Objective: To determine the major infrared thermographic parameters in discriminating 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 from the Division of Rheumatology for the clarification of a possible secondary 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 thermographic parameters were applied to a stepwise logistic regression analysis: the absolute temperature of the fingertips before, 10, and 20 minutes after cold challenge (Tpre, T10, T20); the longitudinal temperature difference before, 10, and 20 minutes after cold challenge (LTDpre, LTD10, LTD20); 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 (Gmax right, Gmax left). The sensitivity of thermographic classification into the 4 groups of clinical evaluation was assessed by discriminant analysis using significant parameters from logistic regression analysis.
Results: Only LTDpre reached the level of significance (p < .0001). Using LTDpre, 22 of 23 subjects without clinical Raynaud's phenomenon and 20 of 26 patients with definite clinical Raynaud's phenomenon were classified correctly. Patients with unlikely or probable Raynaud's phenomenon were classified as no Raynaud's phenomenon or definite Raynaud's phenomenon.
Conclusion: LTDpre is the major thermographic parameter to discriminate between patients with and without definite Raynaud's phenomenon by clinical history.