Reliability of quantitative sudomotor axon reflex testing and quantitative sensory testing in neuropathy of impaired glucose regulation

Abstract

Reproducible neurophysiologic testing paradigms are critical for multicenter studies of neuropathy associated with impaired glucose regulation (IGR), yet the best methodologies and endpoints remain to be established. This study evaluates the reproducibility of neurophysiologic tests within a multicenter research setting. Twenty-three participants with neuropathy and IGR were recruited from two study sites. The reproducibility of quantitative sudomotor axon reflex test (QSART) and quantitative sensory test (QST) (using the CASE IV system) was determined in a subset of patients at two sessions, and it was calculated from intraclass correlation coefficients (ICCs). QST (cold detection threshold: ICC=0.80; vibration detection threshold: ICC=0.75) was more reproducible than QSART (ICC foot=0.52). The performance of multiple tests in one setting did not improve reproducibility of QST. QST reproducibility in our IGR patients was similar to reports of other studies. QSART reproducibility was significantly lower than QST. In this group of patients, the reproducibility of QSART was unacceptable for use as a secondary endpoint measure in clinical research trials.

Figure 1

A. Reproducibility of VDT between individual tests (T1-6) and trials in subjects with impaired glucose tolerance and small fiber neuropathy. The box plot indicates the mean, 25^th and 75^th percentiles for VDT expressed in JND units for each test. B. Reproducibility of CDT between individual tests (T1-6) and trials in subjects with IGR and neuropathy. The box plot indicates the mean, 25^th and 75^th percentiles for CDT results expressed in JND units for each test.