Quantitative sweat testing using acetylcholine for direct and axon reflex mediated stimulation with silicone mold recording; controls versus neuropathic diabetics.

Sweat glands were stimulated by iontophoresed acetylcholine (ACh). Using a two-chamber capsule, one group of sweat glands was stimulated directly by ACh, and another stimulated indirectly via axon reflexes. Sweat droplets were recorded with a silicone mold and counted by a dissecting microscope and a computerized scanner. Responses from 32 diabetics with generalized somatic peripheral neuropathy were compared with 32 controls. Counting sweat droplets by computerized scanning was more accurate than by microscope. The numbers of droplets, their total areas, and mean areas were all larger in the direct response. Counts of droplet numbers was more diagnostically useful than measuring the total area and the mean areas of the droplets. There was a high correlation between droplet numbers of the direct and the indirect sweat responses. Droplet number counts of the direct response had a slightly higher diagnostic yield than those of the technically more complicated indirect response: for a specificity of 95%, the direct response had a sensitivity of 55%, the indirect being 50%.