Among 105 patients enrolled, a total of 88 patients were included in the analyses. Seventeen patients were excluded due to the incomplete medical data. Among 88 patients included, 43 patients (48.9%) showed low disease activity (DAS28-6month ≤3.2). The mean age of all patients was 44 ± 13 years (range, 20–78), and 81.8% were females. Baseline characteristics of patients were not statistically different between the two groups, except for hypertension, which was more prevalent in patients with moderate-to-high disease activity (p = 0.039). The most prevalent comorbidity was hypertension (15.9%) followed by osteoporosis and hyperlipidemia (both 11.3%). Both RF and ACPA were not associated with treatment response. Methotrexate was the most common concomitant drug prescribed (87.5%), followed by hydroxychloroquine (54.5%) and leflunomide (39.7%) (Table 1).
Table 1. Patient characteristics according to the disease activity at 6 months treatment of TNF inhibitors
Characteristics, n (%)
|
Low disease activity
|
Moderate to high disease activity
|
p-value
|
Sex
|
|
|
0.100
|
|
Male
|
11 (25.6)
|
5 (11.1)
|
|
|
Female
|
32 (74.4)
|
40 (88.9)
|
|
Age, years
|
50.7 ± 13.1
|
55.0 ± 14.0
|
0.137
|
|
< 65
|
36 (83.7)
|
34 (75.6)
|
0.431
|
|
≥ 65
|
7 (16.3)
|
11 (24.4)
|
|
BMI, kg/m2
|
23.1 ± 3.3
|
22.4 ± 3.9
|
0.342
|
Duration of rheumatoid arthritis, years
|
8.2 ± 5.5
|
10.0 ± 6.9
|
0.171
|
Alcohol
|
|
|
0.155
|
|
Yes
|
7 (16.3)
|
4 (8.9)
|
|
|
No
|
34 (79.1)
|
41 (91.1)
|
|
Smoking
|
|
|
0.949
|
|
Current
|
5 (11.6)
|
5 (11.1)
|
|
|
Former
|
2 (4.7)
|
2 (4.4)
|
|
|
Never
|
35 (81.4)
|
38 (84.4)
|
|
Rheumatoid factor
|
|
|
0.328
|
|
Positive
|
30 (69.8)
|
35 (77.8)
|
|
|
Negative
|
13 (30.2)
|
9 (20.0)
|
|
ACPA
|
|
|
0.609
|
|
Positive
|
28 (71.8)
|
31 (75.6)
|
|
|
Negative
|
11 (28.2)
|
9 (22.0)
|
|
Concomitant drug
|
|
|
|
|
Hydroxychloroquine
|
|
|
0.834
|
|
|
Yes
|
24 (55.8)
|
24 (53.3)
|
|
|
|
No
|
19 (44.2)
|
21 (46.7)
|
|
|
Leflunomide
|
|
|
0.514
|
|
|
Yes
|
19 (44.2)
|
16 (35.6)
|
|
|
|
No
|
24 (55.8)
|
29 (64.4)
|
|
|
Methotrexate
|
|
|
0.522
|
|
|
Yes
|
39 (90.7)
|
38 (84.4)
|
|
|
|
No
|
4 (9.3)
|
7 (15.6)
|
|
|
Sulfasalazine
|
|
|
0.224
|
|
|
Yes
|
8 (18.6)
|
4 (8.9)
|
|
|
|
No
|
35 (81.4)
|
41 (91.1)
|
|
|
Tacrolimus
|
|
|
0.551
|
|
|
Yes
|
5 (11.6)
|
8 (17.8)
|
|
|
|
No
|
38 (88.4)
|
37 (82.2)
|
|
Comorbidity
|
|
|
|
|
Diabetes
|
|
|
0.677
|
|
|
Yes
|
2 (4.7)
|
4 (8.9)
|
|
|
|
No
|
41 (95.3)
|
41 (91.1)
|
|
|
Dyslipidemia
|
|
|
0.316
|
|
|
Yes
|
3 (7.0)
|
7 (15.6)
|
|
|
|
No
|
40 (93.0)
|
38 (84.4)
|
|
|
Hypertension
|
|
|
0.039
|
|
|
Yes
|
3 (7.0)
|
40 (93.0)
|
|
|
|
No
|
11 (24.4)
|
34 (75.6)
|
|
|
Osteoporosis
|
|
|
0.739
|
|
|
Yes
|
4 (9.3)
|
6 (13.3)
|
|
|
|
No
|
39 (90.7)
|
39 (86.7)
|
|
|
Vitamin D deficiency
|
|
|
1.000
|
|
|
Yes
|
3 (7.0)
|
4 (8.9)
|
|
|
|
No
|
40 (93.0)
|
41 (91.1)
|
|
ACPA: Anticyclic citrullinated peptide antibody; BMI: body mass index; DAS28: disease activity score 28 joints; ESR: erythrocyte sedimentation rate; CRP: C-reactive protein
To determine the possible influence of disease status of patients on their response to TNFi, baseline DAS28 and its subcomponents were examined. Baseline DAS28 was significantly lower in the low disease activity group than in the moderate-to-high disease activity group (p = 0.034) (Table 2).
