***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND The recent recognition that coronary-artery stenting has improved the short- and long-term outcomes of patients treated with angioplasty has made it necessary to reevaluate the relative benefits of bypass surgery and percutaneous interventions in patients with multivessel disease . METHODS A total of 1205 patients were r and omly assigned to undergo stent implantation or bypass surgery when a cardiac surgeon and an interventional cardiologist agreed that the same extent of revascularization could be achieved by either technique . The primary clinical end point was freedom from major adverse cardiac and cerebrovascular events at one year . The costs of hospital re sources used were also determined . RESULTS At one year , there was no significant difference between the two groups in terms of the rates of death , stroke , or myocardial infa rct ion . Among patients who survived without a stroke or a myocardial infa rct ion , 16.8 percent of those in the stenting group underwent a second revascularization , as compared with 3.5 percent of those in the surgery group . The rate of event-free survival at one year was 73.8 percent among the patients who received stents and 87.8 percent among those who underwent bypass surgery ( P<0.001 by the log-rank test ) . The costs for the initial procedure were $ 4,212 less for patients assigned to stenting than for those assigned to bypass surgery , but this difference was reduced during follow-up because of the increased need for repeated revascularization ; after one year , the net difference in favor of stenting was estimated to be $ 2,973 per patient . CONCLUSION As measured one year after the procedure , coronary stenting for multivessel disease is less expensive than bypass surgery and offers the same degree of protection against death , stroke , and myocardial infa rct ion . However , stenting is associated with a greater need for repeated revascularization Purpose : We sought to compare directly elicited valuations for EQ-5D health states between the US and UK general adult population s. Methods : We analyzed data from 2 EQ-5D valuation studies where , using similar time trade-off protocol s , values for 42 common health states were elicited from representative sample s of the US and UK general adult population s. First , US and UK population mean valuations were estimated and compared for each health state . Second , r and om-effect models were used to compare the US and UK valuations while adjusting for known predictors of EQ-5D valuations ( ie , age , sex , health state descriptors ) and to investigate whether and how the valuations differ . Results :  Population mean valuations of the 42 health states ranged from −0.38 to 0.88 for the United States and from −0.54 to 0.88 for the United Kingdom , with the US mean scores being numerically higher than the UK for 39 health states ( mean difference : 0.11 ; range : −0.01 to 0.25 ) . After adjusting for the main effects of known predictors , the average difference in valuations was 0.10 ( P < 0.001 ) . The magnitude of the difference in the US and UK valuations was not constant across EQ-5D health states ; greater differences in valuations were present in health states characterized by extreme problems . Conclusions : Meaningful differences exist in directly elicited TTO valuations of EQ-5D health states between the US and UK general population s. Therefore , EQ-5D index scores generated using valuations from the US general population should be used for studies aim ing to reflect health state preferences of the US general public BACKGROUND The SF-6D is a new health state classification and utility scoring system based on 6 dimensions ( ' 6D ' ) of the Short Form 36 , and permits a " bridging " transformation between SF-36 responses and utilities . The Health Utilities Index , mark 3 ( HUI3 ) is a valid and reliable multi-attribute health utility scale that is widely used . We assessed within-subject agreement between SF-6D utilities and those from HUI3 . METHODS Patients at increased risk of sudden cardiac death and participating in a r and omized trial of implantable defibrillator therapy completed both instruments at baseline . Score distributions were inspected by scatterplot and histogram and mean score differences compared by paired t-test . Pearson correlation was computed between instrument scores and also between dimension scores within instruments . Between-instrument agreement was by intra-class correlation coefficient ( ICC ) . RESULTS SF-6D and HUI3 forms were available from 246 patients .  