Background/Purpose

The diagnosis of AxSpA is not easy and there are cases of overlap with fibromyalgia for example. Anti-TNF have been shown to have great efficacy in AxSpA, and primary inefficacy is rare. Do patients who have primary inefficacy to anti-TNF, really have a diagnosis of AxSpA?

Objective

To assess  the evolution and final diagnosis of all patients with primary inefficacy to anti-TNF in AxSpA over a period of two years in one tertiary referral center, with a follow up of five years.

Methods

Systematic retrospective study of all patients receiving an anti-TNF for AxSpA in one tertiary referral  centre (ref). Patients had AxSpA according to the rheumatologist and were started on a first course of anti-TNF according to usual practice. Primary inefficacy was defined by the rheumatologist’s opinion after three months of treatment by anti-TNF, when the treatment was then discontinued. Five years later, these patients were recontacted and were seen in outpatient clinic if possible, filled in questionnaires including FIRST for fibromyalgia, and a final diagnosis was defined.

Results

Of 222 patients receiving a first anti-TNF for AxSpA, 27 (12.2%) were considered as having primary inefficacy to their first anti-TNF. The characteristics of these patients were slightly different from the others, with more females (48 vs 27%, p=0.04), older age (46 vs 40 yrs; p=0.04), higher BASFI (68 vs 42, p=0.001) and less increased CRP (50% vs 78%, p=0.008). Among the 27 patients, a second anti TNF was prescribed for 16 (59.2%) patients, 7 (7/16=43.7%) had primary inefficacy to the second anti-TNF  and retention rate of the second anti-TNF at one year was 50%.

At the 5 year follow-up, 14 patients were seen in outpatient clinic and 9 follow-up medical files were available; 4 patients could not be evaluated (2 were lost to follow-up and 2 refused).

The diagnosis of AxSpA was confirmed for 20/23 (86.9%) patients according to the ASAS criteria and 23/23 (100%) patients according to the rheumatologist; but 16/23 (69.6%) had at least one other cause of pain/symptoms: 10 (43.5%) had osteoarthritis, 7 (30.4%) patients had depression and 3 (13.0%) had fibromyalgia. 

Conclusion

Primary inefficacy to anti-TNF in AxSpA is rare, and patients with primary inefficacy have slightly different characteristics from the other AxSpA patients. Long-term follow-up indicates most of these patients have a definite diagnosis of AxSpA but often have other causes of pain/symptoms. We suggest patients with primary inefficacy to anti-TNF should be screened for comorbidities like fibromyalgia, osteoarthritis or depression that may interfere with AxSpA impact and assessment.

Reference

Dadoun and al . Switching between tumor necrosis factor blockers in spondyloarthritis : a retrospective monocenter study of 222 patients . Clin Exp Rheumatol ;29:1010-3

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/do-patients-diagnosed-as-axial-spondyloarthritis-axspa-who-have-primary-inefficacy-to-anti-tnf-really-have-axspa-a-five-year-follow-up-study-of-27-patients-with-primary-inefficacy-to-anti-tnf/