Quantitative sensory testing: a diagnostic tool for painful neuropathy

Quantitative sensory testing (QST) analyzes sensory perceptions of external stimuli of controlled intensity. Both large and small fiber function can be evaluated by applying thermal and mechanical stimuli, thus closing the diagnostic gap for the conventional electrophysiology in the examination of thin and unmyelinated nerve fibers. Detection, pain thresholds and stimulus–response curves can be determined; therefore, QST is a valuable diagnostic tool for identifying both sensory loss (i.e., hypoesthesia and hypoalgesia) and gain (i.e., hyperalgesia and allodynia) in patients with painful or painless neuropathy. Every psychophysical approach QST requires standardized stimuli administration, instructions and data evaluation to achieve valid results. QST can be used to evaluate distinct somatosensory profiles and thus give hints to the underlying mechanisms that occur with different frequencies in different pain syndromes. This might be helpful for the future establishment of mechanism-based pharmacotherapy. Since normative data are available, QST also contributes to the individual diagnosis of neuropathy. The present article gives an outline of QST application in diagnosis and its limitations for the evaluation of neuropathic pain.