mean SNOT-16 score ( ranging from 0 [ no problem ] to 3 [ large problem ] ) was compared with the patients ' global assessment of change to evaluate responsiveness and the MID . RESULTS The instrument was easy to use and took less than 5 minutes to complete . The SNOT-16 score identified statistically significant differences in the hypothesized direction for those reporting more or less severe symptoms ( P = .02 ) and more or less bother ( P < .001 ) demonstrating construct-related validity . The Cronbach α ranged from 0.82 to 0.91 , demonstrating high internal consistency . There was a statistically significant decrease in scores with time ( multivariate analysis of variance , P < .001 ) . The effect sizes at days 3 , 7 , and 10 were 1.45 , 2.34 , and 2.90 , respectively , indicating high sensitivity to clinical change . The MID was 0.5 units . CONCLUSION The modified SNOT-16 is a valid instrument to assess effectiveness of interventions to improve disease-specific QOL  in adults with acute rhinosinusitis . TRIAL REGISTRATION clinical trials.gov Identifier : NCT00377403 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 Prospect i ve 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 OBJECTIVES We assessed the reliability and validity of two measures of change , one retrospective ( the Global Rating of Change Scale [ GRCS ] ) and one prospect i ve ( the Punum Ladder ) , and the relative utility of the two methods of assessing change and establishing the minimal important difference ( MID ) of the Cough Quality of Life Question naire ( CQLQ ) , a reliable and valid cough-specific quality -of-life ( QoL ) instrument . STUDY DESIGN AND SETTING A prospect i ve , longitudinal study assessing the change in cough-related QoL over 6 months in participants with chronic cough was carried out in a tertiary care cough clinic . Before seeing a physician , subjects completed eight Punum Ladders and the CQLQ . At 1 and 6 months , eight Punum Ladders , the CQLQ , and seven GRCSs were completed . Punum Ladders and GRCSs were psychometrically tested , and MIDs were calculated . RESULTS Reliability and validity of GRCSs and Punum Ladders were acceptable . However , closer analysis of the relation between change scores and  CQLQ pretest and posttest scores showed that the GRCS was only related to patient 's present state , whereas the Punum Ladder was associated with both initial and present states . This compromises the validity of the GRCS . Crosstab comparisons revealed that GRCS ratings made more liberal estimates of change in the CQLQ than the Punum Ladder ; this is reflected in their respective MIDs ( 10.58+/-10.63 vs. 21.89+/-15.38 ) . CONCLUSION The prospect i ve Punum Ladder is likely to be more useful , because it reflects the actual change in QoL over time in a less biased and more accurate way than the retrospective GRCS OBJECTIVE To determine the impact on a responder type analysis of using three published methods to obtain the minimally important difference ( MID ) on the conclusion of a r and omized controlled trial ( RCT ) . STUDY DESIGN AND SETTING Using data from an RCT of supportive-expressive group therapy ( SEGT-intervention ) vs. st and ard care ( control ) in women with metastatic breast cancer , we measured individual responsiveness to change according to three levels of predefined MID ( 0.2 SD , 0.5 SD , and 1 st and ard error of measurement ) of the following six vali date d question naires : Profile of Mood States , Impact of Event Scale , Psychosocial Adjustment to Illness Scale , EORTC Quality -of-Life Question naire Core-30 , Mental Adjustment to Cancer , and a pain visual analog scale . The proportion of women improved by SEGT  and the number needed to treat according to three levels of MID were calculated . RESULTS There was no consistent difference in the net proportion of women improving with the SEGT vs. control arm according to the three different levels of MID . CONCLUSION The choice between different levels of distribution-based MID did not make an important difference in the net proportion of women improving with the SEGT . Future research should compare MID derived from clinical anchors , in particular patient opinions Background The primary aim of rheumatoid arthritis ( RA ) treatment is to induce remission , the absence of disease activity . The objective of this study was to explore the association between clinical endpoints used to gauge RA treatment efficacy and patient-reported outcomes of health-related quality of life , fatigue , and physical function in RA patients treated with secukinumab in a phase 2 r and omized controlled trial ( RCT ) . Method Adult RA patients ( n = 237 ) with incomplete responses to methotrexate were r and omized equally to receive monthly s.c . injections of secukinumab 25 mg , 75 mg , 150 mg , 300 mg or placebo . Clinical endpoints used in this study included the ACR response criteria and its components and simplified disease activity score . Patient-reported outcomes ( PRO ) included Health Assessment Question naire-Disability Index ( HAQ-DI ) , Medical Outcomes Study Short Form-36 [ SF-36 ] Survey , and Functional Assessment of Chronic Illness Therapy-Fatigue ( FACIT-Fatigue ) . Patients were categorized into mutually exclusive groups according to the magnitude and direction of change from baseline to week 16 in each clinical endpoint . Definitions of minimal important differences [ MID ] in each clinical endpoint were used to categorize patients , as well as thresholds beyond MID . Mean changes from baseline to week 16 were computed for each PRO and analyses of variance to test the differences in PRO changes observed across groups of patients that differed in each clinical endpoint . Analyses were limited to patients r and omized to secukinumab treatment . All dose groups were combined ( n = 187 ) . Results Mean changes from baseline in each PRO differed significantly across groups of patients in the expected direction . With few exceptions , there was considerable agreement between clinical endpoints and PROs concerning the magnitude of change defined as clinical ly meaningful . More importantly , results demonstrated that greater improvements in clinical endpoints were associated with incrementally better improvements in HRQoL , fatigue , and physical function . Conclusion Results of this study show considerable agreement between minimal thresholds of improvement established for PROs and clinical outcome measures used in RA treatment studies and provide thresholds to be considered in gauging the importance of a treatment effect that goes beyond what is considered as minimally important for PRO measures BACKGROUND In a double-blind , r and omised phase III trial of advanced renal cell carcinoma patients  , pazopanib 800 mg QD ( n=290 ) versus placebo ( n=145 ) significantly prolonged progression-free survival ( hazard ratio (HR)=0.46 , 95 % confidence interval [ CI ] 0.34 - 0.62 , p-value<0.0001 ) , without important differences in health-related quality of life ( HRQoL ) . This post-hoc analysis evaluated time to HRQoL deterioration and whether tumour response/stabilisation was associated with HRQoL improvement . METHODS HRQoL was assessed using EORTC QLQ-C30 and EQ-5D . Effect of pazopanib on time to ⩾20 % decline from baseline in summary scores was estimated for all patients and by prior treatment . Analyses were conducted for different HRQoL deterioration thresholds . HRQoL changes were stratified by benefit and compared : complete response ( CR ) or partial response ( PR ) versus progressive disease ( PD ) ; CR/PR versus stable disease ( SD ) , and SD versus PD . RESULTS There was a trend for pazopanib patients to be less likely than placebo patients to experience ⩾20 % HRQoL deterioration in EORTC-QLQ-C-30 global health status/QOL scale ( HR=0.77 ; 95 % CI 0.57 - 1.03 , not significant ) . Results by prior treatment and different HRQoL deterioration thresholds were similar . Patients with CR/PR and SD experienced significantly less HRQoL deterioration than those with PD ( p<0.001 , p=0.0024 , respectively ) ; mean differences between patients with CR/PR and PD exceeded the pre-determined minimally important difference ( MID ) . Differences between patients with SD and PD did not exceed pre-determined MID . Results were generally consistent across treatment and EQ-5D summary scores . CONCLUSION Results support the favourable benefit-risk profile of pazopanib and suggest patients experiencing tumour response/stabilisation also may have better HRQoL compared to those without this response Objectives : To establish a link between the minimal important difference ( MID ) and the st and ard error of measurement ( SEM ) for all responsive dimensions of the Asthma Quality of Life Question naire ( AQLQ ) . Methods : Secondary data analysis of baseline and follow-up interview data from 198 out patients with asthma enrolled in a r and omized controlled trial and receiving care at a major urban academic medical center 's general medicine clinics . Domain statistics for baseline and follow-up interviews were examined for the AQLQ . The baseline SEM values were compared with established AQLQ MID st and ards using weighted κ values . Results : One SEM identified the MID in responsive AQLQ dimensions . Weighted κ values ( 0.88–0.93 ) vali date d excellent agreement between these two criteria . Conclusion : This is the third study to support using one SEM to identify important individual change in health-related quality of life ( HRQoL ) measures . However , refinement of the process for determining a measure 's clinical ly meaningful differences is still needed to secure a link between the SEM and the identification of relevant HRQoL change over time BACKGROUND / OBJECTIVES The chronic respiratory question naire ( CRQ ) , the St. Georges Respiratory Question naire ( SGRQ ) , and the feeling thermometer ( FT ) evaluate change in health-related quality of life ( HRQL ) in patients with chronic airflow limitation ( CAL ) . Although the interpretability , and in particular the minimal important difference ( MID ) in score changes , is well established for the CRQ , this is not the case for the SGRQ and FT . The objective of our study is to