Background/Purpose: Chronic back pain and functional impairment are disease characteristics common to all patients (pts) with axial spondyloarthritis (SpA), regardless of the presence of radiographic sacroiliitis in ankylosing spondylitis (AS) or its absence in non-radiographic axial SpA (nr-axSpA). This analysis compares baseline disease characteristics of pts with nr-axSpA and AS in registries and randomized clinical trials (RCT) with adalimumab (ADA).

Methods: Registry data in this analysis include the German SpA Inception Cohort (GESPIC)¹ that compared pts with AS by modified New York criteria (divided into >5 yrs and ≤5 yrs) and nr-axSpA (≤5 yrs) meeting modified ESSG criteria and a prospective cohort of TNF-naïve SpA pts meeting ASAS criteria for axial SpA.² ADA RCT data were derived from the ATLAS study³ in AS pts, and the ABILITY-1⁴ and Haibel⁵ studies in nr-axSpA pts. Pts in RCTs were selected based on a pre-specified level of disease activity and inadequate response to non-steroidal anti-inflammatory drugs.

Results: Mean age was similar in nr-axSpA and AS pts, ranging from 36-42 yrs (table). A higher proportion of AS pts had elevated CRP as compared to nr-axSpA pts and gender differences were observed, with nr-axSpA pts being predominantly female and AS pts primarily male. Symptomatic pts with nr-axSpA and AS often went undiagnosed for years. Similar levels of disease activity as measured by the BASDAI, pain scores, and pt and physician global assessments of disease activity were seen between nr-axSpA and AS pts in registries and RCTs, with levels of disease activity generally higher in RCT pts due to minimum levels of baseline disease activity required for study eligibility.

Conclusion: Registry and clinical trial data demonstrate that both nr-axSpA and AS patients have comparable burden of disease. These findings suggest that all patients with axial spondyloarthritis can present with similar debilitating signs and symptoms requiring treatment regardless of the extent of radiographic damage.

Table. nr-axSpA and AS baseline disease characteristics
	Registries					RCTs
	GESPIC			Kiltz		ATLAS	ABILITY-1	Haibel
	All AS	AS ≤5 yrs	nr-axSpA ≤5 yrs	AS	nr-axSpA	AS	nr-axSpA	nr-axSpA
	N=236	N=119	N=226	N=56	N=44	N=315	N=185	N=46
Age, yrs	35.6	36.1	36.1	41.2	39.1	42.2	38.0	37.5
Female, %	36.0	34.5	57.1	23.2	68.2	25.1	54.6	54.3
HLA-B27 +, %	88.2	73.1	74.7	89.1	86.4	78.7	75.1	67.4
Symptom duration, yrs	5.2	3.0	2.6	12.8	9.4	–	10.1	7.5
Duration since diagnosis, yrs	2.8	1.7	1.7	7.5	5.0	10.6	2.9	–
BASDAI, 0–10	4.0	4.0	3.9	4.2	3.6	6.3	6.5	6.3
Abnormal CRP, %	51.9	49.6	29.8	69.1	29.5	67.6	35.7	37.8
Total back pain, VAS 0–10	–	–	–	–	–	6.5	6.9	–
Total pain, VAS 0–10	5.0	4.8	4.8	4.7	4.0	–	6.8	7.2
PtGA of disease activity, VAS 0–10	5.0	5.0	4.9	4.6	4.0	6.3	6.8	6.6
PhGA of disease activity, VAS 0–10	4.5	4.4	3.6	3.5	2.7	5.7	5.7	5.9
Values are the mean unless otherwise indicated. AS, ankylosing spondylitis; BASDAI, Bath AS Disease Activity Index; CRP, C-reactive protein; nr-axSpA, non-radiographic axial spondyloarthritis; PhGA, physician global assessment; PtGA, patient global assessment; RCT, randomized clinical trial; VAS, visual analog scale.

References

1. Arthritis Rheum2009;60:717.

2. Arthritis Care Res2012. doi:10.1002/ACR.21688.

3. Arthritis Rheum2006;54:2136.

4. Abstract 2486A. Arthritis Rheum2011;63(Suppl):S970.

5. Arthritis Rheum 2008;58:1981.

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