Thermographic parameters in the diagnosis of secondary Raynaud's phenomenon

Objective: To determine the major infrared thermographic parameters in disc riminating between patients with and without secondary Raynaud's phenomenon . Design: A cross-sectional study. Setting: Outpatient clinic of a university department of physical medicine and rehabilitation in Vienna. Patients: Consecutive sample of 86 patients (72 women, 14 men) referred fro m the Division of Rheumatology for the clarification of a possible secondar y Raynaud's phenomenon. Main Outcome Measures: According to color changes induced by cold exposure, clinical classification of Raynaud's phenomenon was performed as follows: no, unlikely, probable, and definite Raynaud's phenomenon. The following th ermographic parameters were applied to a stepwise logistic regression analy sis: the absolute temperature of the fingertips before, 10, and 20 minutes after cold challenge (T-pre, T-10, T-20); the longitudinal temperature diff erence before, 10, and 20 minutes after cold challenge (LTDpre, LTD10, LTD2 0); the mean area under the rewarming curve of the fingertips; the recovery index 20 minutes after cold challenge (RI20); and the most rapid phase of rewarming of the fingertips of both hands (G(max) right, G(max) left). The sensitivity of thermographic classification into the 4 groups of clinical e valuation was assessed by discriminant analysis using significant parameter s from logistic regression analysis. Results: Only LTDpre reached the level of significance (p <.0001). Using LT Dpre, 22 of 23 subjects without clinical Raynaud's phenomenon and 20 of 26 patients with definite clinical Raynaud's phenomenon were classified correc tly. Patients with unlikely or probable Raynaud's phenomenon were classifie d as no Raynaud's phenomenon or definite Raynaud's phenomenon. Conclusion: LTDpre is the major thermographic parameter to discriminate bet ween patients with and without definite Raynaud's phenomenon by clinical hi story.