sweating; however, it utilizes an automated imaging analysis software that is less technically complex. prior to iontophoresis, the skin is dried and covered with an indicator dye consisting of povidone-iodine mixed with corn starch and mineral oil. the indicator dye changes color with the onset of sweating. digital photographs of the color change are recorded every 15 seconds over approximately 7 minutes. spatial and temporal analysis of sweat droplets as well as direct and indirect sweat response are measured. although qdirt is less technically demanding than qsart or tst, it still requires trained staff and an environmentally controlled room; iontophoresis may cause skin irritation or burning; the skin areas studied using qdirt are not pre-defined, thus limiting the interindividual comparability of the test; and little normative or performance data are available. sensitive sweat test (sst) the sst was recently developed by adam loavenbruck and colleagues in 2017 for the evaluation of individual sweat glands. it allows for the quantification of sweat from each individual sweat gland, as well as their location and distribution, thus providing both temporal and spatial resolution. the procedure is initiated by the iontophoresis of 0.5% pilocarpine solution over a 2.25 cm2 skin area, which stimulates the underlying sweat glands directly through the activation of muscarinic m3 receptors. immediately following iontophoresis, the skin is dried, and then covered with a 10% povidone-iodine solution. at the onset of sweating, the reaction of sweat with the povidone-iodine solution and corn starch results in the appearance of a black spot. a customized miniature camera can follow the secretions of up to 400 sweat glands at a time for up to 60 seconds, analyzing the enlargement rate and area of each spot. the test is then repeated for replicate analysis. the procedure is relatively quick and the camera is portable. however, further testing is needed to establish normative data and to confirm its utility in autonomic testing. as the test lacks an axon-reflex response, it has a limited ability to assess nerve fiber function. sympathetic skin response (ssr) ssr refers to the change in skin resistance to electrical conduction associated with the sympathetic activation of sudomotor function in response to external or internal stimuli, such as electrical stimulation, deep breathing, and mental stress. it is mediated by a poorly understood somato-sympathetic reflex with spinal, bulbar, and suprabulbar components. the ssr is frequently utilized in psychophysiological studies and is a well-known component of the polygraph test. the test is performed using standard electromyography (emg) equipment in a lightly dimmed, humidity- and temperature-controlled room. a surface electrode is positioned on the patient’s palm or sole, along with a reference electrode on the dorsal side of the same body area. a change in skin potential is then induced either through electrical stimulation or deep breathing. the recorded ssr is then plotted on a graph and analyzed for presence or absence, latency, and amplitude. the ssr is thought to be mainly influenced by the electrolyte content of sweat secreted from eccrine glands. in addition, there is significant intra-individual and inter-individual variability, and ssr declines with age and is commonly absent in individuals over the age of 50. ssr is only considered a surrogate marker of sudomotor function and its results should be interpreted in the context of other sudomotor testing. spoon test the spoon test, developed in 1964 by dr. ernest bors, relies on assessment of the smooth movement of the convex side of a spoon along the surface of the patient’s skin. in patients with sudomotor dysfunction, the spoon will slide in a smooth and uninterrupted fashion. conversely, the spoon’s movement in normal controls will be frequently interrupted by the presence of sweat on the skin. the spoon test is inexpensive, easy to perform, but subjective and not quantitative. sweat gland nerve fiber density (sgnfd) sgnfd can be quantified in skin biopsies taken from the distal leg, distal thigh, and proximal thigh prepared for standard analysis of intraepidermal nerve fiber density (ienfd). nerve fibers innervating sweat glands are stained with protein gene product 9.5 and quantified using manual morphometry with light microscopy. sgnfd can potentially be used as a surrogate anatomical marker for sudomotor function. however, it is not a direct assessment of the sweat response, and normative data must be established. minor's test main article: minor test physical examination inspection of the patient’s skin, particularly on the lower extremities, in conjunction with a thorough medical history, can provide valuable information regarding the possible presence of sudomotor dysfunction. evidence of altered skin hydration, such as hyperkeratosis, excessive skin dander, rhagades, and ulcers, can be suggestive of sudomotor dysfunction. presence of intense foot odor may be another presentation.