Cancer pain intensity measurement: concurrent validity of three tools--finger dynamometer, pain intensity number scale, visual analogue scale

Abstract

Although the visual analogue scale (VAS) and number scales are known to be valid and sensitive measures of pain intensity, some older individuals are unable to use them. For individuals who lack the ability to use these scales, valid alternative measures of pain intensity would be useful for research and clinical practice. The purpose of this study was to examine the concurrent validity of a new measure of pain intensity, the Finger Dynamometer (FD), in a sample of 15 adults with advanced stage cancer pain. In a repeated measures correlational design each patient rated present pain intensity using the FD, a Pain Intensity Number Scale (PINS), and a VAS at four separate times. Data analyses using Kendall Correlational Coefficients indicated weak to moderate correlation between the FD and PINS (gamma = .47 to .68; p less than .01) and between the FD and VAS (gamma = .38 to .46; p less than .05) at each measurement time. Strong correlation was found between the VAS and the PINS (gamma = .77 to .89; p less than .001). Findings support the concurrent validity of the VAS and the PINS but indicate that further research is necessary to establish the psychometric properties of the FD as a measure of pain intensity in chronic pain models, such as cancer pain. Recommendations are made regarding important variables to be considered in further research with the FD.