Background/Purpose:

Peripheral spondyloarthritis (pSpA) is characterized by arthritis, enthesitis, and/or dactylitis. Enthesitis is considered a core outcome domain for SpA; however, there is no clear recommendation which of the available enthesitis tools should be used. The objective of this analysis was to evaluate the validity of different enthesitis indices in patients (pts) with non-psoriatic pSpA during treatment with adalimumab (ADA).

Methods:

ABILITY-2 is a multicenter phase 3 study. Eligible pts were age ≥18 yrs, fulfilled ASAS pSpA criteria, and had active disease. Pts were randomized to ADA 40 mg every other week (wk) or placebo (PBO) for 12 wks followed by 144 wks of open-label ADA. 29 enthesitis sites based on Leeds (range 0–6) and SPARCC (Spondyloarthritis Research Consortium of Canada, 0–16) enthesitis indices, and the MASES (Maastricht Ankylosing Spondylitis Enthesitis Score, 0–13) were assessed during the study. Discriminatory capacity and sensitivity to change of enthesitis indices at wk 12 were calculated: mean differences from BL to wk 12 in ADA vs PBO-treated pts with corresponding 95% confidence limits, standardized mean differences, and Guyatt’s effect sizes. Presence of enthesitis at each anatomical enthesitis site at BL and proportion of sites that show resolution or new onset enthesitis from BL to wk 12, ADA vs PBO, were analyzed.

Results:

165 pts (ADA 84/PBO 81) were randomized. At BL 143 (87%) had ≥1 enthesitis site. The Leeds and SPARCC enthesitis scores showed higher discriminatory ability and sensitivity to change compared to the MASES (Table). Individual enthesitis site analysis suggests that in the overall population the percent change from BL to wk 12 at the following sites may have higher discriminatory capacity to other more axial sites: Achilles tendon (ADA 52.8% vs PBO 13.5%), greater trochanter (42.6% vs 6.8%), lateral epicondyle humerus (63.9% vs 0%), and medial epicondyle humerus (51.2% vs 0%). Among enthesitis sites positive at BL, a greater proportion showed resolution at wk 12 among pts on ADA in the Achilles tendon (ADA 60.4% vs PBO 36.5%, P=0.019), medial epicondyle (73.2% vs 48.7%, P=0.038), and lateral epicondyle (80.6% vs 52.8%, P=0.023). Among sites negative at BL less new onset enthesitis was observed with ADA at the following sites: Achilles tendon (ADA 3.6% vs PBO 10.9%, P=0.041), lateral epicondyle (4.7% vs 15.1%, P=0.006), greater trochanter (3.4% vs 14.4%, P=0.005), quadriceps insertion patella (1.5% vs 7.0%, P=0.034), and medial condyle femoral (1.6% vs 9.2%, P=0.009). 

Table. Enthesitis Index Mean Change (±SD) [95% CL] from Baseline to Week 12, SMD, and Guyatt’s Effect Size*
	ADA	PBO	Mean Difference (ADA-PBO)	SMD	Guyatt’s Effect Size
Leeds	-1.35 (±1.20) [-1.69, -1.02] n=51	-0.45 (±1.27) [-0.81, -0.09] n=51	-0.90 [-1.39, -0.42]	0.73	-1.07
SPARCC	-2.35 (±2.46) [-2.97, -1.73] n=63	-1.00 (±2.37)  [-1.59, -0.41] n=65	-1.35 [-2.19, -0.51]	0.56	-0.99
MASES	-2.02 (±2.78) [-2.76, -1.28] n=57	-1.17 (±2.50) [-1.79, -0.55] n=65	-0.85 [-1.80, 0.10]	0.32	-0.81
*Among patients who had score ≥1 for that index. CL, confidence limit; MASES, Maastricht Ankylosing Spondylitis Enthesitis Score; SD, standard deviation; SMD, standardized mean difference; SPARCC, Spondyloarthritis Research Consortium of Canada.

Conclusion:

In ABILITY-2, the LEEDS and SPARCC enthesitis indices showed better discriminatory capacity and sensitivity to change compared to the MASES during treatment with ADA in pSpA patients. Enthesitis sites showing higher discriminatory capacity are peripheral sites predominantly in the Leeds and SPARCC indices which may explain their better performance compared to the MASES, which has fewer peripheral sites.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/better-performance-of-the-leeds-and-sparcc-enthesitis-indices-compared-to-the-mases-in-patients-with-peripheral-spondyloarthritis-during-treatment-with-adalimumab/