Mean scores for HUI3 and SF-6D were 0.61 ( 95 % CI 0.60 - 0.63 ) and 0.58 ( 95 % CI 0.54 - 0.62 ) respectively ; a difference of 0.03 ( p<0.03 ) . Score intervals for HUI3 and SF-6D were ( -0.21 to 1.0 ) and ( 0.30 - 0.95 ) . Correlation between the instrument scores was 0.58 ( 95 % CI 0.48 - 0.68 ) and agreement by ICC was 0.42 ( 95 % CI 0.31 - 0.52 ) . Correlations between dimensions of SF-6D were higher than for HUI3 . CONCLUSIONS Our study casts doubt on the whether utilities and QALYs estimated via SF-6D are comparable with those from HUI3 . Utility differences may be due to differences in underlying concepts of health being measured , or different measurement approaches , or both . No gold st and ard exists for utility measurement and the SF-6D is a valuable addition that permits SF-36 data to be transformed into utilities to estimate QALYs . The challenge is developing a better underst and ing as to why these classification-based utility instruments differ so markedly in their distributions and point estimates of derived utilities The objective of this study is to evaluate the costs and health benefits of coronary artery bypass grafting ( CABG ) surgery with and without cardiopulmonary bypass ( CPB ) . R and omized controlled clinical trial is used as the design . The setting is in a single tertiary cardiothoracic center in Middlesex , UK . Participants were 168 patients ( 27 females ) requiring primary isolated CABG surgery . Patients were r and omized to have the procedure performed by a single surgeon either with CPB ( n = 84 ) or by an off-pump coronary artery bypass ( OPCAB ) surgery ( n = 84 ) .  Health-related quality of life was assessed at baseline , 6 weeks , and 6 months using the World Health Organization Quality -of-Life ( WHOQOL-100 ) question naire . Mean total costs of patient management by either technique were calculated using different available key sources . A utility measure , derived from WHOQOL-100 , was used to calculate quality -adjusted life year ( QALY ) gained in each group , on basis of which a cost-effectiveness analysis was performed . The mean total costs of an OPCAB patient was 5859 pounds , whereas for a CPB patient it was 7431 pounds with a mean difference of 1572 pounds ( st and ard error [ SE ] 674 pounds ; P = 0.02 ) . Three patients died in the CPB group and two in the OPCAB group during the 6-month follow-up period . Mean QALYs over 6 months was 0.379 in the OPCAB group and 0.362 in the CPB group , but the difference was not significant ( mean difference 0.017 ; SE 0.016 ; P = 0.305 ) . OPCAB surgery offered patients in this r and omized trial similar health benefits to CPB over a 6-month period , but at a significantly less cost The Beaver Dam Health Outcomes Study ( BDHOS ) is an ongoing longitudinal cohort study of health status and health-related quality of life for a r and om sample of adults ( age range at interview was 45 to 89 years ; mean = 64.1 , SD = 10.8 ) in a community population . In a face-to-face interview lasting approximately an hour , each participant responds to several batteries of questions . Included are a history of chronic medical conditions , current medi cations , and past surgeries ; the SF-36 ( a general health-status question naire ) ; the Quality of Well-being index ; self-rated health status on a five-point scale from " excellent " to " poor " ; and evaluation of current health using the method of time tradeoffs . The authors present results from 1,356 interviews on these four principal measures , reporting mean scores by sex , by age , and for persons reporting being affected by various medical conditions . They believe data from the BDHOS will provide research ers and policy makers a reference col lection of vital statistics for health-related quality of life . Additionally , the data provide a way to compare results from studies that utilize different indices from among the four principal measures of the BDHOS . Key words : health status ; quality of life ( health-related ) ; population study ; cohort study . ( Med Decis Making 1993;13:89 - 102 OBJECTIVES To assess the acceptability and feasibility of functional tests as a gateway to angiography for management of coronary artery disease ( CAD ) , the ability of diagnostic strategies to identify patients who should undergo revascularisation , patient outcomes in each diagnostic strategy , and the most cost-effective diagnostic strategy for patients with suspected or known CAD . DESIGN A rapid systematic review of economic evaluations of alternative diagnostic strategies for CAD was carried out . A pragmatic and generalisable r and omised controlled trial was undertaken to assess the use of the