POS0573 MUSCULOSKELEATAL ULTRASOUND STUDIES ARE CRITICAL FOR DETECTING SERONEGATIVE INFLAMMATORY ARTHRITIS

Abstract

BackgroundThe autoantibody status of rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (anti-CCP Ab) has gained widespread recognition for its role in the diagnosis of rheumatoid arthritis (RA) based on the latest diagnostic criteria for RA.1 However, in early disease, the rates of antibody expression have been reported as low as 50%2, rendering early diagnosis of RA difficult. Furthermore, the nature of seronegative rheumatoid arthritis is unknown, though it is presumed to have less aggressive disease course as compared to its seropositive counterparts. Musculoskeletal (MS) ultrasound studies have been widely used in recent clinical practice to assess soft-tissue abnormalities of the joints and disease states in RA, such as synovitis and bone erosions. MS ultrasound studies were recently shown to be more sensitive to detect early synovial changes and erosions than other radiographic methods while maintaining cost-effectiveness.3-5 We hypothesize that MS ultrasound studies are more sensitive to detecting inflammatory changes in seronegative inflammatory arthritis, which is often subclinical in presentation.ObjectivesTo assess the role of MS ultrasound studies in detecting early inflammatory changes in the joints and diagnosing seronegative inflammatory arthritis.MethodsA retrospective electronic medical record review was performed of all patients at the two University at Buffalo rheumatology clinics who underwent MS ultrasound studies after complaining of multiple joint pain. All these patients were previously seen and evaluated by at least one other medical provider, who found no evidence of inflammatory arthritis on physical examination. These patients did not meet diagnostic criteria for rheumatoid arthritis due to a lack of gross joint swelling and/or positive serological makeup. As part of their clinical care, they were referred to obtain MS ultrasound studies to rule out inflammatory arthritis. All patients were de-identified at initial data collection. Information pertaining to the patients’ 1) demographics (gender, age, ethnicity, etc.), 2) findings of MS ultrasound studies, and 3) serological studies (RF, anti-CCP Ab, HLA-B27) was collected and tabulated.ResultsOf the 363 patients who underwent MS ultrasound studies, 280 of them (77.1%) of them were found to have synovial hypertrophy [minimal = 23%, mild = 46%, moderate = 29%, severe = 2%] in bilateral MCP, PIP, carpal, and/or MTP joints, therefore conferring a diagnosis of inflammatory arthritis. The average age of these 280 patients was 48.35 ± 14.86 years old at the time of diagnosis, with female to male ratio of 4.38:1. Surprisingly, of these 280 patients with evidence of inflammatory arthritis, 69 (24.6%) of them were found to have joint erosions with either MCP or MTP joints, supporting a diagnosis of advanced inflammatory arthritis with erosive disease. The erosions were predominantly located in MTP joints (77.1%) as compared to MCP joints (22.9%). Therefore, our findings clearly demonstrated distinct clinical and ultrasonography features of seronegative inflammatory arthritis (SNIA) as compared to seropositive RA.ConclusionMS ultrasound studies are more sensitive to and critical for detecting inflammatory changes and joint damages in SNIA due to its subclinical presentation. Based on our findings, SN IA is underdiagnosed in individuals who complain of joint pain without gross synovitis. SNIA also likely has distinct pathophysiology that needs further characterization.