Keynotes

KEYNOTE 3
Overview of Health Status and
Health Related Quality of Life Measures

Ellen J. MacKenzie, Ph.D.

Introduction

Over the past two decades significant advances have been made in the development of methods for assessing health status and health related quality of life (HRQOL) (McDowell and Newell, 1996; Ware, 1995; McHorney, 1999; Varni et al, 1999). Much of this developmental work has focused on: (1) defining the dimensions of health; (2) developing an array of generic and disease specific instruments; and (3) demonstrating their reliability and validity for a variety of applications including both evaluative and policy research. Only recently, however, have we seen these measures applied in assessing injury outcome. Very few studies have been published in which HRQOL measures have been used in the evaluation of specific interventions or policies. As the injury field increasingly focuses its attention on the prevention and treatment of non-fatal injuries and their consequences, the broader use of these measures becomes imperative. Just as we have developed standardized approaches for counting and classifying injuries, so too must we develop and broadly apply methods for monitoring their impact on the individual and society.

What are Health Status and Health Related Quality of Life Measures?

Today we will be reviewing several consumer-oriented measures of health status and HRQOL that are relevant to the study of injury outcomes. These measures generally include both objective and subjective components of human functioning and well-being, measure health from the consumer’s point of view (as opposed to that of a health care provider) and tap into multiple domains of health that are relevant to the individual and society. The emphasis on these measures as opposed to clinical measures of morbidity and impairment reflects the growing recognition that the consumer’s perspective of his or her health and well-being is central to the development and evaluation of cost-effective programs and policy (Relman, 1988; Gold et al., 1996). Domains usually included in a general health status or HRQOL scale are: physical health and self-maintenance; cognitive function; mental health; social function; role function and general health perceptions. Health status measures typically combine assessments of both activity restrictions (i.e., difficulty in the integrated use of body functions in the performance of a specific task or action) and participation restrictions (i.e., problems in the manner or extent of involvement in life situations-in the context of a person’s actual environment) into one measure or profile (World Health Organization, 1997).

A plethora of health status measures have been proposed in the literature (McDowell and Newell, 1996; Ware in Annu Rev Public Health, 1995; McHorney 1999; Varni et al., 1999). The choice of measure for any particular application will clearly depend on several factors, including: (1) the appropriateness of the measure’s content to the research question or application; (2) the evidence of its reliability, validity and responsiveness to changes over time and differences in treatment; (3) level of aggregation provided by the measure; (4) availability of population norms; and (4) practical considerations (e.g., mode of administration, time needed to administer, respondent burden, availability of documentation and supporting materials). Some measures are generic, developed for application across different populations and conditions, while others are disease or condition specific. Although controversy still exists regarding the benefits of generic versus condition specific measures, current wisdom suggests that where at all possible, the use of both a brief generic measure, supplemented by a condition specific measure targeted at the issue under investigation is often advantageous (Patrick and Deyo, 1989; Guyatt et al., 1996). When using these measures for documenting and monitoring the burden of injury, there is considerable appeal in using a generic measure as it facilitates comparisons with other leading causes of death and disability. In addition, generic measures may be particularly useful in measuring consequences of multiple trauma where multiple body systems are affected, with consequences that affect multiple aspects of function.

Health status and HRQOL measures are generally characterized as either (1) psychometric measures or health status profiles; or (2) preference based or utility based measures (Ware et al., in Annu Rev Public Health, 1995). A psychometric measure describes the health profile of an individual across multiple domains of function and typically provides a score for each domain as well as one or more summary scores that combine assessments across domains, yielding overall measures of physical and mental health. A preference-based measure, on the other hand, provides only a single overall score and combines both death and quality of life into a single metric. These measures typically range from 0 (representing death) to 1 (optimal health). They reflect the explicit preferences of patients or consumers for different profiles of health status. These preferences are derived using decision theory and economic principles (Bennett and Torrance, 1996). Because they combine death and quality of life into one number, they can be used together with survival data in deriving quality adjusted life years (QALYs). The QALYs, in turn, can be used in the analysis of the tradeoffs between costs and effectiveness. Preference-based measures are less useful, however, for understanding the specific dimensions of injury outcomes and are of limited value in examining the impact of particular treatments over time.

