ABSTRACT
Pain is a personal experience, and consequently is difficult to define. It includes both the sensory input and any modulation by physiological, psychological and environmental factors. Not surprisingly, there are no objective measures – there is no way to measure pain directly by sampling blood or urine or by performing neurophysiological tests. Measurement of pain must therefore rely on recording the patient’s report. The assumption is often made that because the measurement is subjective it must be of little value. The reality is that if the measurements are made properly, then remarkably sensitive and consistent results can be obtained. There are contexts, however, when it is not possible to measure pain at all, or when reports are likely to be unreliable. These include impaired consciousness, young children, psychiatric pathology, severe anxiety, unwillingness to cooperate, and inability to understand the measurements. Such problems are deliberately avoided in trials, but are all too common in the clinical setting.
