The presence of cold hyperalgesia may be an important prognostic indicator for persistent pain. However, a simple and inexpensive clinical testing method is needed. This report summarizes a series of studies in healthy individuals, in which a standardized menthol stimulus was developed alongside a sensory response tool. The menthol development studies demonstrated that increased cold pain sensitivity was associated with a change in the quality of the perceived sensation as well as increased intensity. A new scoring system, the Algotect Descriptor Index (ADI) was therefore developed that combined both intensity and quality response sub-scores. Visual analogue scale (VAS) scores for intensity of cold, heat, unpleasantness and pain were weighted according to their association with a more noxious response to cold. A list of descriptors was also weighted according to frequency of selection by cold hyperalgesic individuals and a Mean Word Score (MWS) calculated as the average value for words selected. The ADI was calculated as the sum of the VAS and MWS sub-scores (max 9). The ADI score was then assessed for its validity and reliability in two additional studies. The ADI showed a strong ability to discriminate between three sustained cold temperatures ranging from noxious (10°C), mildly unpleasant (15°C) to normally pleasant (20°C). Receiver operating characteristic curve analysis also showed that ADI was a good predictor of cold hyperalgesia, showing sensitivity of 0.90 and specificity of 0.74 at a cut-off of 4.5. Test-retest reliability for ADI with a 20% menthol stimulus was also high: ICC 0.945 (95% CI 0.878-0.975). This series of studies found that a simple, inexpensive, topical cold test can discriminate between individuals with and without cold hyperalgesia. The index has shown both construct validity and test-retest reliability in healthy populations.
Cold hyperalgesia assessment, the Algotect Descriptor Index (ADI), Visual analogue scale (VAS)