Pain measurement is a critical issue, because it serves as the primary basis for determining pain-related diagnoses and treatment efficacy. However, pain is by definition an internal and personal phenomenon; therefore, clinicians and scientists must infer a patient's pain experience entirely from indirect measures. This chapter will discuss the multiple methods of pain assessment that are available, including consideration of the circumstances under which each method may be most useful. Before reviewing specific methods, a brief overview of important issues in pain measurement will be provided.

Issues in pain measurement

Pain assessment must accommodate the complexity and multidimensionality of the pain experience. For example, the International Association for the Study of Pain's definition of pain states ‘pain is an unpleasant sensory and emotional experience….’ Optimal pain assessment should include measurement of both the sensory and emotional dimensions of pain. Unfortunately, the most commonly used pain scales represent one-dimensional measures of pain severity (e.g. a single 0–10 pain rating), which fail to separate affective and sensory components. In addition, pain involves not only a perceptual experience, but also behavioural, physiological and psychological responses (e.g. see Table 10.1). Therefore, the assessment of pain must extend beyond the perceptual experience to incorporate responses from these different domains.