VALIDATION OF THERMOGRAPHY IN THE DIAGNOSIS OF REFLEX SYMPATHETIC DYSTROPHY

Objectives: To examine the validity of several thermogram-derived indi ces of autonomic functioning in the diagnosis of reflex sympathetic dy strophy (RSD). Design: A series of chronic pain patients were classifi ed diagnostically based on thermogram results using discriminant funct ion analysis, and validity measures (e.g., sensitivity, specificity) w ere used to determine the accuracy of computerized thermographic pixel analysis in discriminating RSD from other pathology. Setting: The stu dy was conducted at the Rush Pain Center, a multidisciplinary outpatie nt pain clinic. Patients: A series of 46 chronic pain patients referre d for suspected sympathetically mediated pain. Interventions: All pati ents underwent computerized thermographic examination under a baseline condition after acclimating to a climate-controlled room, immediately after a cold challenge was applied to the contralateral uninvolved ex tremity (4 degrees C for 90 s) and 20 min after the cold challenge. Ou tcome Measures: Temperature during the three experimental periods, deg ree of temperature asymmetry between affected and nonaffected limbs du ring the three periods, response to cold challenge, and recovery follo wing cold challenge were measured. Results: Temperature asymmetry accu rately discriminated between RSD and non-RSD patients, with the most a ccurate asymmetry measures obtained at baseline. Responses to cold cha llenge and actual temperature values did not discriminate between RSD and non-RSD pain patients. Conclusions: Thermography can be a useful c omponent of RSD diagnosis. In situations where sensitivity and specifi city are equally important, an asymmetry cutoff of 0.6 degrees C appea rs optimal. If specificity (i.e., accurately ruling out non-RSD cases) is more important, a cutoff of 0.8 degrees C or 1.0 degrees C may be considered as well.