1 The Pain in Neuropathy Study (PiNS): A cross-sectional observational study determining the somatosensory phenotype of painful and painless diabetic neuropathy Supplementary materials
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The Pain in Neuropathy Study (PiNS): A cross-sectional observational study
determining the somatosensory phenotype of painful and painless diabetic neuropathy
Supplementary materials
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Supplementary methods
Neuropathy screening tools, symptom and function questionnaires
A set of questionnaires assessing the presence of pain, pain intensity, pain distribution and the
psychological and functional impact of pain were either completed before the appointment, or
after the appointment and then returned to the study centre by post .
Patients were asked to keep a pain intensity diary for 7 days, recording pain at 9 am and 9 pm
daily on an 11 point scale, with 0 being no pain and 10 the worst pain imaginable. Study
participants also completed a body map highlighting the distribution of pain.
Toronto Clinical Scoring System (TCSS) is a screening tool for diabetic peripheral
neuropathy, and correlates with diabetic neuropathy severity. The TCSS uses a simplified
neurological examination assessing peripheral sensory perception, deep tendon reflexes, and
the presence of neuropathy symptoms. Deep tendon reflexes scores are graded for each side
as loss, 2; reduced, 1; and normal, 0. The presence of each following neuropathy symptoms is
assigned 1 point: pain, numbness, tingling and weak-ness in the feet, the presence of similar
upper limb symptoms, and the presence of unsteadiness on ambulation. Sensory testing is
performed on the first toe for the following: pinprick sensation, temperature discrimination,
proprioception, light touch, and vibration, performed at the first toe. Responses were rated as
normal or abnormal and were assigned 0 or 1 point, respectively. Scores range from 0 to 19.
The Douleur Neuropathique en 4 Questions (DN4) is a screening tool for neuropathic pain.
DN4 consists of 10 items grouped into four questions: seven items relating to the pain
description (burning, painful cold, electric shocks) and to its associated abnormal sensations
(tingling, pins and needles, numbness, itching) and the other three items relating to a brief
bedside neurological examination in the painful area (touch hypoaesthesia, pinprick
hypoaesthesia, tactile dynamic allodynia). For scoring, 1 is given to each positive and 0 to
each negative item and the total score range 0–10.
The PainDETECT contains nine items, of which seven relate to sensory responses and two to
the temporal and spatial characteristics of the pain pattern. By rating the seven items from
never (0) to very strongly (5) on a category scale and summing these with the scores for
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temporal (−1 to +1) and spatial characteristics (0 or +2), a summary score (minimum −1,
maximum 38) was obtained. A total score of <13 indicates that a neuropathic component is
unlikely, whereas a score of >18 indicates that a neuropathic component is likely.
Brief Pain Inventory (BPI) pain interference and pain severity subscales were used to asses
any type of pain (non-neuropathic and neuropathic) that study participants experience. Pain-
related interference in activities of daily living was assessed using the 7-item Pain
Interference scale of the BPI. The scale assesses pain interference within 7 domains: general
activity, walking, work, relationships, mood, life enjoyment, and sleep. Study participants
score these on a 11 point scale ranging from 0 (does not interfere) to 10 (completely
interferes). The composite score was calculated as the sum of the 7 interference items.
Neuropathic Pain Symptom Inventory (NPSI) is a self-administered questionnaire designed to
evaluate neuropathic pain symptoms. The NPSI was completed for pain in feet and hands. It
evaluates the presence and severity of 10 different neuropathic pain descriptors, each on an
11 point scale where 0 indicates no symptoms and 10 indicates maximal symptoms
experienced. The NPSI also includes 2 temporal items assessing the duration of spontaneous
ongoing pain, and the number of pain attacks on 5-point categorical scales.
Overall Neuropathy Limitation Scale (ONLS) is a scale that measures the limitation of
everyday activities within the upper and lower limbs, It is separated into two scales for the
arm and legs respectively that determines if the activities of daily living are not affected,
affected but not prevented or prevented. A higher score indicates a greater degree of
disability.
Pain Catastrophizing Scale (PCS) assessed the cognitive process by which pain is appraised
in terms of threat and negative consequences. It consists of 13 descriptions of thoughts and
feelings related to pain. Study participants are asked to indicate the degree to which they
experience these on a 5-point rating scale from 0 (not at all) to 4 (always). A high total score
indicates a high level of pain catastrophizing. PCS comprises 3 dimensions: rumination,
magnification, and helplessness. Rumination refers to the patients’ preoccupation with pain;
magnification expresses the exaggerated cognitions of pain as a threat; and hopelessness is
patients’ feelings that they are unable to influence their pain.
