The measurement of pain.

Pain has been studied in depth for decades, yet the pain associated with cancer is still frequently under treated. The measurement of pain in patients with terminal cancer is imperative, because failure to carry it out is recognised as an important reason for inadequate treatment. Although pain is characterised as a symptom, it is a subjective personal experience or a perception. This perception is influenced by both nociceptive transmission and central nervous system modulation; and psychological, social and other environmental factors. It is a complex issue most simply described by the phrase 'Pain is whatever the experiencing person says it is, existing whenever he says it does'. With such complex interplays between pathophysiological and biopsychosocial factors, it is unsurprising that an objective assessment of pain remains elusive. Despite this, many subjective measures of pain have been developed that produce consistent and reliable results when used properly and appropriately.