Do medical house officers value the health of veterans differently from the health of non-veterans? Patient utilities in chronic musculoskeletal pain: how useful is the standard gamble method? Quality of life in epilepsy: comparison of four preference measures Proportional Heuristics in Time Tradeoff and Conjoint Measurement
Background Little information is available regarding medical residents ' perceptions of patients ' health-related quality of life . Patients cared for by residents have been shown to receive differing patterns of care at Veterans Affairs facilities than at community or university setting s. We therefore examined : 1 ) how resident physicians value the health of patients ; 2 ) whether values differ if the patient is described as a veteran ; and 3 ) whether residency-associated variables impact values . Methods All medicine residents in a teaching hospital were asked to watch a digital video of an actor depicting a 72-year-old patient with mild-moderate congestive heart failure . Residents were r and omized to 2 groups : in one group , the patient was described as a veteran of the Korean War , and in the other , he was referred to only as a male . The respondents assessed the patient 's health state using 4 measures : rating scale ( RS ) , time tradeoff ( TTO ) , st and ard gamble ( SG ) , and willingness to pay ( WTP ) . We also ascertained residents ' demographics , risk attitudes , residency program type , post-graduate year level , current rotation , experience in a Veterans Affairs hospital , and how many days it had been since they were last on call . We performed univariate and multivariable analyses using the RS , TTO , SG and WTP as dependent variables . Results Eighty-one residents ( 89.0 % of eligible ) participated , with 36 ( 44.4 % ) viewing the video of the veteran and 45 ( 55.6 % ) viewing the video of the non-veteran . Their mean ( SD ) age was 28.7 ( 3.1 ) years ; 51.3 % were female ; and 67.5 % were white . There were no differences in residents ' characteristics or in RS , TTO , SG and WTP scores between the veteran and non-veteran groups . The mean RS score was 0.60 ( 0.14 ) ; the mean TTO score was 0.80 ( 0.20 ) ; the mean SG score was 0.91 ( 0.10 ) ; and the median ( 25th , 75th percentile ) WTP was $ 10,000 ( $ 7600 , $ 20,000 ) per year . In multivariable analyses , being a resident in the categorical program was associated with assigning higher RS scores , but no residency-associated variables were associated with the TTO , SG or WTP scores . Conclusion Physicians in training appear not to be biased either in favor of or against military veterans when judging the value of a patient 's health The main goal of current pain management approaches is to increase the patients ' quality of life by improving pain coping skills and by reducing the levels of disability in daily life , often despite persistent pain . Direct measurement of quality of life is of crucial importance in economic evaluation research , in which not only is the estimation of financial costs and benefits included , but so is the evaluation of costs and benefits in terms of changes in health states . The purpose of this study is to compare the psychometric qualities of two instruments for assessing patients ' utilities , the  rating scale ( RS )  and the st and ard gamble ( SG ) . Such instruments are design ed for their application in economic evaluation research , but have seldomly been used in chronic pain trials . Both methods provide a single measure between 0 and 1 . The relationship between these utility measures and descriptive and domain-specific quality of life measures was examined in 133 fibromyalgia patients and 148 patients with chronic non-specific low back pain .  Mean utility score at baseline was 0.43 with the RS and 0.78 for the SG . The correlation between both methods was found to be poor ( r = 0.21 ) . Both measures appeared to be fairly stable in a 2-week test-retest period ( intra class correlation coefficient ( ICC ) = 0.74 and 0.77 ) . Scores on the description of patient 's own health on six domains , global assessment of change and domain specific measures correlated moderately with the RS scores and low with the SG . Multiple regression analyses demonstrated that 32 % of the variance in RS values and only 13 % of the variance in SG utilities could be explained by domain-specific measures . These results suggest an acceptable construct validity for the RS but insufficient construct validity for the SG . Valuations of ones own health appear only partially to be related to the assessment of the pain-specific measures and measures of distress . It can be concluded that the RS and domain-specific measures assess partly different , but nevertheless complementary aspects of health-related quality of life . It is therefore recommended to include in economic evaluation studies both domain-specific measures and valuation measures . Finally , in chronic musculoskeletal pain patients , RS scores were found to be more responsive in detecting significant changes in preferences than SG scores . For use in patients with chronic musculoskeletal pain , the RS is preferred to the SG for establishing accurate decisions about the impact of new interventions on their health outcomes Several specific and general measures are available for the assessment of overall health related quality of life in epilepsy . Few of the commonly used measures provide utility weights for use in cost-utility analyses . This study compares four methods for measuring utility weights : time trade-off ( TTO ) , st and ard gamble ( SG ) , 15D , end the EuroQol visual analog scale .  All patients aged 18 - 67 years with a diagnosis of epilepsy , who had been admitted to or attended the outpatient clinic at a large county hospital 1987 - 1994 , received a comprehensive question naire . From 397 respondents , 82 patients were r and omly selected . Most of the 57 patients completing the study generally had well-controlled epilepsy , but were still on anti-epileptic medication . Mean age was 44 years . Fourty-one percent were male and 59 % female . The result ing utility weights differed considerably between the measures , both with regard to central tendency and dispersion . Median utility scores : EuroQol visual analog scale 0.75 , 15D 0.90 , TTO 0.98 , SG 0.99 . There was a good association between the EuroQol rating scale and the 15D , and a moderate association between SG and TTO . These preference instruments measure different aspects of health-related quality of life and thus yield different results . Caution should be taken when interpreting cost-utility studies , as results will depend on the choice of utility instrument The time-tradeoff ( TTO ) test is widely used to measure quality of life for different health states . Subjects are asked to equate the value of living a given period in an inferior health state to the value of living a shorter period in good health . Applications of TTOs have been criticized based on the fact that the value of future life duration is taken as the future life duration itself . The authors show that for a health state in which a subject does not want to live longer than a specified amount of time , subjects ' responses do not comply with the assumption that the value of the period in inferior health is equated to the value of the shorter period in good health Actually , preference reversals with respect to such a health state point to the use of a proportional heuristic in the TTO test . Comparisons of the TTO test in these subjects with category scaling and difference measurements also favor a proportional inter pretation of the TTO test . In tests based on conjoint measurement , these subjects also appear to use a proportional heuristic . Consequences of the use of the TTO test and conjoint measurement m quality -of-life models are discussed Key words : utility assessment , QALY , conjoint measurement ; preference reversals ; compatibility effect . ( Med Decis Making 1996;16:36 - 44
The results of this study do not support the common view that RS values are lower than TTO values , may suggest that TTO biases largely cancel , and support the validity of formulas for correcting SG bias
Background .
A common assertion is that rating scale ( RS ) values are lower than both st and ard gamble ( SG ) and time tradeoff ( TTO ) values .
However , differences among these methods may be due to method specific bias .
Although SG and TTOs suffer systematic bias , RS responses are known to depend on the range and frequency of other health states being evaluated .
Over many diverse studies this effect is predicted to diminish .
Thus , a systematic review and data synthesis of RS-TTO and RS-SG difference scores may better reveal persistent dissimilarities .
The purpose of this study was to establish through systematic review and meta- analysis the net effect of biases that endure over many studies of utilities .