Comparative study of the cutaneous sensation of leprosy-suspected lesions using Semmes-Weinstein monofilaments and quantitative thermal testing

The objective of the present study was to compare the warm cold perception thresholds (WPT), cold perception thresholds (CPT) and the warm and cold perception interval (WCPI) determined in our previous study with the touch-pressure thresholds, in leprosy-suspected skin lesions (‘patch’). Thermal testing was conducted using a thermal sensory analyser TSA-2001 (Medoc Ltd., Israel) and the method of levels. The touch-pressure thresholds were measured using Semmes-Weinstein monofilament (SWM) of 0-05 g, 0.2 g, 2 g, 4 g, 10 g and 300 g. A cross-sectional study of 112 patients presenting with leprosy-suspected skin lesions, with no clinical evidence of peripheral nerve damage, was conducted. Leprosy diagnoses were based on clinical dermato-neurological examinations. 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 aetiologies. The SWM test showed a sensitivity of 81.7% and a specificity of 96.1%, while the warm and cold perception thresholds presented sensitivity of 90.2% and 92-2%, respectively (both with 100% specificity). In leprosy patients, lesions that exhibited pressure thresholds of 0.05 g typically showed significantly different WPT, CPT and WCPI values when compared with skin lesions of different aetiologies. Within the leprosy group, the mean values of WPT, CPT and WCPI increased according to the increase in touch-pressure thresholds. Some of the patients exhibiting leprosy lesions with touch-pressure thresholds of 0-05 and 0-2 g presented normal WPT or CPT values. However, all patients with SWM equal or above 2.0 g presented altered WPT and CPT. All patients with leprosy, including those that exhibited pressure thresholds of 0.05 g, presented altered WCPI in the skin lesions. Despite a higher sensitivity to thermal tests, the SWM has adequate validity as a screening tool in the diagnosis of cutaneous forms of leprosy and in the selection of patients who should be submitted to a more detailed examination.