Physical Function and Spinal Mobility Remain Stable Despite Radiographic Spinal Progression in Patients with Ankylosing Spondylitis Treated with TNF-α Inhibitors for Up to 10 Years

Denis Poddubnyy; Aleksandra Fedorova; Joachim Listing; Hildrun Haibel; Xenofon Baraliakos; Jürgen Braun; Joachim Sieper

doi:10.3899/jrheum.160594

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Figure 1.
Courses of radiographic spinal progression (mSASSS), disease activity (BASDAI), functional status (BASFI), and spinal mobility (BASMI) in patients who completed (A) 4, (B) 6, (C) 8, and (D) 10 years of anti-TNF treatment. Patients were included only if clinical and radiographic data were all available at all timepoints shown. * Week 12 was considered as baseline for BASDAI, BASFI, and BASMI to exclude initial improvement related to initiation of anti-TNF therapy. mSASSS: modified Stoke Ankylosing Spondylitis Spine Score; BASDAI: Bath Ankylosing Spondylitis Disease Activity Index; BASFI: Bath Ankylosing Spondylitis Functional Index; BASMI: Bath Ankylosing Spondylitis Metrology Index; anti-TNF: antitumor necrosis factor.
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Figure 2.
Cumulative probability plots of (A) BASFI and (B) BASMI changes in relation to radiographic spinal progression (mSASSS change) over up to 10 years of anti-TNF treatment. Change values between the followup timepoint and baseline for mSASSS, and between the followup timepoint and Week 12 for BASFI and BASMI are shown. BASFI: Bath Ankylosing Spondylitis Functional Index; BASMI: Bath Ankylosing Spondylitis Metrology Index; mSASSS: modified Stoke Ankylosing Spondylitis Spine Score; anti-TNF: antitumor necrosis factor.
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Figure 3.
Adjusted mean changes (least square means) of (A) BASFI and (B) BASMI in relation to radiographic spinal progression (mSASSS change) and changes in disease activity (BASDAI change). BASFI: Bath Ankylosing Spondylitis Functional Index; BASMI: Bath Ankylosing Spondylitis Metrology Index; mSASSS: modified Stoke Ankylosing Spondylitis Spine Score; BASDAI: Bath Ankylosing Spondylitis Disease Activity Index.

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Table 1.

Baseline and Week 12^* characteristics of the included patients. Values are mean ± SD unless otherwise specified.

Characteristics	Infliximab		Etanercept		All
Patients, n	43		17		60
Male, n (%)	29 (67)		15 (88)		44 (73)
Age, yrs	38.0 ± 7.7		36.0 ± 6.6		37.5 ± 7.4
Disease duration, yrs	14.0 ± 8.6		13.1 ± 7.5		13.8 ± 8.3
HLA-B27–positive, n (%)	37 (88)		14 (82)		51(85)
mSASSS	11.2 ± 16.4		10.9 ± 15.5		11.1 ± 16.1
	Baseline	Week 12	Baseline	Week 12	Baseline	Week 12
BASDAI	6.3 ± 1.4	3.0 ± 1.7	6.5 ± 1.2	2.6 ± 2.2	6.4 ± 1.3	2.9 ± 1.8
BASFI	5.2 ± 1.9	3.1 ± 1.9	5.3 ± 1.9	2.9 ± 2.6	5.2 ± 1.9	3.1 ± 2.1
BASMI	3.4 ± 2.1	2.7 ± 1.9	3.9 ± 2.0	2.1 ± 2.0	3.5 ± 2.0	2.5 ± 1.9
CRP, mg/l	23.7 ± 18.2	4.8 ± 3.0	23.0 ± 19.3	5.9 ± 2.4	23.5 ± 18.3	5.1 ± 2.8

↵* Week 12 data were used for clinical variables as baseline in the longitudinal analysis to eliminate the initial effect of TNF blockers. mSASSS: modified Stoke Ankylosing Spondylitis Spine Score; BASDAI: Bath Ankylosing Spondylitis Disease Activity Index; BASFI: Bath Ankylosing Spondylitis Functional Index; BASMI: Bath Ankylosing Spondylitis Metrology Index; CRP: C-reactive protein.

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Table 2.

Status scores for the mSASSS, BASDAI, BASFI, and BASMI in patients who completed a 2-, 4-, 6-, 8-, and 10-year followup. Values are mean ± SD unless otherwise specified.

Variables^*	Baseline/week 12	Yr 2	Yr 4	Yr 6	Yr 8	Yr 10
n	60	57	41	34	23	17
mSASSS	11.1 ± 16.1	12.9 ± 17.2	12.0 ± 2.3	14.6 ± 17.1	16.0 ± 17.5	17.2 ± 17.7
BASDAI	2.9 ± 1.8	2.4 ± 2.0	2.3 ± 1.6	2.3 ± 1.6	2.3 ± 1.7	2.0 ± 1.3
BASFI	3.1 ± 2.1	2.8 ± 2.4	2.8 ± 2.2	2.9 ± 2.3	3.0 ± 2.5	2.4 ± 1.4
BASMI	2.5 ± 1.9	2.4 ± 2.1	2.1 ± 2.0	2.2 ± 2.1	2.5 ± 2.1	2.6 ± 1.7

↵* Week 12 data were used as baseline for clinical variables BASDAI, BASFI, and BASMI. mSASSS: modified Stoke Ankylosing Spondylitis Spine Score; BASDAI: Bath Ankylosing Spondylitis Disease Activity Index; BASFI: Bath Ankylosing Spondylitis Functional Index; BASMI: Bath Ankylosing Spondylitis Metrology Index.

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Table 3.

Variable estimates from the generalized linear mixed effect model analysis of the effect of radiographic spinal progression (mSASSS) and disease activity change (BASDAI) on the change in the functional status (BASFI) and spinal mobility (BASMI) during longterm treatment with TNF inhibitors.

Independent Variables	Outcome (Dependent Variable)
	BASFI Change from Baseline (Week 12)		BASMI Change from Baseline (Week 12)
	β (95% CI)	p	β (95% CI)	p
mSASSS change from baseline	0.0 (−0.03 to 0.03)	0.89	0.05 (0.01–0.09)	0.022
BASDAI change from baseline (Week 12)	0.64 (0.54–0.73)	< 0.001	0.14 (0.01–0.26)	0.035

mSASSS: modified Stoke Ankylosing Spondylitis Spine Score; BASDAI: Bath Ankylosing Spondylitis Disease Activity Index; BASFI: Bath Ankylosing Spondylitis Functional Index; BASMI: Bath Ankylosing Spondylitis Metrology Index; TNF: tumor necrosis factor.