Objective: To evaluate the sensitivity and utility of the Iowa Pain Thermometer (IPT) and other selected pain intensity scales in younger and older adults using a controlled clinical pain condition.
Design: A quasi-experimental study with 61 younger (age 21-55 years) and 36 older (age 65-87 years) adults experiencing arthritic pain at two rheumatology clinics. Before and after joint injection, patients reported current pain intensity with the following scales: IPT, Numeric Rating Scale (NRS), Verbal Numeric Rating Scale (VNS), Faces Pain Scale (FPS), and Visual Analog Scale (VAS).
Results: The IPT demonstrated the lowest failure rate of all pain intensity scales evaluated. Other scale failure rates were relatively low except for the VNS and the VAS. No significant difference was noted in scale failure by age, gender or education level, but cognitive impairment was significantly related to failure on the VAS and the NRS. All five pain scales were sensitive in detecting changes in pain intensity pre and post joint injection. All correlations between the scales were strong and significant; however, the intercorrelations for the older cohort were weaker. The scale most preferred in both cohorts of patients was the IPT, followed by the FPS.
Conclusions: Based on sensitivity to change, lower failure rates, higher preference evaluations, and little appreciable affects associated with cognitive impairment, the IPT was judged to be the best choice for assessing pain intensity for both age cohorts and warrants further study.