POS0963 POWER AND SPECTRAL DOPPLER ULTRASOUND AS A SCREENING TOOL IN THE DIAGNOSTIC COURSE OF SUSPECTED AXIAL SPONDYLOARTHRITIS: PRELIMINARY DATA FROM A LARGE MONOCENTRIC COHORT
Authors: P. Falsetti, E. Conticini, C. Baldi, M. Bardelli, R. D’alessandro, S. G. Al Khayyat, M. A. Mazzei, L. Cantarini, B. Frediani
Journal: Annals of the Rheumatic Diseases (2021)

Background: Sacroiliac joints (SIJs) involvement is a characteristic feature of Spondylarthritis (SpA). Magnetic resonance imaging (MRI) has been included in the new Assessment of SpA International Society (ASAS) criteria for the classification of non-radiographic axial SpA. Power Doppler ultrasound (PDUS) and spectral Doppler US have been used in few works, also from our group, to evaluate the inflammatory activity of the SIJs, in comparison with MRI, with different results. Objectives: We aimed to evaluate the value of PDUS with spectral wave analysis (SWA) in the assessment of suspected active sacroiliitis (SI). PDUS of SIJs was used as a screening tool alongside the routine PDUS assessment of peripheral joints. Methods: 143 patients (114 females and 29 males, mean age 46,2 years, mean BMI 25.9) with new onset of inflammatory back pain (IBP), were included. Peripheral symptoms were allowed. Every patient underwent a PDUS examination of SIJs as previously reported. The sonographer was blinded to the clinical data. An Esaote Twice US machine, with convex 1-8 MHz and linear 6-18 MHz probes, was used, with standardized parameters. PD signals detected in the SIJs, were scored with a 3-points scale: 0= absence of signals, 1= isolate vessels, 2= more than one vessel. The signals were also classified as intra-articular (vascularity from deep joint and inter-osseous ligament) or peri-articular (vascularity along posterior sacroiliac ligament). SWA was applied to the same vessels calculating the Resistive Index (RI) (Figure 1). A PDUS diagnosis of active SI was made with a grade 1 of vascularity and RI&lt;0,60, or grade 2 of vascularity and RI&lt;0,70. PDUS multi-site examination of peripheral joints and entheses was also performed; entheseal involvement was scored with Belgrade Ultrasound Enthesitis Score (BUSES) and as global enthesitic charge (GEC). Every patient underwent MRI of SIJs within 2 weeks, and before to start pharmacologic treatment. The non-parametric Spearman rank test and univariate linear regression analysis was applied using InStat GraphPad statistical package. Results: A time of 5-8 minutes was sufficient to set and to complete PDUS/SWA examination on both SJJs. All patients considered this examination quick, not painful and substantially comfortable. PD signals were detected in 124 patients (mean RI 0,56). Bone marrow edema (BME) lesions (active SI on MRI) were detected in 94 patients. A final diagnosis of SpA was made in 103 patients (81 females, 22 males). Among SpA patients 24 had psoriasis, 3 inflammatory bowel disease, 3 uveitis, 5 were B27+, and they had mean BUSES of 4,1 and GEC of 1,2. The mean SIJs PDUS score was 1,3 in SpA and 0,52 in not-SpA patients. The mean SIJs RI was 0,53 in SpA and 0,68 in not-SpA patients. A significant correlation was demonstrated between MRI and PDUS diagnosis of SI (r=0,6486, p&lt;0,0001), between MRI diagnosis and PD grading (r=0,4937, p&lt;0,0001). The split analysis of peculiar parameters of imaging between the two methods also showed significant correlation: periarticular vascularity showed correlation with post-contrast MRI evidence of posterior capsulitis and enthesitis (p=0,001), as SIJs BME correlated with intra-articular PD signals (p&lt;0,001). RI from SWA analysis was inversely correlated with MRI diagnosis of active SI (p&lt;0.0001). SIJs PD demonstrated a significant correlation with SIJs pain (p&lt;0,001), but not with inflammatory reactants, GEC, peripheral synovitis, and a weak correlation with BUSES (p=0,038). Conclusion: SIJs PDUS/SWA may be an optional method for preliminary screening of active SI, as a feasible, cheap and an accurate diagnostic tool, compared with MRI as a gold standard for nr-Axial SpA. PD US in SI. Right SI joint with a PD signal within inter-osseous ligament (curved arrow), where spectral PD analysis shows a RI of 0,62. Normal vessels (with high RI, unshowed) can be observed into the first sacral foramen (arrowhead). The first sacral apophysis (arrow) protrudes from the sacrum profile. Disclosure of Interests: None declared.