An investigation of the use of a numeric pain rating scale with ice application to the neck to determine cold hyperalgesia

Abstract

The presence of cold hyperalgesia is a predictor of poor health outcomes following whiplash injury. An appropriate clinical test to identify cold hyperalgesia may help in gauging the prognosis. A repeated measures, within subjects design was used. Sixty-three participants with chronic Whiplash Associated Disorder (WAD) (grade II and III) underwent testing at the cervical spine for sites of cold hyperalgesia with laboratory testing equipment, as well as a test of reported pain intensity on an 11 step numerical rating scale (NRS) after 10 s of ice application at the same sites. A receiver operating characteristic analysis was used to evaluate the ability of the ice application test to discriminate between cold hyperalgesic and non-cold hyperalgesic sites, as determined by the laboratory equipment. Pain sensation on ice application was significantly better than chance in discriminating between cold hyperalgesic and non-cold hyperalgesic sites (AUC 0.822 (95% CI 0.742-0.886); p < 0.0001). Sensitivities, specificities and likelihood ratios for different NRS values for pain intensity are presented. A pain intensity rating of >5 gave a positive likelihood ratio of 8.44 suggesting that if this value is reported, clinicians could be suspicious of the presence of cold hyperalgesia. This study demonstrates simple clinical test that may aid in gauging prognosis and guiding treatment decisions in people with WAD.