Table 2. Baseline DAS28 and its subcomponents according to the disease activity at 6 months treatment of TNF inhibitors
|
Low disease activity
|
Moderate to high disease activity
|
p-value
|
DAS28
|
5.5 ± 1.2
|
6.0 ± 1.1
|
0.034
|
Total joint count 28
|
9.1 ± 8.2
|
12.0 ± 7.1
|
0.077
|
Swollen joint count 28
|
6.8 ± 7.5
|
7.7 ± 5.1
|
0.499
|
Global health
|
58.6 ± 19.6
|
59.2 ± 17.1
|
0.875
|
ESR
|
47.7 ± 28.7
|
53.0 ± 27.0
|
0.371
|
CRP
|
2.5 ± 3.9
|
2.1 ± 2.1
|
0.484
|
DAS28: disease activity score 28 joints; ESR: erythrocyte sedimentation rate; CRP: C-reactive protein; count
Among the 14 SNPs genotyped, GG-carriers of rs1862513 were more likely to show low disease activity at 6-months of TNFi treatment than GC or CC-carriers (p = 0.020). Marginal significance was revealed for Rs3397, with higher disease activity in CC-carriers than in patients with the T allele (p = 0.059). Other 12 SNPs did not reach statistical significance in terms of DAS28-6month (Table 3).
Table 3. Genotype association with the disease activity at 6 months treatment of TNF inhibitors
Gene, rs number
|
Low disease activity
|
Moderate to high disease activity
|
p-value
|
RETN rs1862513
|
|
|
0.020
|
|
GG
|
11 (25.6)
|
3 (6.7)
|
|
|
GC, CC
|
32 (74.4)
|
42 (93.3)
|
|
RETN rs3219175
|
|
|
0.673
|
|
AA
|
3 (7.0)
|
2 (4.4)
|
|
|
AG, GG
|
40 (93.0)
|
43 (95.6)
|
|
RETN rs3745367
|
|
|
0.391
|
|
GG
|
15 (34.9)
|
20 (44.4)
|
|
|
GA, AA
|
28 (65.1)
|
25 (55.6)
|
|
RETN rs7408174
|
|
|
1.000
|
|
CC
|
1 (2.3)
|
2 (4.4)
|
|
|
CT, TT
|
42 (97.7)
|
43 (95.6)
|
|
TNFAIP3 rs5029937
|
|
|
0.574
|
|
GG
|
37 (86.0)
|
36 (80.0)
|
|
|
GT
|
6 (14.0)
|
9 (20.0)
|
|
PDZD2 rs1532269
|
|
|
0.198
|
|
CC
|
14 (32.6)
|
21 (46.7)
|
|
|
CG, GG
|
29 (67.4)
|
24 (53.3)
|
|
MMEL1 rs3890745
|
|
|
0.654
|
|
TT
|
16 (37.2)
|
14 (31.1)
|
|
|
TC, CC
|
27 (62.8)
|
31 (68.9)
|
|
MMEL1 rs2843401
|
|
|
0.505
|
|
TT
|
13 (30.2)
|
17 (37.8)
|
|
|
TC, CC
|
30 (69.8)
|
28 (62.2)
|
|
TNFRSF1A rs767455
|
|
|
0.328
|
|
TT
|
30 (69.8)
|
36 (80.0)
|
|
|
TC, CC
|
13 (30.2)
|
9 (20.0)
|
|
TNFRSF1B rs3397
|
|
|
0.059
|
|
CC
|
16 (37.2)
|
26 (57.8)
|
|
|
CT, TT
|
27 (62.8)
|
19 (42.2)
|
|
CD226 rs763361
|
|
|
0.658
|
|
CC
|
17 (39.5)
|
15 (33.3)
|
|
|
CT, TT
|
26 (60.5)
|
30 (66.7)
|
|
AFF3 rs10865035
|
|
|
0.464
|
|
AA
|
9 (20.9)
