Page 83 - Recognizing axial spondyloarthritis - Janneke de Winter

ANTI-CD74 ANTIBODIES IN EARLY AXIAL SPA
(n=172) versus those not fulfilling either rheumatologist diagnosis or ASAS criteria (n=238) and (2) patients in the SPACE cohort with confirmed diagnosis of axSpA (n=143) or no axSpA (n=64) after 1 of year follow up (1 year follow-up data were available in 244 patients in total). As shown in Table 2, the results of these additional analyses were comparable to the primary analyses.
Anti-CD74 IgA antibodies in axSpA subpopulations
We additionally explored if anti-CD74 IgA antibodies were associated with a specific sub-population of axSpA patients. In the exploratory cohort, the mean disease duration of AS patients with or without anti-CD74 IgA antibodies did not differ (24.12 vs. 24.35 months respectively, p=.931).
In the SPACE cohort, on comparison of axSpA patients with or without HLA-B27, elevated CRP, inflammatory back pain, sacroiliitis shown on MRI and peripheral (enthesitis, arthritis or dactylitis) or extra-articular (psoriasis, uveitis or IBD) manifestations there were no differences (data not shown). AxSpA patients with radiographic sacroiliitis more often had anti-CD74 IgA antibodies than axSpA patients without radiographic sacroiliitis (66.7% vs. 46.4%, p=0.031).
In regression analysis within the population of axSpA patients, sacroiliitis on MRI and heel enthesitis were both significantly associated with elevated anti-CD74 IgA levels (odds ratio (OR)=2.50, p=.005 and OR=2.56, p=.002, respectively). HLA-B27, CRP, inflammatory back pain, radiographic sacroiliitis and peripheral manifestations other than heel enthesitis or extra-articular manifestations were not associated with anti-CD74 IgA levels.
Table 1. Demographic and disease characteristics of axSpA patients and chronic back pain (CBP) patients of the SPACE cohort.
Diagnosed with axSpA
Yes (n=274)
119 (43.4) 30.7 (7.9) 165 (60.7) 131 (47.8) 13.1 (7.0)
213 (77.7) 59 (21.6)
No (n=286)
181 (28.3) 31.4 (8.5) 63 (22.1) 111 (38.8) 13.5 (7.2)
154 (54.0) 23 (8.1)
Male (n, %)
Age (mean, SD)
HLA-B27 positive (n, %) Positive family history (n, %) Duration of back pain in months (mean, SD)
Inflammatory back pain (n, %) Peripheral arthritis (n, %)
P-value
<0.001 0.83 <0.001 0.03 0.59
<0.001 <0.001
Table 1 continues
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