Commonly Used Measures for Measuring 
the Health of Adults and Children

Examples of psychometric measures and preference-based measures are listed in Table 1, together with a number of peer-reviewed articles identified in which each scale was used to examine outcomes following acute traumatic injury. These articles were identified by first searching The National Library of Medicine’s “PubMed Database” for all articles that referred to the instrument either directly in the text or indirectly through references. The search was then restricted to those articles in which injury or trauma were listed as a MESH heading. Finally, a review of the abstracts was performed to eliminate articles that did not specifically report on the use of the instrument in an injury or trauma population. The most widely used instruments for measuring the impact of injury include the Barthel Index of Activities of Daily Living; the Functional Independence Measure (FIM); the Sickness Impact Profile (SIP); and the Short Form Health Survey or SF-36. An additional four articles were identified that used the Quality of Well-being Scale (QWB) and the European Quality of Life Scale (EuroQoL). All of these measures were discussed at length during the conference. To illustrate the utility of a brief, generic measure of health status, the SF-36 and its application in an injury population is described here in more detail.

The SF-36 was designed as a generic indicator of health status for use in large population-based studies (Ware and Sherbourne, 1992; McHorney et al., 1993). It was derived from a set of more detailed measures developed for use in the Medical Outcomes Study and consists of 35 items or questions that are scaled to measure eight general health concepts: physical functioning; role limitations due to physical health problems; bodily pain; general health perceptions; vitality; social functioning; role limitations due to emotional problems; and general mental health (Ware and Sherbourne, 1992). An additional question asks respondents to describe changes in health status during a one-year period but is not used to score any of the eight scales. Two summary scores can be derived that measure physical and mental health respectively (Ware et al., in Med Care, 1995). The SF-36 may be self-administered or administered by an interviewer and takes only 5 to 10 minutes to complete. Because it is relatively short in length, it can be readily incorporated as part of a telephone interview. A British-English version of the SF-36 has been developed (Brazier et al., 1993) and the instrument has also been adapted for use in several other languages (Ware et al., 1998). Norms for the general U.S. and British populations (by specific age and gender groups) are available, as are norms for persons with varying medical conditions (Ware et al., 1993). The SF-36 was developed with exquisite attention paid to issues of reliability and validity (Ware et al., 1996). As will be true with any abbreviated measure, however, the SF-36 is somewhat more limited in scope when compared to more detailed instruments such as the Sickness Impact Profile. The use of the SF-36 in outcomes research is now widespread across a variety of conditions and populations (Ware et al., 1998). However, few published examples of its application to injury are available (McCarthy et al., 1995; Kopjar, 1996; Beaton et al., 1994; Corrigan et al., 1998; MacKenzie and McCarthy, in press).

With regard to the application of the SF-36 in trauma outcomes research, the lack of items specifically relating to cognitive function is of some concern. The SF-36 was applied to a sample of individuals who had been hospitalized a year earlier at one of 12 trauma centers in the state of Pennsylvania (MacKenzie and McCarthy, in press). The sample was constructed to over-represent the more severe injuries (50% had Injury Severity Scores (ISS) of 16 or greater; average length of stay was 12 days). Scores in all dimensions except vitality and mental health were significantly worse than general population norms appropriate to the age and gender distribution of the study population. When patients with and without orthopedic injury were compared, significant differences in SF-36 scores were also observed. However, when profiles were compared for patients with and without varying levels of traumatic brain injury (TBI), adjusting for the level of orthopedic injury, we found few consistent differences. To address this limitation of the SF-36 we supplemented the SF-36 with three items asking about limitations in attention span, problem solving, and memory. By summing responses to each item a cognitive function scale was derived. This score was shown to be internally consistent and measured a component of health that appeared to be independent of the dimensions incorporated in the SF-36. It also correlated reasonably well with established measures of brain injury severity. Although further studies are needed to validate the specific items chosen for measuring cognitive function, the results of this study underscored the need to supplement the SF-36 with such a measure when evaluating outcomes from multiple traumas involving head injury.

