Joannie Shen; Michael Johnston; Ron D Hays

Disclosures

Expert Rev Pharmacoeconomics Outcomes Res. 2011;11(4):447-453. 

In This Article

Health-related Quality of Life

The National Asthma Education and Prevention Program recommends using patient-reported outcomes such as HRQOL measures to assess asthma control. HRQOL includes physical functioning, role limitations, emotional wellbeing, social functioning and a variety of symptoms such as pain and energy or fatigue levels, along with disease-targeted symptoms.[17] HRQOL measures provide an important indication of the effects of asthma on daily functioning and wellbeing.[18] Generic HRQOL instruments such as the Short Form (SF)-36 provide a means to compare the effects of asthma with those of other conditions such as cancer.[19]

Role functioning and work-related productivity are among the most important aspects of HRQOL for asthma. Health-related work productivity losses may occur through either absenteeism (time missed from the workplace) or presenteeism (reduced productivity while at the workplace).[20] Mattke et al. conducted a systematic review of methods to measure and monetize health-related work productivity loss.[21] Support for the reliability and validity of several of these methods has been published.[22,23] The Work Limitations Questionnaire[24] and the nonproprietary WHO Health and Work Performance Questionnaire[25,26] are perhaps the two most highly regarded measures of health-related work productivity loss.[27] However, the survey instrument most often used in research is the nonproprietary Work Productivity Assessment Instrument.[28] Using these tools to measure health-related work productivity losses provides information on the ways in which asthma impacts on the ability of adults to work and participate fully when at work.

Asthma-targeted instruments such as the Asthma Quality of Life Questionnaire[15] and Asthma Quality of Life Questionnaire (Marks')[29,30] provide in-depth information about the effects of asthma on functioning and wellbeing. Meads et al. developed the Asthma Life Impact Scale to go beyond the earlier focus on symptoms, functioning and environmental triggers.[31] For example, the Asthma Life Impact Scale includes items to assess emotional issues not represented in other instruments. Turner-Bowker et al. developed an online computerized adapting test (ASTHMA-CAT) that assesses HRQOL with minimal respondent burden.[32]

Preference-based measures integrate across domains to produce a single summary score for each health state anchored relative to 'dead' (score of 0) and 'perfect' or 'full' health (score of 1). Some of the most widely used preference-based measures include the Quality of Wellbeing scale,[33] the Health Utilities Indexes Mark 2 and Mark 3,[34] the EuroQol-5D[35] and the SF-6D.[36] However, these measures are not interchangeable. For example, Kaplan et al. administered the five preference-based measures to a sample of 457 cataract patients before and after surgery and found statistically significant improvements in HRQOL 1 month after surgery for all indexes except the SF-6D.[37] The mean differences in HRQOL ranged from 0.00 (for the SF-6D) to 0.06 (for the Health Utilities Indexes Mark 3).

Preference-based measures are especially important for cost–effectiveness analyses used to evaluate different interventions. Quality-adjusted life years (QALYs) combine preference-based measures and life expectancy to yield a single measure of the morbidity and mortality effects. QALYs were recommended by the Institute of Medicine's Committee to Evaluate Measures of Health Benefits for Environmental, Health and Safety regulation.[38] Two alternatives similar to QALYs for measuring disease burden are healthy-year equivalents and disability-adjusted life years. Healthy-year equivalents measure the number of years in optimal health that yield the same level of utility as a particular lifetime health profile that reflects all health states experienced over one's lifetime. Disability-adjusted life years represent the number of healthy years of life lost owing to death or disability and are estimated by assigning disability scores to diseases.

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