Somatosensory Profiles in Individuals With Persistent Musculoskeletal Pain and Inflammatory Bowel Disease

PPT will be assessed using an electronic handheld algometer (Wagner Force One™ FDIX) in: 1) low back (local), and 2) contralateral tibialis anterior. Individuals in "IBD with MSK pain" group will undergo an additional PPT assessment related to the region identified as their "main" area of MSK pain.

PPT will be assessed by a series of 3 ascending stimulus intensities given as a slowly increasing ramp (50 kilopascal (kPa/s)) from 0 to a maximum pressure of 1000 kPa. Pressure corresponding to the moment when participants identify that the sensation of pressure alone changing to one of pressure and pain, will be recorded for each trial. PPT for each region will be described as the mean of three trials in kPa. Decreased values indicates hypersensitivity of the nervous system.

CPM in the present study includes: PPT of tibialis anterior (test stimulus) and cold pressor test (CPT) to the contralateral hand (conditioning stimulus).

PPT will be performed and recorded as descried above prior to and immediately following CPT.

CPT: Hand will be submerged in an ice bath with the temperature maintained below 3°C for a maximum of 2 minutes. Participants will withdraw their hand when the pain perceived becomes intolerable or 2 minute maximum is reached. Participants will give a numeric pain rating (0-100) at the time of hand removal. Total immersion time (minutes:seconds) and pain rating will be recorded for CPT.

CPM (primary outcome) will be defined as the absolute numerical difference of PPT after minus before the CPT, with positive values indicating successful pain modulation.

Mechanical TS in the present study will be assessed by a wind-up-ratio (WUR) of the volar aspect of the non-dominant arm using a Semmes-Weinstein monofilament (no. 6.45). The perceived intensity of a single stimulus will be compared with that of a series of 10 repetitive stimuli of the same physical intensity. Participants will be asked to give a pain rating for the single stimulus and a pain rating for the series of 10 stimuli as a whole, using a '0-100' numerical rating scale. This procedure will be repeated for three trials, with 1 minute between trials, and performed at different areas of the volar forearm for each trial. The mean pain rating of the 10 series divided by the mean pain rating of the single stimuli will be calculated as WUR. Higher scores indicate greater mechanical TS, indicating an increase in central sensitivity or facilitation.

CSI is a self-report questionnaire indicating the presence of symptoms related to central sensitization syndromes. CSI consists of 25 statements where each statement is evaluated using a 5 point like scale with Never (0), Rarely (1), Sometimes (2), Often (3), and Always (4). This results in a cumulative score of 100. Scores equal to or greater than 40 indicate the likelihood of central sensitization.

Positive findings for abdominal pain interference, include: mild (50-59), moderate (60-69), or severe (≥70).

Numeric rating scales recorded for worst, average, and current pain levels, with positive findings as mild (1-4), moderate (5-6), or severe (7-10).

The EQ-5D questionnaire descriptive system comprises five domains (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression), each one with five possible levels: no problems (level 1), slight problems (level 2), moderate problems (level 3), severe problems (level 4), and extreme problems (level 5); as well as a visual analogue scale ranging from 0 to 100 with higher scores indicating 'best health'.

SCQ asks participants to reflect on any pain experienced during CPM testing, and to indicate the degree to which they experienced each of 13 thoughts or feelings during this experience, on 5-point Likert scales ranging from (0) not at all to (4) all the time. Total scores range from 0 to 24, with higher score representing greater pain catastrophizing.

This questionnaire includes words describing 10 positive and 10 negative emotions, and requires participants to indicate on a Likert scale (1-5) the extent for which they felt each emotion during the previous week, with higher sub-scores represent greater negative or positive affect styles, respectively.

The PSS-10 evaluates the degree to which individuals believe their life has been unpredictable, uncontrollable, and overloaded during the previous month, using a Likert scale (0-4) for each item, with higher scores representing greater perceived stress.

Scores for each subscale range from 0 to 21, with scores categorized as follows: normal 0-7, mild 8-10, moderate 11-14, and severe 15-21. Scores for the entire scale (emotional distress) range from 0 to 42, with higher scores indicating more distress.

Total comorbidity scores will be calculated as numerical disease counts using health conditions identified on the Self-Administered Comorbidity Questionnaire, a 20-item extraintestinal manifestation (EIM) checklist developed from multiple EIM investigations, and conditions identified on the central sensitization inventory (CSI) (part B). Scores range from 0 to 39 with higher scores indicating greater comorbidity.

Pain location will be recorded regionally (n=47) using a body diagram. Individuals with generalized pain will be categorically (yes/no) distinguished from those with regional pain using the modified widespread pain criterion which requires having pain in 4 out of 5 pain regions (4 quadrants plus axial pain).

Positive findings for the PROMIS Pain Interference 4a, include: mild (50-59), moderate (60-69), or severe (≥70).

Numeric rating scales for pain intensity will be recorded for worst, average, and current pain levels, with positive findings as mild (1-4), moderate (5-6), or severe (7-10)

EQ-5D is a standardized instrument for measuring of health-related quality of life. The EQ-5D consists of a descriptive system and the EQ VAS. The descriptive system comprises five dimensions (mobility, self-care, usual activities, pain/discomfort and anxiety/depression) each scored on a 5-point Likert scales ranging from (0) no problem to (4) severe. The EQ VAS records the patient's self-rated health on a 0 to 100 vertical visual analogue scale, with higher scores representing better health-related quality of life.

IBD subtype recorded from medical charts as Crohn's disease, ulcerative colitis, or unspecified IBD.

Time from initial IBD diagnosis - recorded from medical charts in years.

VDT will be assessed using a Rydel-Seiffer graded tuning fork (64 Hz, 8/8 scale) placed over bony prominences (styloid process of the ulna and medial malleolus), bilaterally. Participants will verbally indicate the moment they can no longer feel the sensation of vibration, and the value (1-8) will be recorded. VDT of each site will be described as the mean of three trials. Lower scores indicate decreased thresholds and possible peripheral neuropathy.

SWME of the upper limb will be performed using a 4.56 (4 g) monofilament at six locations divided over the palm and fingers, bilaterally. SWME of the lower limb will be performed using a 5.07 (10 g) monofilament at the pulp of the great toe, as well as the first, third, and fifth metatarsal heads, bilaterally. Participants will confirm (recorded as yes/no) application of the stimulus at each location. Incorrect response at any location indicates possible peripheral neuropathy.