Background/Purpose:

New Axial Spondyloarthritis Classification Criteria  include an imaging arm and a clinical arm. The imaging arm includes radiographic ax-SpA patients who have radiographic sacroilitis according to modified New York criteria  and  non-radiographic (nr) ax-SpA patients who have sacroiliitis only by MRI. Although there is no doubt that radiographic and non-radiographic axSpA  have many overlapping features, it is now one of the hot topics of discussion  whether  they are different  entities.

The aim of this study was to compare the demographics and clinical characteristics between the radiographic and nr-axSpA patients fulfilling the criteria of the imaging arm.

Methods:

A local database has been used since December 2008 to register all patients fulfilling the imaging arm of AxSpA classification criteria. Data related to demographics, clinical features, disease activity, functional status, treatment were recorded.

Results:

720 patients who met the study criteria were identified. Radiographic sacroiliitis according to modified New York criteria was present in 533 patients. The remaining 187 patients were classified as nr-axSpA based on MRI findings. Demographics and clinical characteristics are summarized in Table 1. Patients with nr-axSpA had an earlier onset of symptoms and were more often females. Prevalence of extraspinal manifestations was similar in both groups, except for anterior uveitis, which was more frequently reported by the patients with radiographic axSpA. C-reactive protein levels were significantly higher in patients with radiographic sacroiliitis as compared to those with nr-AxSpA. HLA-B27 prevalence  was numerically greater among patients with radiographic axSpA , but was not  statistically significant. Disease activity measured by BASDAI, but not by ASDAS, was higher in the nr-axSpA group; BASFI scores were similar in both groups. BASMI score was higher in radiographic ax-SpA patients. While anti-TNF therapy was used more frequently by patients with radiographic sacroiliitis, DMARD use was similar in both groups.

Conclusion:

Although many demographic and clinical features are similar between the ax-SpA patients with and without radiographic sacroiliitis classified with the imaging arm, differences such as higher prevalence of females and numerically lower prevalence of HLA-B27 among patients with nr-axSpA are of interest.

Table 1. Demographics and clinical characteristics of the radiographic and non-radiographic axSpA patients.

Demographic and clinical features	Radiographic sacroiliitis (n:533)	Non-radiographic sacroiliitis (n:187)	P
Age, mean ± SD	43 ± 12.0	42 ± 13.2	0.232
Male sex n,%	395, 74.1	72, 38.5	<0.001
Age at beginning of the symptoms, mean ± SD	25 ± 9.1	28 ± 10.3	0.010
Diagnostic delay, mean ± SD	8 ± 8.5	7 ± 8.0	0.023
Arthritis n,(%)	195, (36.6)	42, (22.5)	0.491
Hip replacement n,(%)	23, (4.3)	0	0.023
Anterior uveitis n,%	97, (18.2)	10, (5.3)	0.007
Psoriasis n,%	16, (3.0)	4, (2.1)	0.399
IBD n,%	16, (3.0)	2, (1.0)	0.082
HLA B27 positivity n1/n2 (%)	166/243 (68.3)	46.3 % (36/78)	0.146
CRP mg/dl , mean ± SD	19.0 ± 25.6	9.5 ±17.1	<0.001
BASDAI, mean ± SD	3.5 ± 2.2	4.3 ± 2.5	<0.001
ASDAS-CRP, mean ± SD	2.9 ±1.1	2.1 ±1.1	0.223
BASFI, mean ± SD	2.9 ±2.6	2.7 ±2.5	0.346
BASMI, mean ± SD	3.9 ±1.9	2.3 ±1.0	<0.001
SSZ, n, (%)	132, (24.2)	21, (11.2)	0.316
MTX, n, (%)	34, (6.3)	4, (2.1)	0.317
Anti TNF , n,(%)	103, (19.3)	8, (4.2)	<0.001

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/comparison-of-the-two-subtypes-of-axial-spondyloarthritis-patients-fulfilling-the-imaging-arm-based-on-radiographic-and-mri-findings/