Background/Purpose: The ASAS criteria for peripheral spondyloarthritis (SpA) allow for classification of patients with SpA who present with peripheral arthritis, enthesitis and/or dactylitis.¹ ABILITY-2, a placebo-controlled trial of adalimumab (ADA) for the treatment of peripheral SpA in patients not previously diagnosed with psoriasis or psoriatic arthritis (PsA), is the first pivotal study to use the ASAS criteria to classify patients for study entry. This analysis characterizes ABILITY-2 patients based on gender and the pattern of joint involvement – oligoarticular vs. polyarticular.

Methods: ABILITY-2 is an ongoing, randomized, controlled multicenter phase 3 study. Eligible patients were age ≥18 yrs, fulfilled ASAS peripheral SpA criteria, did not have a diagnosis of psoriasis, PsA, or ankylosing spondylitis, and had inadequate response or intolerance to NSAIDs. Required baseline disease activity at study entry included patient global assessment of disease activity (PGA) and of pain (PGA-pain) ≥40mm (0–100 mm VAS), ≥2 SJC and TJC, ≥2 digits with dactylitis or enthesitis accompanied by at least 1 joint with active arthritis, or ≥2 sites with enthesitis judged to be severe by the investigator.  Subgroup analyses of baseline demographics and disease activity were conducted by gender and by pattern of joint involvement (oligoarticular 2–4 vs. polyarticular >4 joints which are either tender and/or swollen).

Results: Of the 165 patients randomized, 90 (54.5%) were female and 125 (75.8%) had polyarticular disease. Females were slightly older and had a lower proportion with HLA-B27 positivity, but overall, had similar disease activity parameters as males (table). Predominantly lower limb involvement was observed at baseline in 57% of males, 50% of females, 59% of patients with oligoarticular disease, and 51% of patients with polyarticular disease. More patients with polyarthritis were HLA-B27+ compared to those with oligoarthritis (table). Although fewer polyarticular patients had an abnormal hs-CRP at baseline, the mean hs-CRP and the proportion of patients with accompanying enthesitis and dactylitis were greater in those with polyarticular disease. Otherwise, both patient and physician global assessments, BASDAI, HAQ-S and the physical component score of the SF-36v2 were similar between these 2 subgroups.

 Conclusion: In non-PsA peripheral SpA patients with inadequate response or intolerance to NSAIDs, similar levels of disease activity as measured by patient and physician global assessments were observed regardless of extent of joint involvement. Likewise, functional impairment was also comparable between patients with oligo- and polyarticular joint disease.

 

Table. Baseline demographics and disease characteristics in subgroups of peripheral SpA patients based on gender and pattern of joint involvement
Randomized Patients N=165	Gender		Pattern of Joint  Involvement
	Male n = 75	Female n = 90	Oligoarticular n = 34	Polyarticular n = 125
Demographics
Age, years	38.5	42.3	39.6	41.2
Female, %	–	–	55.9	55.2
SpA symptom durationa, years	6.62	7.67	6.65	7.45
HLA-B27+, %	65.3	58.4	52.9	62.1
Disease Activity
hs-CRP, mg/L	11.2	9.4	8.3	11.0
hs-CRP abnormal, %	46.7	41.1	52.9	42.4
TJC, 0–78	10.77	15.38	3.00	16.69
SJC, 0–76	6.21	7.11	2.12	8.24
MASES, 0–13	2.51	4.07	1.44	3.89
MASES >0, %	73.3	75.6	52.9	80.0
Leeds enthesitis index, 0–6	1.29	1.59	0.56	1.73
Leeds >0, %	65.3	60.0	44.1	68.0
SPARCC enthesitis index, 0–16	3.53	4.28	1.91	4.54
SPARCC >0, %	81.3	75.6	64.7	81.6
Dactylitis count	0.41	0.57	0.12	0.63
Dactylitis >0, %	20.0	24.7	8.8	27.4
PGA, 0–100 mm	63.71	67.59	63.97	66.50
PGA-pain, 0–100 mm	62.45	67.01	62.47	65.70
PhGA, 0–100 mm	59.29	58.18	56.12	59.72
BASDAI, 0–10	5.21	5.97	5.37	5.72
SF-36v2 PCS	35.65	33.58	36.77	33.88
HAQ-S	0.83	1.11	0.88	1.02
Values are the mean unless otherwise indicated. aN=73, 88, 34, 121, respectively. BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; HAQ-S, Health Assessment Questionnaire modified for Spondyloarthropathies; hs-CRP, high-sensitivity C-reactive protein; MASES, Maastricht Ankylosing Spondylitis Enthesitis Score; PGA, Patient’s Global Assessment of disease activity; PGA-pain, Patient’s Global Assessment of pain; PhGA, Physician’s Global Assessment; SF-36v2 PCS, Short Form-36 Health Status Survey version 2 physical component summary; SJC, swollen joint count; SpA, spondyloarthritis; SPARCC, Spondyloarthritis Research Consortium of Canada; TJC, tender joint count

References

1. Ann Rheum Dis 2011;70:25–31.

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