Results
A total of 313 individuals with diagnosed ME/CFS underwent HUT during
the study period. PPT testing was not performed due to increased
severity of hand pain (often in those with hypermobile joints) (n=50);
15 patients refused PT testing. None of the patients used HR or BP
altering drugs before the measurements. This left 248 females to be
analyzed. One-hundred-sixty-four patients (66%) fulfilled the criteria
for FM, eighty-four (34%) did not. As part of the ME/CFS criteria,
patients were asked for the presence of muscle complaints. In the group
of ME/CFS patients without FM 59/84 (70%) reported muscle pains. In
ME/CFS patients with FM, all patients 164/164 (100%) reported muscle
pains.
Table 1 shows the demographic characteristics of the study population.
The NRS pain score was significantly different between the three groups
(p all <0.0001). ME/CFS patients with and without FM showed
higher supine heart rates compared to HC (p<0.0005 and
p<0.002, respectively) and higher EOS heart rates compared to
HC (both p<0.0001). No other variables were significantly
different.
Table 2 shows PPT pre- and post-HUT for the finger and the shoulder. PPT
of HC were all significantly higher than of ME/CFS patients (p ranging
between <0.005 and <0.0001), except for PPT of the
finger in ME/CFS patients without FM (p=0.41). Ninety-six ME/CFS
patients (38%) used neuropathic pain medication, 14/84 (17%) in
patients without FM and 82/164 (50%) in patients with FM. A subgroup
analysis showed no differences in PPT between ME/CFS patients with FM
using neuropathic pain medication compared to those without. Similarly,
no differences in PPT were found between ME/CFS patients without FM
using neuropathic pain medication or not (data not shown). Figure 1
shows PPT pre- and post-HUT for the finger and the shoulder in HC (panel
A), in ME/CFS patients without FM (panel B), and in ME/CFS patients with
FM (panel C). PPT of the finger were significantly higher than PPT of
the shoulder in all 3 groups (all p<0.0001). PPT of HC did not
differ pre- and post-HUT for both the finger and the shoulder (p=0.14
and p=0.54, respectively). In both ME/CFS patient groups there was a
significant difference pre- and post-HUT for both the finger and the
shoulder (p ranging between 0.0001 and <0.0001). PPT of ME/CFS
patients with FM were significantly lower than PPT of ME/CFS patients
without FM (all p<0.0001).
Figure 2 shows the graphical representation of the regression line in
the 3 groups for the finger (panel A) and the shoulder (panel B). For
all time points and groups, the linear regression of windup from
stimulus one to ten on both finger and shoulder were highly significant
(p ranging from 0.0003 to <0.0001). The slopes of the
regression lines pre- and post-HUT for both ME/CFS patient groups were
significantly higher than the slopes of the pre- and post-HUT
regressions lines of HC (all p<0.0001). There was no
difference in the regression line slopes between pre- and post-HUT
within the 3 groups for both the finger and the shoulder. For comparison
with the published literature, stimulus 1 pain values were subtracted
from stimulus 10 pain values to create a delta windup value. As shown in
Figure 3, for both the finger and the shoulder, delta windup values did
not differ between pre- and post-HUT in HC and the 2 ME/CFS patient
groups. For both locations a statistically significant difference was
found between HC and the 2 ME/CFS patient groups (both
p<0.0001).