A study by McCarthy, Copeland and colleagues on outcome following pelvic fractures among young women further illustrates how the SF-36 can be used in examining outcomes post-injury but also points to the limitations of using generic measures when focusing on specific types of injury and injury consequences (McCarthy et al., 1995; Copeland et al., 1997). A group of 123 women with pelvic ring fractures were retrospectively identified and compared to a similar group of 110 women who sustained a lower extremity fracture (matched by age, year of injury and injury severity). A telephone interview was administered two to eight years post injury to assess functional outcome. Compared to age and gender adjusted population norms, both groups of women scored significantly worse (lower scores) on all dimensions of the SF-36 except mental health. There was no significant difference between the fracture groups, however; suggesting that outcomes from major pelvic fractures were no worse than those associated with significant lower extremity fractures.

Of particular interest in examining outcomes from pelvic fracture, however, was the impact of the injury on genitourinary and sexual function. Although several studies had described impotence among male pelvic fracture patients, the effect of pelvic trauma on the sexually active female had not been documented. The SF-36 does not include items related to either of these problem areas. For this reason, the SF-36 was supplemented with questions related to urinary and bowel complaints as well as sexual function (including the presence and location of dyspareunia). Results showed that after adjusting for demographics and co-morbidities, women with moderate to severe pelvic fracture were significantly more likely than women with mild pelvic fractures or extremity fractures to have urinary problems and gynecologic pain during sexual activity (Copeland et al., 1997). As might be expected, however, women with pelvic fractures (any severity) as well as those with moderate to severe extremity fractures were more likely than women with minor extremity fractures to report musculo-skeletal pain during sexual activity. This study served to heighten the awareness of orthopedists to issues of genitourinary and sexual function following both pelvic and major extremity trauma.

Challenges and Recommendations

As we proceed in reviewing the many instruments that have been proposed for measuring health status and health related quality of life, we must be mindful of the challenges involved in their application. Some of these challenges cut across all conditions, while others are specific to measuring the consequences of injury. Already mentioned above is the need for measures that are sensitive to decrements in function across multiple body systems. Comprehensive measures, however, tend to be long and impractical for many applications, especially those involving population based research and evaluation. The SIP, for instance, taps into multiple domains, each with considerable depth; however, it takes 20 minutes to administer. The SF-36 takes only 5-10 minutes to administer but is not sensitive to decrements in cognitive function following brain injury. Measuring outcome from head injury, in general, poses significant challenges. For the individual with a more severe head injury, we are faced with the decision regarding the use and interpretation of proxy respondents. Another challenge specific to any study of the impact of injury is the lack of “before” measures, making the interpretation of post-injury assessments difficult, especially among the elderly, who are more likely to have pre-injury limitations.

Perhaps the biggest challenge, however, involves the determination of factors that influence outcome post-injury. Just as we have developed a better understanding of the epidemiology of injury and the risk factors associated with the occurrence of injurious events, so too must we develop an understanding of the factors that influence the consequences of injury once it occurs. While several studies have examined the impact of injury severity, age and pre-existing conditions on outcome, few have taken a broader perspective and identified the characteristics of the individual and his environment that are important in determining recovery and the risks of poor outcome. Several conceptual frameworks of health and health status have been proffered in the literature that is useful in examining the epidemiology of outcomes (Wilson and Cleary, 1995; Nagi, 1976; Institute of Medicine, 1997; WHO, 1997). It will be important for those in the field to begin applying these frameworks to better define the consequences of injury and elucidate the causal patterns associated with good and poor outcome.

