Impaired warm and cold perception thresholds in leprosy skin lesions

The aim of the present study was to determine the frequency of alteration in warm perception thresholds (WPT), cold perception thresholds (CPT) and the warm and cold perception interval (WCPI) in leprosy-suspected skin lesions, and to determine if these tests could assist in the diagnosis of leprosy. Tests were conducted using a thermal sensory analyser TSA-2001 (Medoc Ltd, Israel) and the method of levels. A cross-sectional study of 112 patients presenting leprosy-suspected skin lesions ('patch'), with no clinical evidence of peripheral nerve damage, was conducted. Leprosy diagnosis was based on clinical dermato-neurological examinations and complementary tests. One hundred and eight subjects (45 males, 63 females; average age 37.7 years) completed the tests: 82 were positively diagnosed with leprosy and 26 with diseases of different etiologies. The mean values of WPT (45-63 +/- 5.59), CPT (9.64 +/- 11.34) and WCPI 36.01 +/- 15.58) registered in leprosy-skin lesions were significantly different (P < 0.001) from lesions of diverse aetiologies and skin area without lesions. The cut-off point for WPT as determined from the ROC curve (receiver operating characteristic) was 35-10 degrees C, with a sensitivity of 90.2% and a specificity of 100%, and the corresponding cut-off point for CPT was 28.95 degrees C, with a sensitivity of 92.7% and a specificity of 100%. Nevertheless, all patients with leprosy presented a WCPI greater than 6.10 degrees C (ROC curve) in skin lesions. Increase in the thermal thresholds indicated warm hypoaesthesia, cold hypoaesthesia or both. The WCPI, which embraces both warm and cold perception thresholds, was the best indicator of thermal sensation, a term used in literature as a non-specific expression that does not describe warm and cold stimuli explicitly in terms of units of temperature.