Measurement of
pain in
cancer patients requires all the procedural safeguards essential for the measurement of subjective responses, including the employment of active and inactive controls, double-blind techniques, randomization, and statistical verification of results.
Pain is traditionally measured in
analgesic studies by employing verbal descriptors of intensity, but more recently visual analogues of
pain intensity have been used and generally provide more sensitive measures of
pain intensity. Patients with
chronic pain tend to rate the categories representing more intense
pain as lower in the visual analogue scale than do patients with
postoperative pain. This may well reflect differences in the prior
pain experiences of the two groups. Patients with chronic
cancer pain have greater positive mood effects after the
narcotic,
morphine, than after the non-steroidal antiinflammatory
analgesic,
zomepirac, and this appears to be independent of
analgesic activity. It is possible to design crossover
analgesic studies in
cancer patients so as to minimize carry-over effects, and such studies are more efficient than parallel group assays. Crossover studies also provide the ability to measure carry-over when it occurs.