explore the interpretation of the SGRQ and FT . METHODS We analyzed data from 84 patients who completed the CRQ , SGRQ , and FT before beginning pulmonary rehabilitation and 3 months later . We calculated correlations between the four CRQ domains ( dyspnea , fatigue , emotional function , and mastery ) and the three SGRQ domains ( symptoms , activities , and impact ) , the SGRQ total score , and the FT . When Pearson 's correlations were > /=0.5 , we constructed regression equations and used the slope to calculate the change in SGRQ and FT score that corresponded to a change in CRQ score of 0.5 ( the MID ) . Having established MID for SGRQ we than used a similar approach to examine the relation between the SGRQ and FT results . RESULTS Comparison with the CRQ dyspnea domain suggested the MID in SGRQ total score is approximately 3.05 with a 95 % confidence interval ( 95 % CI ) ranging from 0.39 to 5.71 and a change of 5.67 ( 95 % CI 3.43 - 7.92 ) represents a moderate change ( 1.0 on the CRQ dyspnea domain ) . The MID for the FT based on the CRQ fatigue domain was 6.1 ( 95 % CI 1.87 - 10.28 ) . The FT MID based on the SGRQ activities domain , impacts domain , and total score were , respectively , 7.4 ( 95 % CI 3.44 - 11.35 ) , 5.6 ( 95 % CI 1.6 - 9.64 ) , and 5.9 ( 95 % CI 1.97 - 9.78 ) . CONCLUSIONS An MID for the SGRQ approximates the previously suggested estimate of 4 on a scale of 0 to 100 . The MID for the FT in patients with CAL is approximately 5 to 8 units on the 0 to 100 scale . These MID estimates should facilitate interpretation of clinical trials in which outcome measures include the SGRQ or FT BACKGROUND The evaluation of asthma symptoms is a core outcome measure in asthma clinical research . The Asthma Symptom Utility Index ( ASUI ) was developed to assess the frequency and severity of asthma symptoms . The psychometric properties of the ASUI are not well characterized , and a minimal important difference ( MID ) is not established . OBJECTIVES We assessed the reliability , validity , and responsiveness to change of the ASUI in a population of adult asthmatic patients . We also sought to determine the MID for the ASUI . METHODS Adult asthmatic patients ( n = 1648 ) from 2 previously completed multicenter r and omized trials were included .  Demographic information , spirometric results , ASUI scores , and other asthma question naire scores  were obtained at baseline and during follow-up visits . Participants also kept a daily asthma diary . RESULTS The internal consistency reliability of the ASUI was 0.74 ( Cronbach α ) . Test-retest reliability was 0.76 ( intraclass correlation ) . Construct validity was demonstrated by significant correlations between ASUI scores and Asthma Control Question naire scores ( Spearman correlation r = -0.79 ; 95 % CI , -0.85 to -0.75 ; P < .001 ) and Mini Asthma Quality of Life Question naire scores ( r = 0.59 ; 95 % CI , 0.51 - 0.61 ; P < .001 ) . Responsiveness to change was demonstrated , with significant differences between mean changes in ASUI scores across groups of participants differing by 10 % in percent predicted FEV(1 ) ( P < .001 ) and by 0.5 points in Asthma Control Question naire scores ( P < .001 ) . Anchor-based and statistical methods support an MID for the ASUI of 0.09 points . CONCLUSIONS The ASUI is reliable , valid , and responsive to changes in asthma control over time . The MID of the ASUI ( range of scores , 0 - 1 ) is 0.09 To provide additional evidence regarding the plausible range of the differences in health-related quality of life ( HRQL ) question naire scores within which the minimal important difference ( MID ) falls , we review ed the results of 32 r and omized controlled trials in individual subjects ( N of 1 RCTs ) with chronic diseases . These trials had been conducted to establish whether a patient was obtaining more good than harm from a medication . Each N of 1 RCT included a series of pairs of treatment periods , one period on active drug , and one on placebo or alternative drug . We examined the relationship between small ( MID ) , medium , and large differences between periods within pairs , as indicated by Global Ratings and differences between these same periods according to HRQL question naires . The results showed a mean difference of 0.29 points per question in HRQL question naire scores corresponded to the MID . Differences of approximately 0.66 points per question corresponded to a moderate difference as ranked by the Global Rating ; difference of about 1.09 points per question represented marked difference
There was no consistent relationship with factors such as disease-specific or generic instrument or the number of response options .
Negative changes were not associated with larger ESs .
Population -based estimation procedures and brief follow-up were associated with smaller ESs , and acute conditions with larger ESs .
Background .
A number of studies have computed the minimally important difference ( MID ) for health-related quality of life instruments .
To determine whether there is consistency in the magnitude of MID estimates from different instruments .