Quantitative sensory testing: a comprehensive protocol for clinical trials

Abstract

We have compiled a comprehensive QST protocol as part of the German Research Network on Neuropathic Pain (DFNS) using well established tests for nearly all aspects of somatosensation. This protocol encompasses thermal as well as mechanical testing procedures. Our rationale was to test for patterns of sensory loss (small and large nerve fiber functions) or gain (hyperalgesia, allodynia, hyperpathia), and to assess both cutaneous and deep pain sensitivity. The practicality of the QST protocol was tested in 18 healthy subjects, 21–58 years, half of them female. All subjects were tested bilaterally over face, hand and foot. We determined thermal detection and pain thresholds including a test for the presence of paradoxical heat sensations, mechanical detection thresholds to von Frey filaments and a 64‐Hz tuning fork, mechanical pain thresholds to pinprick stimuli and blunt pressure, stimulus‐response‐functions for pinprick and dynamic mechanical allodynia (pain to light touch), and pain summation (wind‐up ratio) using repetitive pinprick stimulation. The full protocol took 27 − 2.3 min per test area. The majority of QST parameters were normally distributed only after logarithmic transformation (secondary normalization) except for the frequency of paradoxical heat sensations, cold and heat pain thresholds, and for vibration detection thresholds. Thresholds were usually lowest over face, followed by hand, and then foot. Only thermal pain thresholds, wind‐up ratio and vibration detection thresholds were not significantly dependent on the body region. There was no significant right‐to‐left difference for any of the QST parameters; left‐to‐right correlation coefficients ranged between 0.78 and 0.97, thus explaining between 61% and 94% of the variance. This study has shown that a complete somatosensory profile of one affected area and one unaffected control area, which will be necessary to characterize patients with a variety of diseases, can be obtained within 1 h. Case examples of selected patients illustrate the value of z‐transformed QST data for an easy survey of individual symptom profiles.