References

• Beaton DE, Bombardier C, Hogg-Johnson S. Choose your tool: a comparison of the psychometric properties of five generic health status instruments in workers with soft tissue injuries. Qual Life Res. 1994;3:50-56. 
• Bennett KJ, Torrance GW. Measuring health state preferences and utilities: rating scale, time trade-off, and standard gamble techniques. In: Spilker B, ed. Quality of Life and Pharmacoeconomics in Clinical Trials. Philadelphia, PA: Lippincott-Raven Publishers; 1996. 
• Bergner M, Bobbitt RA, Carter WB, et al. The SIP: Development and final revision of a health status measure. Med Care. 1981;19:787. 
• Brazier J, Jones N, Kind P. Testing the validity of the EuroQol and comparing it with the SF-36 Health Survey Questionnaire. Qual Life Res. 1993;2:169-180 
• Brenneman FD, Katyal D, Boulanger BR, et al. Long-term outcomes in open pelvic fractures. J Trauma. 1997;42:773-777. 
• Copeland CE, Bosse MJ, McCarthy ML, et al. Effect of trauma and pelvic fracture on female genitourinary, sexual, and reproductive function. J Orthop Trauma. 1997;11:73-81. 
• Corrigan JD, Smith-Knapp K, Granger CV. Outcomes in the first 5 years after traumatic brain injury. Arch Phys Med Rehabil. 1998;79:298-305. 
• DeBruin AF, De Witte LP, Stevens F, et al. Sickness Impact Profile: the state of the art of a generic functional status measure. Soc Sci Med. 1992;35:1003-1014. 
• Elvik R. The validity of using health state indexes in measuring the consequences of traffic injury for public health. Soc Sci Med. 1995;40:1385-1398. 
• EuroQol Group. EuroQol: a new facility for the measurement of health-related quality of life. Health Policy. 1990;16:199-208. 
• Feeny D, Furlong W, Boyle M, Torrance GW/ Multi-attribute health status classification systems: the Health Utilities Index. PharmacoEconomics. 1995;7:490-502. 
• Gold MR, Siegel JE, Russell LB, Weinstein MC, eds. Cost-Effectiveness in Health and Medicine. New York: Oxford University Press; 1996. 
• Granger CV, Hamilton, BB, Linacre JM, et al. Performance profiles of the Functional Independence Measure. Am J Phys Med Rehabil. 1993;72:84-89. 
• Guyatt GH, Jaeschke R, Feeny DH, Patrick DL. Measurements in clinical trials: choosing the right approach. In: Spilker B, ed. Quality of life and Pharmacoeconomics in Clinical Trial. Philadelphia, PA: Lippincott-Raven Publishers; 1996. 
• Institute of Medicine. Brandt EN, Pope AN, eds. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: National Academy Press; 1997. 
• Kaplan RM, Bush JW. Health-related quality of life measurement for evaluation research and policy analysis. Health Psychol. 1982;1:61-80. 
• Kopjar B. The SF-36 Health Survey: A valid measure of changes in health status after injury. Injury Prev. 1996;2: 135-139. 
• Landgraf JM, Abetz LN, Ware JE. The CHQ User’s Manual. Boston, MA: The Health Institute, New England Medical Center; 1996. 
• Landgraf JM, Abetz LN. Measuring health outcomes in pediatric populations: issues in psychometrics and application. In: Spilker B, ed. Quality of Life and Pharmacoeconomics in Clinical Trials. Philadelphia, PA: Lippincott-Raven Publishers; 1996. 
• Linacre JM, Heinemann AW, Wright BD, et al. The structure and stability of the Functional Independence Measure. Arch Phys Med Rehabil. 1994;75:127-132. 
• MacKenzie EJ, Dainiano A, Miller T, Luchter S. The development of the Functional Capacity Index. J Trauma. 1996;41: 799-807. 
• MacKenzie EJ, McCarthy M. Validating the SF-36 for measuring outcome following multiple trauma. Manuscript in Press 2000. 
