Keywords
complex regional pain syndromes - fracture fixation - interview, telephone - pain
- surveys and questionnaires
Introduction
Neuropathic pain is “a pain arising as a direct result of an injury or disease affecting
the somatosensory system.”[1] Neuropathic pain-associated factors include the female gender and advanced age.[2] Recent studies also reported that fracture and surgery are a common etiology for
neuropathic pain.[3]
[4]
Although epidemiological data on neuropathic pain remains not detailed in the literature,
it has evolved in recent years.[5] In Brazil, its estimated prevalence in patients with chronic pain and neuropathic
characteristics is 14.5%.[6]
Among the tools for neuropathic pain screening, the Douleur Neuropathique 4 (DN4) questionnaire is more practical than others as it has fewer items and a high
capacity to discriminate neuropathic pain from nociceptive pain.[7]
[8] DN4, developed by the French neuropathic pain group, contains ten items answered
as yes or no; a score equal to or higher than four indicates the presence of neuropathic
pain.[9] In addition, the DN4 interview (DN4i) has the initial seven items alone, and a positive
score is equal to or higher than 3.[9] Santos et al.[7] validated and translated the DN4 into Brazilian Portuguese.
Fast, highly sensitive tools for detecting neuropathic pain, whether used in person
or not, allow a detailed determination of epidemiology and etiology, appropriate choice
of therapeutic interventions, and prognostic definition. Therefore, this study aimed
to compare the results obtained through the in-person application of the DN4 questionnaire
and the DN4i administered via telephone to identify neuropathic pain after fracture
surgery.
Materials and Methods
This study is methodological and based on medical records of patients undergoing fracture
surgery in our hospital from January 2017 to July 2020. The Research Ethics Committee
approved this study under number (CAAE: 28504919.5.0000.5134).
This study used a convenience sample and recruited all patients meeting the eligibility
criteria, i.e., aged 18 or over undergoing fracture surgery in our hospital and who
signed the Informed Consent Form (ICF) and could attend the hospital's Orthopedics
and Traumatology department. Patients who refused to participate in the study, did
not answer the phone call, or died were excluded.
A previously trained group of orthopedists from our clinical staff applied the validated
DN4 translated into Brazilian Portuguese to patients in person. After 4 to 6 months,
two researchers unaware of the results obtained by orthopedists administered the DN4i
questionnaire by telephone to their respective patients. All collected data was organized
in an Excel spreadsheet for later analysis.
The DN4 questionnaire has two parts. The first part is an interview with seven items,
while the second is a sensory examination with three items. DN4i contains only the
interview, allowing self-application by the patient or telephone use. The seven-item
part encompasses two domains: the first evaluates the characteristics of the pain
(burning, painful cold sensation, and electric shock), and the second assesses symptoms
associated with abnormal sensations in the same area (tingling, pins and needles,
numbness, and itching). The second part of DN4, the sensory examination, addresses
hypoesthesia to touch, hypoesthesia to needle prick, and pain caused or increased
by brushing. Each item in both questionnaires is answered as “yes” (equivalent to
1) or “no” (equivalent to 0). The sum of the scores can range from 0 to 10 for DN4,
and from 0 to 7 for DN4i. A score positive for neuropathic pain corresponds to a sum
≥ 4 for DN4 and ≥ 3 for DN4i.[9]
An independent investigator performed the analysis. Descriptive statistics characterized
the sample considering all variables collected. These data were presented as measures
of central tendency (mean/median) and dispersion (standard deviation) for quantitative
variables and frequency and percentage for categorical variables.
The Pearson's correlation coefficient investigated the agreement between the total
questionnaire score obtained in person (DN4) and by telephone (DN4i). Considering
the statistically significant data, the interpretation of the magnitude of the correlation
coefficient occurred as follows: strong (r ≥ 0.6), moderate (r ≤ 0.59), and weak (r
≤ 0.29).[10]
The weighted kappa statistic determined the agreement between individual questionnaire
items. The interpretation of kappa occurred as follows: excellent (> 0.80), substantial
(> 0.60), moderate (0.40-0.60), and fair to poor (< 0.40).[11] The SPSS 17.0 statistical software for Windows performed all analyses using a 5%
significance level.
Results
In total, 71 participants were eligible for the study. The final sample had 53 participants
with analyzable data, of which 50 (94.3%) presented the same results in DN4 and DN4i
for neuropathic pain screening. [Fig. 1] shows the sample layout.
Fig. 1 Sample recruitment according to eligibility criteria.
[Table 1] shows the sociodemographic and clinical characteristics of the participants with
analyzable data. Considering the Numerical Verbal Pain Scale, ranging from 0 to 10,
26.4% of the participants reported values between 2 and 8, of which half (13.2%) had
a positive score on DN4i.
Table 1
|
With neuropathic pain (n = 12)
|
Without neuropathic pain (n = 41)
|
|
Female gender (n, %)
|
33 (62.3)
|
|
Mean age (±SD)
|
55.5 (± 17.7)
|
|
Mean BMI (±SD)
|
27.95 (±5.52)
|
|
Comorbidities (n, %)
|
33 (62.3)
|
|
Diabetes
|
11 (33.3)
|
|
Marital status (n, %)
|
|
|
Single
|
21 (39.6)
|
|
Married
|
18 (34.0)
|
|
Widowed
|
10 (18.9)
|
|
Divorced
|
1 (1.9)
|
|
Not informed
|
3 (5.7)
|
|
Fracture site (n, %)
|
|
|
Ankle
|
23 (43.4)
|
|
Radius
|
19 (35.8)
|
|
Proximal femur
|
11 (20.8)
|
|
Trauma mechanism (n, %)
|
|
|
Fall from own height
|
23 (43.4)
|
|
Sprain
|
16 (30.2)
|
|
Fall from height
|
7 (13.2)
|
|
Traffic accident
|
6 (11.3)
|
|
Aggression
|
1 (1.9)
|
|
Numerical Verbal Pain Scale (n, %)
|
|
|
Presence of pain
|
14 (26.4%)
|
|
Positive DN4i score
|
7 (13.2%)
|
The orthopedists administering DN4 in person obtained 13 positive (sum ≥ 4) and 40
negative scores, while the two researchers who made the telephone calls got 12 positive
(sum ≥ 3) and 41 negative results. [Table 2] compares the percentages of positive scores for DN4 and DN4i items.
