Measuring patient-reported outcomes: moving beyond misplaced common sense to hard science

Abstract

Interest in the patient's views of his or her illness and treatment has increased dramatically. However, our ability to appropriately measure such issues lags far behind the level of interest and need. Too often such measurement is considered to be a simple and trivial activity that merely requires the application of common sense. However, good quality measurement of patient-reported outcomes is a complex activity requiring considerable expertise and experience. This review considers the most important issues related to such measurement in the context of chronic disease and details how instruments should be developed, validated and adapted for use in additional languages. While there is often consensus on how best to undertake these activities, there is generally little evidence to support such accord. The present article questions these orthodox views and suggests alternative approaches that have been shown to be effective.

Figure 1

Key considerations for patient-reported outcome questionnaire development. The major factors that should be considered when selecting a patient-reported outcome measurement (PROM) for use in clinical studies are shown. These emphasise the importance of ensuring that the PROM addresses the required outcome, that it has been carefully developed and that all versions developed (including language adaptations) are of good quality.

Figure 2

Employment-related needs. The relationships between function, objective and needs satisfaction are shown. Here employment is a function undertaken to obtain income. However, undertaking the function leads to the satisfaction of a range of needs (some of which are listed). Quality of life (QoL) is the result of satisfaction of the needs rather than earning an income per se.

Figure 3

Types of PROMs currently used in medical research. The range of different types of patient-reported outcomes (PROs) is shown. The most commonly used PROMs assess symptoms and/or functional limitations. These are commonly referred to as health-related quality of life (HRQL) measures. The commonly used measures which generate utility values also ask about symptoms and/or functional limitations. Patient satisfaction is generally concerned with issues such as the process of treatment and relationships with clinical staff. QoL measures address need-fulfilment rather than symptoms and/or functional limitations.

Figure 4

Brief checklist for assessing the quality of PRO instruments. The specific requirements of a good-quality PROM are shown. These qualities should be clearly reported in peer-reviewed publications. In many cases (including that of the most commonly employed PROMs), this information is not available. New instrument development methodologies, in particular the establishment of the scaling properties of a measure (item response theory), are essential to ensuring the quality of PROMs.