• Mahoney Fl, Barthel DW. Functional evaluation: The Barthel Index. Md Med J. 1965;14:61-65.
• McCarthy ML, MacKenzie EJ, Bosse MJ, et al. Functional status following orthopedic trauma in young women. J Trauma. 1995;39:828-837. 
• McDowell I, Newell C. Measuring Health. New York, NY: Oxford University Press; 1996. 
• McHorney CA, Ware JE Jr, Raczek AE. The MOS 36-item Short Form Health Survey (SF-36): II. Psychometric and clinical tests of validity in measuring physical and mental health constructs. Med Care. 1993;31:247-263. 
• McHorney CA. Health Status assessment method for adults: Past accomplishments and future challenges. Annu Rev Public Health. 1999;20:309-35. 
• Nagi S. An epidemiology of disability among adults in the United States. Milbank Q. 1976;54:439-468. 
• Patrick DL, Deyo. Generic and disease specific measures in assessing health status and quality of life. Med Care. 1989;27:S217-S232. 
• Relman AS. Assessment and accountability: The third revolution in health care. N Engl J Med. 1988;319:1220-1222. 
• Starfield B, Reiley A, Green B, et al. The adolescent child health and illness profile: a population-based measure of health. Med Care. 1997;33:553-566. 
• Stein REK and Jessop DJ. Functional status II(R): a measure of child health status. Med Care. 1990;28:1041-1055. 
• Stewart AL, Greenfield S, Hays RD, et al. Functional status and well-being of patients with chronic conditions. JAMA. 1989;262:907-913. 
• Varni JW, Seid M, Kurtin PS. Pediatric health-related quality of life measurement: a guide for health care decision makers. JCOM. 1999:6:33-40. 
• Varni JW, Seid M, Rode CA. The PedsQL: measurement model of the pediatric quality of life inventory. Med Care. 1999;37:126-139. 
• Ware JE, Sherbourne CD. The MOS 36-item Short-Form Health Survey (SF-36). I. Conceptual framework and item selection. Med Care. 1992;30:473-483. 
• Ware JE Jr, Snow KK, Kosinki M, et al. SF-36 Health Survey: Manual and Interpretation Guide. Boston, MA: The Health Institute, New England Medical Center; 1993. 
• Ware JE , Kosinski M, Keller SD. SF-36 Physical and Mental Health Summary Scores: a User’s Manual. Boston, MA: The Health Institute, New England Medical Center; 1994. 
• Ware JE. The status of health assessment in 1994. Annu Rev Public Health. 1995;16:327-354. 
• Ware JE, Kosinski M, Bayliss MS, et al. Comparisons of methods for the scoring and statistical analysis of the SF-36 health profile and summary measures: Summary of results from the Medical Outcomes Study. Med Care. 1995;33:AS264-AS279. 
• Ware JE , Kosinski M, Keller SD. A 12 item Short Form Health Survey: Construction of scales and preliminary tests of reliability and validity. Med Care. 1996;3:220-233. 
• Ware JE, Gandek B, Kosinski M, et al. The equivalence of SF-36 summary health scores estimated using standard and country-specific algorithms in 10 countries: results from the International Quality of Life Assessment Project. J Clin Epidemiol. 1998;51:1167-1170. 
• Wilson IB, Cleary PD. Linking clinical variables with health related quality of life: A conceptual model of patient outcomes. JAMA. 1995;273:59-65. 
• World Health Organization. The International Classification of Impairments, Activities and Participation. A Manual of Dimensions of Disablement and Functioning. Beta-1 Draft for Field Trials. Geneva Switzerland: World Health Organization; 1997.

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