2016 – Thermoregulatory Sweat Test (TST)
Author(s):Robert D. Fealey
The thermoregulatory sweat test (TST) consists of giving a controlled heat and humidity stimulus to produce a generalized sweat response. The TST assesses the integrity of efferent sympathetic sudomotor pathways. The entire anterior body surface is tested for both pre- and post-ganglionic lesions. The TST can evaluate patients with symptoms of small-fiber neuropathy and demonstrate autonomic involvement in disorders such as multiple system atrophy, hyperhidrosis, and some skin disorders. An indicator powder placed on the body surface before heating provides visualization of sweating and non-sweating skin. The patient’s weight (before and after heating) and height allows calculation of total body sweat rate, and the slope of the core temperature rise with time provides an estimate of heat tolerance. Normal and abnormal TST patterns, report generation, and difficulties and pitfalls in test interpretation are described.