Quantitative Sensory Testing (QST) - Does assessing ... - TI Pharma

4. QST and neuropathic pain mechanisms
shoulder: n=2, flank: n=2). Patients did not discontinue their regular pain treatment, if
applicable.
2.3. Quantitative sensory testing (QST)
The MPS testing procedures were applied according to the standardized protocol of
Rolke et al., 2006 (Rolke et al 2006a). QST was performed by two research nurses, who
underwent a comprehensive training at the DNFS in Germany. All tests were performed
at the same research facility of PRA International, Groningen, The Netherlands. The
average room temperature was 22.9°C; SD ± 1.9°C.
Mechanical pain sensitivity (MPS) was assessed using a set of seven pinprick devices
(flat contact area of 0.2 mm in diameter) with fixed stimulus intensities that exerted
forces of 8, 16, 32, 64, 128, 256, and 512 mN stimuli to obtain a stimulus–response
function for pinprick-evoked pain, which activates Aδ-nocipectors (Ziegler et al 1999).
A total of 35 pinprick stimuli were delivered. As part of the QST protocol, MPS test
was intermixed with the assessment of Dynamic Mechanical Allodynia (DMA). For
DMA, three innocuous dynamic allodynia tools, cotton wisp, cotton bud and brush
were applied (see Rolke et al., 2006) These stimuli were given in runs of 7 (five runs
each), and each run consisted of a different pseudorandom sequence of seven pinprick
stimuli and three dynamic allodynia stimuli. All stimuli were applied with a ~10 s
inter-stimulus interval – well below the critical frequency for wind-up (temporal pain
summation).
After each stimulus application, subjects were asked to give a pain rating for each
stimulus on a ‘0–100’ numerical rating scale (NRS) (‘0’ indicating ‘‘no pain’’, and ‘100’
indicating ‘‘most intense pain imaginable’’).
2.4. Data analysis and statistics
2.4.1. Z-transformation of QST data
Pain rating to the seven different intensities of punctuates mechanical stimuli obtained
from healthy subjects and patients are expressed as arithmetic mean and 95% confidence
intervals. Both, patients and healthy subjects were divided into two age groups each
(25-44 years of age and 45-74 years of age). MPS data of patients with neuropathic pain
were compared with reference data from gender and age matched healthy subjects. QST
values of neuropathic pain locations at the upper extremities were compared to QST
reference values obtained from the dorsal hand of healthy controls, whereas values
from neuropathic pain locations at lower extremities were compared to reference values
obtained from the dorsal foot of healthy controls. MPS values from each patient were
transformed to z-scores as described by Rolke et al., 2006 (Rolke et al 2006a). A score
above 1.96 or below -1.96 falls outside the 95% confidence interval of the mean reference
value and was considered as a sensory abnormality. Abnormalities were subsequently
categorised as either a sensory gain or a sensory loss.