Background: The use of bone scintigraphy (Sc) in spondyloarthritis (SpA) as a technique for diagnosis, assessment of activity and treatment decision has been questioned by the scientific community. Due to its low cost compared to Magnetic Resonance Imaging - MRI (the gold standard) ¹ , some studies proposed to evaluate Sc’s diagnostic accuracy. These studies have shown that Sc has a low diagnostic sensitivity of 50-55% ² . Also, there is a poor correlation between symptoms and scintigraphic uptake ³ . We aimed to evaluate the use of Sc for management and follow-up of patients with SpA.

Objectives: To determine if Sc activity correlates with patients’ complaints (peripheral and axial), inflammatory markers, disease activity scores and whether it influenced physicians’ treatment decisions during the follow-up of the disease.

Methods: We performed a retrospective review of all patients at our department with SpA with at least one Sc from 2018 to 2020. The following variables were analyzed: demographic data, spondyloarthropathy subtype (ankylosing, enteropathic, psoriatic and undifferentiated SpA), axial or peripheral pain, Sc findings (inflammatory vs no-inflammatory activity), inflammatory markers (sedimentation rate - ESR and C-Reactive Protein - CRP), disease activity scores within one year since the Sc (Ankylosing Spondylitis Disease Activity Score with Erythrocyte Sedimentation Rate - ASDAS-ESR and Bath Ankylosing Spondylitis Disease Activity Index - BASDAI) and treatment at the time of the Sc (non-steroidal anti-inflammatory drugs, conventional synthetic disease-modifying antirheumatic drugs (DMARDs), target synthetic DMARDs and biologic DMARD. Treatment decisions (escalation, de-escalation or maintenance) in accordance to Sc results were also reviewed.

We used the non-parametric Mann-Whitney’s U test for comparisons between ordinal or numerical variables. For correlations between categorical variables we used the Fisher’s exact test and the χ2-independence test. Tests with p < 0.05 were statistically significant.

Results: Fifty-five patients were reviewed, 75% women; median age of 48 years. Seventy-one percent had ankylosing SpA, 15% enteropathic SpA, 5% psoriatic SpA, 5% undifferentiated and 4% reactive SpA. Sixty-two percent of the patients had both axial and peripheral pain and 24% only axial complaints. Sixty-two percent of the patients had a Sc with no inflammatory changes, 27% had peripheral and 25% had axial inflammatory changes; 15% had evidence of both peripheral and axial inflammation. For ankylosing SpA, the median ASDAS-ESR was 2.89 and according to the BASDAI, 66% had active disease. The median CRP and ESR in patients with inflammatory vs a normal Sc was not different ( p =0.02 vs p =0.36, respectively). Similarly, Sc findings were not correlated with patients’ axial ( p =0.10) or peripheral pain ( p =1.0), neither with the ASDAS-ESR ( p =0.29) or the BASDAI ( p =0.29). There was no correlation between inflammatory activity in Sc and the decision to maintain, escalate or de-escalate treatment ( p =0.65), including the decision to start a biological DMARD ( p =1.0) or to switch between biological DMARDs ( p =0.19).

Conclusion: There was no correlation between Sc findings and ESR, patients’ complaints, disease activity or treatment decisions. Considering previous research showing a low diagnostic sensitivity, our findings seem to support a limited role of bone Sc for the follow-up and management of patients with seronegative SpA.

REFERENCES:

[1]Khmelinskii N, Regel A, Baraliakos X. The Role of Imaging in Diagnosing Axial Spondyloarthritis. Front Med . 2018;5. doi:10.3389/fmed.2018.00106

[2]Poddubnyy D. Classification vs diagnostic criteria: the challenge of diagnosing axial spondyloarthritis. Rheumatology . 2020;59(Supplement_4):iv6-iv17. doi:10.1093/rheumatology/keaa250

[3]Shim JS, Kim C, Ryu JJ, Choi SJ. Correlation between TM joint disease and rheumatic diseases detected on bone scintigraphy and clinical factors. Sci Rep . 2020;10(1):4547. doi:10.1038/s41598-020-60804-x

Disclosure of Interests: None declared.