|
13 (28.9)
|
|
|
AG, GG
|
34 (79.1)
|
32 (71.1)
|
|
PTPRC rs10919563
|
|
|
0.505
|
|
GG
|
30 (69.8)
|
28 (62.2)
|
|
|
GA,AA
|
13 (30.2)
|
17 (37.8)
|
|
Chr.17 rs2872507
|
|
|
0.831
|
|
GG
|
26 (60.5)
|
26 (57.8)
|
|
|
GA, AA
|
17 (39.5)
|
19 (42.2)
|
|
We performed multivariable logistic regression analysis to determine the independent factors including both genetic and non-genetic variables. Hypertension, baseline DAS28, rs1862513, and rs3397 (all p < 0.1 in univariate analysis), sex, age, and body mass index were also included. The model explained 24.5% (Nagelkerke R2) of the variance in DAS28-6month and correctly classified 67.0% of the cases. C-allele carriers of rs1862513 were 4.67-times more likely to exhibit moderate-to-high disease activity than GG carriers. CC carriers of rs3397 were 2.66-times more likely to exhibit moderate-to-high disease activity than T-allele carriers (Table 4).
Table 4: Multivariable binary logistic model for moderate to high disease activity at 6 months treatment of TNF inhibitors
|
OR (95% CI)
|
p-value
|
Adjusted OR* (95% CI)
|
p-value
|
Female
|
2.75 (0.87-8.73)
|
0.086
|
|
|
Age ≥ 65
|
1.66 (0.58-4.79)
|
0.345
|
|
|
BMI
|
0.94 (0.84-1.06)
|
0.339
|
|
|
Hypertension
|
4.31 (1.11-16.74)
|
0.035
|
3.65 (0.85-15.63)
|
0.082
|
Baseline DAS28
|
1.53 (1.02-2.29)
|
0.039
|
1.45 (0.94-2.23)
|
0.091
|
Rs1862513 CC, CG (reference = G G)
|
4.81 (1.24-18.69)
|
0.023
|
4.67 (1.14-19.19)
|
0.033
|
Rs3397 CC
(reference = CT, TT)
|
2.31 (0.98-5.43)
|
0.055
|
2.66 (1.04-6.82)
|
0.041
|
*Adjusted for sex, age, BMI, hypertension, baseline DAS28, rs1862513 and rs3397.
OR: odds ratio, CI: confidence interval, BMI: body mass index, DAS28: disease activity score 28
A calibration plot of the actual response to TNFi treatment versus probabilities of response estimated by the multivariable model was drawn with loess function to validate the regression model. The fitted loess lines indicated excellent calibration, and variability was minor within the range of predicted probability where the majority of patients were in (Figure 1).
To assess the predictive accuracy of TNFi response, a ROC curve based on the multivariable model was drawn. The area under the ROC curve for detecting the response to TNFi was 0.77 (95% CI, 0.67-0.87) (Figure 2).