functional cardiac tests : angiography ( controls ) ; single photon emission computed tomography ( SPECT ) ; magnetic resonance imaging ( MRI ) ; stress echocardiography . SETTING The setting was Papworth Hospital NHS Foundation Trust , a tertiary cardiothoracic referral centre . PARTICIPANTS Patients with suspected or known CAD and an exercise test result that required non-urgent angiography . INTERVENTIONS Patients were r and omised to one of the four initial diagnostic tests . MAIN OUTCOME MEASURES Eighteen months post-r and omisation : exercise time ( modified Bruce protocol ) ; cost-effectiveness compared with angiography ( diagnosis , treatment and follow-up costs ) . The aim was to demonstrate equivalence in exercise time between those r and omised to functional tests and those r and omised to angiography [ defined as the confidence interval ( CI ) for mean difference from angiography within 1 minute ] . RESULTS The 898 patients were r and omised to  angiography  ( n = 222 ) , SPECT ( n = 224 ) , MRI ( n = 226 ) or stress echo ( n = 226 ) . Initial diagnostic tests were completed successfully with unequivocal results for 98 % of angiography , 94 % of SPECT ( p = 0.05 ) , 78 % of MRI ( p < 0.001 ) and 90 % of stress echocardiography patients ( p < 0.001 ) . Some 22 % of SPECT patients , 20 % of MRI patients and 25 % of stress echo patients were not subsequently referred for an angiogram . Positive functional tests were confirmed by positive angiography in 83 % of SPECT patients , 89 % of MRI patients and 84 % of stress echo patients . Negative functional tests were followed by positive angiograms in 31 % of SPECT patients , 52 % of MRI patients and 48 % of stress echo patients tested . The proportions that had coronary artery bypass graft surgery were 10 % ( angiography ) , 11 % ( MRI ) and 13 % ( SPECT and stress echo ) and percutaneous coronary intervention 25 % ( angiography ) , 18 % ( SPECT ) and 23 % ( MRI and stress echo ) . At 18 months , comparing SPECT and stress echo with angiography , a clinical ly significant difference in total exercise time can be ruled out . The MRI group had significantly shorter mean total exercise time of 35 seconds and the upper limit of the CI was 1.14 minutes less than in the angiography group , so a difference of at least 1 minute can not be ruled out . At 6 months post-treatment , SPECT and angiography had equivalent mean exercise time . Compared with angiography , the MRI and stress echo groups had significantly shorter mean total exercise time of 37 and 38 seconds , respectively , and the upper limit of both CIs was 1.16 minutes , so a difference of at least 1 minute can not be ruled out . The differences were mainly attributable to revascularised patients . There were significantly more non-fatal adverse events in the stress echo group , mostly admissions for chest pain , but no significant difference in the number of patients reporting events . Mean ( 95 % CI ) total additional costs over 18 months , compared with angiography , were 415 pounds ( -310 pounds to 1084 pounds ) for SPECT , 426 pounds ( -247 pounds to 1088 pounds ) for MRI and 821 pounds ( 10 pounds to 1715 pounds ) for stress echocardiography , with very little difference in quality -adjusted life-years ( QALYs ) amongst the groups ( less than 0.04 QALYs over 18 months ) . Cost-effectiveness was mainly influenced by test costs , clinicians ' willingness to trust negative functional tests and by a small number of patients who had a particularly difficult clinical course . CONCLUSIONS Between 20 and 25 % of patients can avoid invasive testing using functional testing as a gateway to angiography , without substantial effects on outcomes . The SPECT strategy was as useful as angiography in identifying patients who should undergo revascularisation and the additional cost was not significant , in fact it would be reduced further by restricting the rest test to patients who have a positive stress test . MRI had the largest number of test failures and , in this study , had the least practical use in screening patients with suspected CAD , although it had similar outcomes to stress echo and is still an evolving technology . Stress echo patients had a 10 % test failure 
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Similar findings were observed in estimates applying to general CHD .
No significant improvement in model fit was found after adjusting for study -level covariates .
Large between- study heterogeneity was observed in all the models investigated .
The main finding of our study is the presence of large heterogeneity both within and between instrument-specific HRQoL values .