The spoon test: a valid and reliable bedside test to assess sudomotor function

Objective: To establish the validity of bedside sudomotor tests in a controlled prospective study. Methods: Five different tests were used to assess presence of sweating at seven bilaterally symmetrical body loci, namely, examination with the unaided eye, visualization with light reflection, magnification with an ophthalmoscope, palpation of skin for slickness, and gliding the back of a spoon over the skin to detect friction. Sensitivity and specificity of these bedside tests were compared with the thermoregulatory sweat test in 130 subjects with generalized body sweating and 16 patients with complete anhidrosis. Results: The spoon test was more sensitive in detecting sweating than the other four bedside tests, demonstrating sensitivity of about 86% at the neck, 58% at the chest, and 51% at the forehead. Specificity of the spoon test was almost 100% at all body sites except at the chest (81%) and the neck (50%). Interpretation: With caveats related to methodology, the spoon test is a clinically practical and useful bedside screening test for the assessment of sweating, especially at the forehead and chest.