Measuring the wole or the parts?

Interest has increased in recent years in incorporating health status measures into clinical practice for use at the individual-patient level. We propose six measurement standards for individual-patient applications: (1) practical features, (2) breadth of health measured, (3) depth of health measured, (4) precision for cross-sectional assessment, (5) precision for longitudinal monitoring and (6) validity. We evaluate five health status surveys (Functional Status Questionnaire, Dartmouth COOP Poster Charts, Nottingham Health Profile, Duke Health Profile, and SF-36 Health Survey) that have been proposed for use in clinical practice. We conducted an analytical literature review to evaluate the six measurement standards for individual-patient applications across the five surveys. The most problematic feature of the five surveys was their lack of precision for individual-patient applications. Across all scales, reliability standards for individual assessment and monitoring were not satisfied, and the 95% CIs were very wide. There was little evidence of the validity of the five surveys for screening, diagnosing, or monitoring individual patients. The health status surveys examined in this paper may not be suitable for monitoring the health and treatment status of individual patients. Clinical usefulness of existing measures might be demonstrated as clinical experience is broadened. At this time, however, it seems that new instruments, or adaptation of existing measures and scaling methods, are needed for individual-patient assessment and monitoring.

Patients confronted with a life-threatening or chronic disease are faced with the necessity to accommodate to their illness. An important mediator of this adaptation process is 'response shift' which involves changing internal standards, values and the conceptualization of quality of life (QOL). Integrating response shift into QOL research would allow a better understanding of how QOL is affected by changes in health status and would direct the development of reliable and valid measures for assessing changes in QOL. A theoretical model is proposed to clarify and predict changes in QOL as a result of the interaction of: (a) a catalyst, referring to changes in the respondent's health status; (b) antecedents, pertaining to stable or dispositional characteristics of the individual (e.g. personality); (c) mechanisms, encompassing behavioral, cognitive, or affective processes to accommodate the changes in health status (e.g. initiating social comparisons, reordering goals); and (d) response shift, defined as changes in the meaning of one's self-evaluation of QOL resulting from changes in internal standards, values, or conceptualization. A dynamic feedback loop aimed at maintaining or improving the perception of QOL is also postulated. This model is illustrated and the underlying assumptions are discussed. Future research directions are outlined that may further the investigation of response shift, by testing specific hypotheses and predictions about the QOL domains and the clinical and psychosocial conditions that would potentiate or prevent response shift effects.