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Depression Anxiety Positive-Outlook instrument (DAPOS) was used to measure mood and
consists of 3 subscales. The subscale for depression contains 5 items with scores ranging
from 5 to 25, indicating normal mood to severe depression. The subscale for anxiety contains
3 items, which ranges from 3 to 15, indicating no anxiety to maximal anxiety. The subscale
for positive outlook contains 3 items, which ranges from 3 to 15, indicating poor positive
outlook to good positive outlook.
Pain Anxiety Symptom Scale 20 (PASS-20) assesses pain-related anxiety and is a shortened
version of the PASS. PASS-20 has 20 questions assessing 4 facets of pain-related anxiety:
fearfulness of pain, cognitive anxiety, escape/avoidance, and psychological anxiety. Each
subscale score ranges from 0 (no interference) to 25 (maximum interference). Additionally,
summation of the subscales provides a general measure of pain-related anxiety.
Survey of Autonomic Symptoms (SAS) is an instrument that measures the presence and
impact of autonomic symptoms. It consists of 12 questions that are individually rated on a 6-
point rating scale from 0(not at all) .to 5 (a lot).
Insomnia Severity Index (ISI) measured the study participant’s perception, subjective
symptoms, and consequences of any sleep disturbances. The ISI is composed of 7 items
assessing the severity of sleep onset and sleep maintenance difficulties, satisfaction with
sleep patterns, interference with daily functioning, noticeability of impairment due to sleep
dysfunction, and the degree of distress experienced by the patient. Its content corresponds, in
part, to the diagnostic criteria of insomnia
Short Form 36 of the MOS Outcomes Study (SF-36) assess health-related quality of life. SF-
36 responses were scored in the 8 domains of physical functioning: role–physical, bodily
pain, general health, vitality, social functioning, role–emotional, and mental health. SF-36
scores range from 0 to 100, representing extreme dysfunction/symptom severity to optimal
function, respectively.
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Supplementary figure legends
Supplementary figure 1
a) Scatter plot and mean ± 95% CI of z-scores for Thermal QST parameters in study
participants with no diabetic peripheral neuropathy and those with diabetic peripheral
neuropathy
Unpaired t-tests: *P < 0.05; ** P < 0.01.
WDT- Warm Detection Threshold, CDT – Cold Detection Threshold, TSL - Thermal
Sensory Limen; Cold Pain Threshold; Heat Pain Threshold.
b) Scatter plot and mean ± 95% CI of z-scores for Mechanical QST parameters in study
participants with no diabetic peripheral neuropathy and those with diabetic peripheral
neuropathy.
Unpaired t-tests: * P < 0.05; ** P < 0.01.
MDT- Mechanical Detection Threshold; VDT- Vibration Detection Threshold; MPT-
Mechanical Pain Threshold; MPS- Mechanical Pain Sensitivity; WUR- Wind-up ratio; PPT-
Pressure Pain Threshold
Supplementary figure 2
a) Scatter plot and median (interquartile range) of Warm Sensibility Index for study
participants with no diabetic peripheral neuropathy compared to diabetic peripheral
neuropathy. Mann-Whitney U Test: ** P < 0.01
Scatter plot and median (interquartile range) of Warm Sensibility Index for study participants
with diabetic neuropathy and no neuropathic pain, mild neuropathic pain, moderate/severe
neuropathic pain. Kruskal-Wallis, Dunn's multiple comparison test.
b) Scatter plot and median (interquartile range) of Cold Sensibility Index for study
participants with no diabetic peripheral neuropathy compared to diabetic peripheral
neuropathy. Mann-Whitney U Test: ** P < 0.01
Scatter plot and median (interquartile range) of Cold Sensibility Index for study participants
with diabetic neuropathy and no neuropathic pain, mild neuropathic pain, moderate/severe
neuropathic pain. Kruskal-Wallis, Dunn's multiple comparison test: * P < 0.05.
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Supplementary Table 1
Summary of all drugs used
Data shown as values and percentages and analysed by χ2 squared test of association.
Symbols reflect the differences between the respective groups:
† P < 0.05, †† P < 0.01 between No Neuropathic Pain and Moderate/Severe Neuropathic Pain
# P < 0.05, between Mild Neuropathic Pain and Moderate/Severe Neuropathic Pain
‡‡ P < 0.01 between No Neuropathic Pain and Mild Neuropathic Pain
Supplementary Table 2
Summary of clinical scores, electrophysiological recordings from lower limbs of study
participants with no peripheral neuropathy and diabetic peripheral neuropathy with no
neuropathic pain, mild neuropathic pain, moderate/severe neuropathic pain.
