Use of the painDETECT tool in rheumatoid arthritis suggests neuropathic and sensitization components in pain reporting

Figures & data

Table 1 Stratification of patients based on pain questionnaires and disease activity indices

Scoring system	Range	Interpretation
Visual analog scale	0–30	Mild pain
	31–53	Moderate pain
	54–100	Severe pain
painDETECT	≤12	Unlikely neuropathic pain
	13–18	Possible neuropathic pain
	≥19	Likely neuropathic pain
Disease Activity Score in 28 Joints	≤3.2	Low disease activity
	3.3–5.1	Moderate disease activity
	>5.1	High disease activity

Figure 1 (A) Table showing categorization of rheumatoid arthritis group by pain stratification using visual analog scale (VAS) and painDETECT questionnaires. The numbers (N) represent number of participants in the study with the scoring for unlikely neuropathic pain (UNP), possible neuropathic pain (PNP), and likely neuropathic pain (LNP), respectively. (B) Scatter graph showing relationship between VAS (mm) and painDETECT for the rheumatoid arthritis group. The R² value shows a positive correlation between VAS and painDETECT.

Table 2 Demographic characteristics for participants with rheumatoid arthritis and their use of disease-modifying drugsa

	All (N=100)	VAS			P-value
		Mild pain (N=19)	Moderate pain (N=27)	Severe pain (N=54)
DMARDs					0.093 χ^2
Methotrexate	82	10	22	50
Sulfasalazine	31	9	8	14
Hydroxychloroquine	38	8	15	15
Penicillamine	8	0	2	6
Ciclosporin	13	0	3	10
Biologics					0.043 χ^2
Infliximab	20	0	1	19
Abatacept	17	1	7	9
Tocilizumab	2	0	0	2
Pain medication					0.393 χ^2
Paracetamol	79	14	20	45
Ibuprofen	26	4	9	13
Other	48	9	7	32
painDETECT	8.77±5.58	2.84±1.30	5.00±1.96	12.74±4.46	<0.0001 F
DAS28	2.09±0.96	1.95±1.08	2.16±0.86	2.16±0.86

Notes:

a Continuous data are presented as M ± SD and categorical data are presented as n (%). One-way ANOVA (F) was used to determine the significant difference between the three groups (mild, moderate, and severe pain) for the parametric data. Categorical data were analysed using the chi-square test (χ²). painDETECT one-way ANOVA: (F[2, 97]=349.6, P<0.0001). The post hoc comparison for painDETECT using the Tukey test indicated that the significant difference is between all the conditions: mild vs moderate (M =−32.83, SD =1.947), mild vs severe (M =−60.54, SD =2.312), and moderate vs severe (M =−27.71, SD =2.099).

Abbreviations: VAS, visual analog scale; DMARDs, disease-modifying antirheumatic drugs; DAS28, Disease Activity Score in 28 Joints; M, mean; SD, standard deviation; ANOVA, analysis of variance.

Table 3 Characteristics for age, body mass index, sex, smoking history, and duration of diagnosis for rheumatoid arthritis study groupa

	All (N=100)	VAS			P-value
		Mild pain (N=19)	Moderate pain (N=27)	Severe pain (N=54)
Age, years					0.358 χ^2
≤30	7	1	3	3
31–40	15	5	4	6
41–50	52	12	12	28
51–60	20	1	7	12
61–70	6	0	1	5
BMI	24.31±2.31	23.45±1.31	23.78±1.68	24.88±2.69	0.0231 F
Sex					0.833 χ^2
Male	32	7	9	16
Female	68	12	18	38
Smoking history
Yes	10	1	1	8	0.253 χ^2
No	90	18	26	46	0.858 χ^2
Duration of RA					0.977 χ^2
2–4 years	16	3	4	9
≥5 years	84	16	23	45

Notes:

a Continuous data are presented as M ± SD and categorical data are presented as n (%). One-way ANOVA was used to determine the significant difference between the three groups (mild, moderate, and severe pain) for the parametric data. Categorical data were analyzed using the chi-square test (χ²). BMI one-way ANOVA: (F[2, 97]=3.919, P=0.0231). The post hoc comparison for the BMI using the Tukey test indicated that the statistical difference is between the mild and the severe (M =−1.432, SD =0.5981). However, there was no statistical difference between mild vs moderate (M =−0.3267, SD =0.6715) and between moderate vs severe (M =−1.106, SD =0.5285).

Abbreviations: VAS, visual analog scale; BMI, body mass index; RA, rheumatoid arthritis; M, mean; SD, standard deviation; ANOVA, analysis of variance.

Figure 2 (A) Box plot graph of the distribution of the mean visual analog scale (VAS) according to sex. (B) Box and whiskers plot of the distribution of the mean VAS with respect to present pain at the time of questioning compared with worst pain experienced (*P<0.05).

Figure 3 (A) Table showing categorization of rheumatoid arthritis group by body mass index (BMI). (B) Bar graph showing the distribution of visual analog scale (VAS) by BMI in the rheumatoid arthritis group. Participants were subgrouped by BMI into normal, overweight, and obese. The number (N) of participants within each BMI category is given. The mean (standard deviation [SD]) VAS in the groupings described is shown. There were statistically significant differences observed in the overweight and obese groups compared with controls (**P<0.01, ****P<0.0001).

Figure 4 (A) Bar graph showing mean ± standard deviation pain scores for visual analog scale (VAS) and their relationship to use of disease-modifying antirheumatic drug (DMARD) therapy in the rheumatoid arthritis group (**P≤0.01; ***P≤0.001; ****P≤0.0001). (B) Bar graph showing the relationship between the mean ± standard deviation VAS and painDETECT questionnaire. Participants were grouped into three: unlikely neuropathic pain (UNP), possible neuropathic pain (PNP), and likely neuropathic pain (LNP) (**P≤0.01; ****P≤0.0001).