Session Information
Session Type: Abstract Submissions (ACR)
Background/Purpose:
A proportion of patients with non-radiographic axial spondyloarthritis (NR-AxSpA) progress to AS but the predictors of progression have not been well established. We studied the predictors of progression of NR-AxSpA.
Methods:
Patients with NR-AxSpA who were followed in two major SpA centers were enrolled in this study. Patients are classified as NR-AxSpA if they do not satisfy the modified New York Criteria for AS but satisfied the ASAS criteria for axial SpA. All patients had two X-rays of the pelvis separated by at least 1.5 years. All patients were followed with a standardized protocol and were assessed on an annual basis. Disease activity was assessed by Bath AS Disease Activity Index (BASDAI), ESR and CRP. Markers of inflammation were averaged over the period of follow-up to estimate the ongoing level of inflammation. HLA-B27 was done in all patients and MRI of the spine was done as clinically indicated. Smoking pack-year history was collected. Three readers, blinded to patient details scored the pelvis radiographs using the New York grading system for sacroiliitis. Progressors were defined as those who had significant increase in SI joint score (2 grades). Logistic regression analysis was done to identify predictors of progression.
Results:
Fifty-one patients (51% females and 75% HLA-B27 positive) qualified for the study and were followed for a mean (± SD) duration of 3.6 ± 2.1 years. The mean disease duration was 9.5 ± 7.7 years. The baseline and time averaged BASDAI were 5.1 ± 2.0 and 4.8 ± 2.1 respectively. Iritis, inflammatory bowel disease (IBD) and Psoriasis were present in 29.4%, 7.8% and 13.7% respectively. Except for one patient, all others had inflammatory back pain (IBP). Only 14 patients were smokers with 2.1 ± 6.5 pack-years history. Only 6 patients had significant progression and 4 patients satisfied the Modified New York criteria at last follow-up. Except for one patient who progressed at 2.5 years, all others did so after 6 years of follow-up.
Progressors are compared to non-progressors in Table 1. All patients who progressed were HLA-B27 positive. Patients with iritis had a relative risk of progression of 4.8 (1.0, 23.5; p=0.053). Progressors had significantly higher baseline BASDAI (p=0.04, Median Test). Those who progressed had longer follow-up and after correction for this, logistic regression analysis showed significant association of progression with smoking pack years with an OR of 1.2 (1.03-1.4, p=0.02). In multivariate logistic regression analysis including all baseline parameters, the only significant variable associated with progression was the duration of follow up.
Conclusion:
Over a mean follow up of 3.6 years, 8% of patients with NR-AxSpA progressed to AS. Smoking appears to be a risk factor for significant progression of SI joint scores. HLA-B27, higher baseline BASDAI and iritis were more common in progressors.
Table 1. Comparison of progressors with non-progressors
|
Variable
|
Progressors (N=6) |
Non-progressors (N=45) |
p |
|
Median Age of Onset (IQR, years) |
29 (18, 42) |
28 (22, 36) |
ns |
|
HLA-B27 (%) |
6 (100) |
32 (71) |
0.051 |
|
Female (%) |
3 (50) |
23 (51) |
ns |
|
Median Disease Duration (IQR, years) |
14 (11, 17) |
7 (2, 16) |
ns |
|
Baseline Median ESR (IQR, mm per hour) |
8 (5, 12) |
7 (3, 19) |
ns |
|
Baseline Median CRP (IQR mg/L) |
3 (3, 4) |
3 (3, 5) |
ns |
|
Average Median ESR (IQR, mm per hour) |
5 (3, 8) |
7 (3, 18) |
ns |
|
Average Median CRP (IQR mg/L) |
3 (2, 4) |
3 (2, 4) |
ns |
|
Baseline Median BASDAI (IQR) |
6.2 (6, 7) |
5 (3, 7) |
0.04 |
|
Average Median BASDAI (IQR) |
6 (5, 7) |
5 (3, 7) |
ns |
|
Iritis (%) |
4 (67) |
11 (24) |
0.054 |
|
IBD (%) |
1 (17) |
3 (7) |
ns |
|
Psoriasis (%) |
2 (33) |
5 (11) |
ns |
|
Peripheral Arthritis (%) |
4 (67) |
33 (73) |
ns |
|
Enthesitis (%) |
4 (67) |
30 (67) |
ns |
|
Dactylitis (%) |
0 |
3 (7) |
ns |
|
IBP (%) |
6 (100) |
44 (98) |
ns |
|
Smoking (%) |
3 (50) |
11 (24) |
ns |
|
Smoking (Median, IQR Pack Years) |
1 (0, 10) |
0 (0, 0) |
ns |
|
Biologics (%) |
2 (33) |
25 (56) |
ns |
|
Biologics Median Duration (IQR, Yrs) |
3 (0, 7) |
3 (0, 4) |
ns |
|
Median Gap between X-rays (IQR ,Yrs) |
7 (4, 9) |
3 (2, 4) |
ns |
Disclosure:
N. Haroon,
None;
L. S. Gensler,
None;
D. Wallis,
None;
A. Anton,
None;
G. Yoon,
None;
R. D. Inman,
None.
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