Table 1 Combined and separate characteristics of 55 axSpA patients on adalimumab (n = 34) or etanercept (n = 21) with TNFi serum trough level measurements

Demographics

 Age (years)

45 ± 12

45 ± 13

46 ± 12

 Sex (male)

26 (47)

14 (41)

12 (57)

 BMI (kg/m²)

26.4 (23.9–32.5)

27.7 (24.6–33.7)

24.3 (22.2–29.7)*

 BMI (kg/m²)

   < 25

21 (38)

9 (27)

12 (57)*

  25–30

15 (27)

10 (29)

5 (24)

   ≥ 30

19 (35)

15 (44)

4 (19)

Disease status

 Diagnosis of AS

46 (84)

25 (74)

21 (100)**

 Duration of symptoms (years)

21 ± 12

21 ± 14

20 ± 8

 HLA-B27 positive

45 (82)

27 (79)

18 (86)

 History of EAM

  IBD

5 (9)

5 (15)

0 (0)

  Psoriasis

7 (13)

5 (15)

2 (10)

  Uveitis

12 (22)

8 (24)

4 (19)

 ASDAS CRP

2.0 (1.5–3.0)

2.3 (1.7–3.1)

1.6 (1.3–2.0)**

  ASDAS ≥ 2.1

25 (46)

21 (64)

4 (19)**

 BASDAI (0–10)

3.2 (2.0–5.5)

4.4 (2.8–6.2)

2.6 (1.3–3.5)*

  BASDAI ≥ 4.0

21 (39)

17 (52)

4 (19)*

 CRP (mg/L)

3.0 (2.0–6.5)

3.9 (2.0–6.1)

2.0 (2.0–6.6)

  CRP ≥ 5.0

23 (42)

15 (44)

8 (38)

Therapy

 Current NSAID use

18 (33)

12 (36)

6 (29)

 Current DMARD use

4 (7)

2 (6)

2 (10)

 Previous TNFi

12 (22)

11 (32)

1 (5)*

 Treatment duration current TNFi (months)

41 (10–68)

27 (7–57)

60 (18–80)*

 Treatment duration since first TNFi (months)

49 (14–87)

41 (14–91)

60 (18–90)

 TNFi dosage

  Standard dosage

46 (84)

29 (85)

17 (81)

  Higher dosage

2 (4)

2 (6)

0 (0)

  Lower dosage

7 (13)

3 (9)

4 (19)

 Serum trough level (μg/ml)

NA

5.2 (3.7–8.0)

1.6 (1.1–2.4)