Table 2
|
In-person interview (DN4)
|
n (%)
|
|
Burning
|
15 (28.3)
|
|
Painful cold sensation
|
5 (9.4)
|
|
Electric shock
|
9 (16.9)
|
|
Tingling
|
14 (26.4)
|
|
Pins and needles
|
12 (22.6)
|
|
Numbness
|
10 (18.9)
|
|
Itching
|
6 (11.3)
|
|
Hypoesthesia to touch
|
8 (15.1)
|
|
hypoesthesia to needle prick
|
4 (7.5)
|
|
Brushing
|
10 (18.9)
|
|
Telephone interview (DN4i)
|
|
|
Burning
|
9 (16.9)
|
|
Painful cold sensation
|
8 (15.1)
|
|
Electric shock
|
8 (15.1)
|
|
Tingling
|
15 (28.3)
|
|
Pins and needles
|
8 (15.1)
|
|
Numbness
|
11 (20.8)
|
|
Itching
|
6 (11.3)
|
Pearson's correlation coefficient for agreement between the total questionnaire score
was r = 0.84 (p < 0.001), deemed strong considering its magnitude. Regarding the agreement
between the individual items of the questionnaires, the kappa coefficient was r = 0.84
(p < 0.001), which is excellent.
Discussion
Seven of the 12 positive DN4i scores were from females, including four subjects with
diabetes mellitus. This finding reinforces the factors associated with the development
of neuropathic pain, such as female gender and diabetes mellitus as an associated
comorbidity.[2]
[12]
[13]
The most predominant fracture site was the ankle (n = 23), and 17.4% of the affected
subjects had a positive score on DN4i. Rbia et al.[14] reinforce this finding, identifying the prevalence of neuropathic pain after ankle
fracture surgery in 23% of 271 patients, impacting their quality of life.
Attal et al.[15] suggested doctors and healthcare professionals should use DN4i for fast neuropathic
pain screening. A previous study from Bouhassira et al.[9] suggested the potential DN4i use in telephone surveys due to the significant discriminating
properties of the seven items. This observation was based on the fact that DN4i's
sensitivity (78%) and specificity (81.2%) are slightly lower than DN4 (82.9% and 89.9%,
respectively).[9]
[16] However, VanDenKerkhof et al.[17] point out that test sensitivity may vary according to the clinical condition. These
authors cited, for instance, a 92.5% sensitivity for central pain, while Aho et al.[18] reported a 66.2% sensitivity for peripheral nerve injury after a surgical procedure.
Despite the suggestion of telephone use of DN4i by Bouhassira et al.,[9] few studies in the literature have analyzed it. One of them[16] validated the method during a complementary telephone survey, which had no reference,
to determine the prevalence of chronic pain with neuropathic pain symptoms in a random
populational sample from Alberta, Canada. Research participants received the call
a week after the in-person application of DN4, which favors memory bias, as the patients
could remember their answers and repeat them. Furthermore, the call was from the same
doctor who applied DN4, compromising the internal and external validity of the study.
In our study, different staff members performed the in-person application of the DN4
and the telephone interview using DN4i; however, these professionals had the same
training, and the longer interval (4 to 6 months) could control the memory bias.
Keene et al.[19] corroborated that the use of the DN4i questionnaire via telephone months after DN4
application did not reduce the sensitivity for neuropathic pain screening in their
multicenter study to identify the prevalence of neuropathic pain after lower limb
fracture surgery through the application of DN4 in the third and sixth months. As
a result, they observed that 10% of patients without neuropathic pain 3 months after
surgery had pain at 6 months, which differs from the expectation that the intensity
and character of pain improve with the time after the injury.[19]
This study has some limitations, such as the difficulty in contacting patients who
underwent surgery longer ago, which limited the number of participants. As it includes
femur fractures, mortality bias in post-osteosynthesis surgical treatment must be
considered since the mortality rate after 1 year of treatment is significant. Another
critical point is the cognitive bias in older patients, as we did not apply specific
instruments for cognitive screening over the telephone.
Our study also has strengths, as the practicality of the connection avoids unnecessary
contact and facilitates the recruitment of the general population for epidemiological
studies with no impact of social distancing situations such as the COVID-19 pandemic.
The telephone use of DN4i also allows studies comparing clinical outcomes in different
regions.
Future studies are potentially required to investigate whether telephone DN4i predicts
treatment response since subjects with higher scores may be more responsive. It is
also relevant to develop epidemiological studies to better detail these data in the
literature, considering the greater practicality of telephone interviews. Research
in hospitals analyzing the number of operated patients who developed neuropathic pain
is also plausible for adjustments in given therapeutic approaches and management.
Conclusion
The application of the DN4i questionnaire by telephone compared to the in-person application
of the DN4 questionnaire shows strong agreement between individual items of the tools
and the total score obtained.