Nerve conduction study interpretations were available for 175 (84%) and IENFD results were
available for 146 study participants (69%).
Data shown as median (interquartile range) and analysed by Kruskal-Wallis, Dunn's multiple
comparison test.
TCSS- Toronto Clinical Scoring System
Symbols reflect the differences between the respective groups:
† P < 0.05, †† P < 0.01 between No Neuropathic Pain and Moderate/Severe Neuropathic Pain
‡‡ P < 0.01 between No Neuropathic Pain and Mild Neuropathic Pain
¶¶ P < 0.01 between No DPN and DPN (across all groups with Neuropathic Pain)
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No Neuropathic
Pain
Mild Neuropathic
Pain
Moderate/Severe
Neuropathic Pain P
Number of participants 80 41 70
Reported drug use 79 39 70
All oral hypoglycaemic agents 65 (82.3%) 30 (76.9%) 48 (73.8%) 0.19
Metformin 64 (81.0%) 29 (74.4%) 45 (69.2%) 0.09
Other Oral hypoglycaemic
(Gliclazide) 33 (41.8%) 13 (33.3%) 16 (24.6%) 0.06
Insulin 31 (39.2%) 17 (41.5%) 34 (52.3%) 0.51
Other agents (Sitagliptin,
Pioglitazone, Exanatide,
Linagliptin)
20 (25.3%) 5 (12.8%) 18 (27.7%) 0.12
Statin 51 (64.6%) 35 (89.7%) ‡‡ 49 (75.4%) # < 0.01
Aspirin 35 (44.3%) 13 (33.3%) 24 (36.9%) 0.37
Anti-Hypertensives 66 (83.5%) 29 (74.4%) 47 (72.3%) 0.12
ACE-I 60 (75.9%) 24 (61.5%) 42 (64.6%) 0.12
Diuretic 16 (20.3%) 15 (38.5%) 17 (26.2%) 0.12
B-blocker 19 (24.1%) 7 (17.9%) 6 (9.2%) † 0.04
Calcium channel blocker 24 (30.4%) 10 (25.6%) 15 (23.1%) 0.52
Thyroxine 10 (12.7%) 3 (7.7%) 5 (7.7%) 0.48
PPI 12 (15.0%) 8 (20.5%) 24 (36.9%) †† 0.02
Supplementary Table 1
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No Diabetic
Neuropathy
No
Neuropathic
Pain
Mild
Neuropathic
Pain
Moderate/
Severe
Neuropathic
Pain
P
Number of participants 18 80 41 70
TCSS
Total Score
1 ¶¶
(0-3)
8
(5-10)
10 ‡‡
(8-13)
11 ††
(8-14) < 0.01
TCSS
Symptom
sub-score
0 ¶¶
(0-1)
1
(1-2)
3 ‡‡
(1-3.5)
3 ††
(2-4) < 0.01
TCSS Examination
sub-score
0 ¶¶
(0-2)
7
(4-8.8)
8
(6-9.5)
8 †
(5.8-11) < 0.01
MRC Sensory Sum
Score 0 ¶¶
6
(2-11)
8
(6-13)
11 ††
(5-18) < 0.01
IENFD (fibres/mm) 5.0 ¶¶
(3.4-6.4)
1.2
(0.4-1.9)
0.8
(0.4-1.7)
1.0
(0.3-1.8) 0.58
Sural nerve
Amplitude (μV) 8.4 ¶¶
(6.3-14.9)
1.0
(0.0-4.0)
0.0
(0.0 -3.5)
1.7
(0.0-5.2) 0.74
Conduction velocity
(m/s)
44.4 ¶¶
(40.6-47.3)
38.9
(33.7-43.2)
41.1
(34.3-45.9)
38.7
(36.3-43.6) 0.78
Peroneal nerve
Amplitude (mV) 4.0 ¶¶
(3.3-5.4)
1.9
(0.5-4.1)
1.4
(0.1-3.5)
0.7
(0.0-2.5) 0.07
Conduction velocity
(m/s)
44.9 ¶¶
(40.4-48.5)
40.1
(35.5-43.3)
39.1
(36.7-43.0)
35.5
(31.8-41.5) 0.20
Supplementary Table 2