AB0150 ACPA-STATUS AND RHEUMATOID ARTHRITIS: MUCH MORE TO BE REVEALED!
Authors: K. Maatallah, S. Miri, H. Ferjani, D. Ben Nsib, W. Triki, A. Dallegi, D. Kaffel, W. Hamdi
Journal: Annals of the Rheumatic Diseases (2021)

Background: Anti-citrullinated protein antibodies (ACPA) are commonly associated with Rheumatoid arthritis (RA). RA is, therefore, classified as immunopositive or immunonegative, with disparate mechanisms in predisposition. Objectives: Our study aimed to determine the baseline characteristics and differences of ACPA-positive and ACPA-negative RA. Methods: We conducted a cross-sectional study including 224 patients with RA. All patients fulfilled the 2010 American College of Rheumatology/European League Against Rheumatism RA classification criteria. The patients were divided according to their ACPA status into two groups: ACPA-positive group (G1) and ACPA-negative group (G2). We compared clinical, radiological, and laboratory findings between the two groups, as well as extra-articular manifestations, comorbidities including fractures and osteoporosis. The Fracture Risk Assessment Tool (FRAX) was used to estimate the 10-year probability of major osteoporotic fracture (MOF) and also hip fracture (FH). Results: Of the 224 patients, 31.6% were negative for ACPA (n=71). Female predominance was found in both groups with a sex ratio of 0.25 (p=0.203). ACPA-negative subjects were younger (57±11 versus 59±12 years) (p= 0.305). The initial presentation of RA was different between the two groups without reaching statistical significance. In the ACPA-negative group, alteration of general condition was more frequent (16.9% in G2 versus 13.7% in G1) (p=0.533), with a tendency to oligo-articular onset (18.5% in G2 versus 6.7% in G1) (p=0.737). ACPA-positivity was more associated with an acute start of symptoms (10.4% in G1 versus 8.4% in G2) (p=0.639) There was no significant difference in the mean DAS28-VS (5.2±1.1 in G2 versus 5.5±1.3 in G1) and DAS28-CRP levels (5±1 in G2 versus 5.3±1.2 in G1) (p=0.069 and p=0.098 respectively). ACPA-positive RA was, however, significantly associated with more structural joint damage: erosions (55.9±53 in G1 versus 78±36 in G2, p=0.01), joint space narrowing (50.4±45.5 in G1 versus 33.1±36.6 in G2, p=0.003), Sharp/van der Heijde radiographic score (126.6 ±103.2 in G1 versus 88.8±81.5 in G2, p=0.004). ACPA-positive RA patients had more atlantoaxial dislocation: 20.2% in G1 versus 7% in G2 (p=0.012). There was no significant difference in hip involvement (9.8% in G1 versus 14% G2) (p=0.344). There were no significant differences in extra-articular manifestations between the two groups: Rheumatoid nodules (10.4% in G1 versus 18.3% in G2) (p=0.891), Sjögren’s syndrome (16.3% in G1 versus 16.9% in G2)(p=0.715), amyloidosis (0.6% in G1) (p=1), pulmonary fibrosis (5.8% in G1 versus 4.2% in G2) (p=0.757), neurological signs (4.5% in in G1 versus 5.6% in G2) (p=0.733), anaemia (5.8% in G1 versus 1.4% in G2) (p=0.175). When analyzing comorbidities, no significant differences were found: diabetes (10.4% in G1 versus 18.3% in G2) (p=0.103), cardiovascular diseases (19.6% in G1) (p=1), neurological diseases (0.06% in G1 versus 1.4% in G2) (p=0.534), dysthyroidism (2.6% in G1 versus 5.6% in G2) (p=0.267), dyslipidemia (3.2% in G1 versus 4.2% in G2) (p=0.711), cancer (1.3% in G1) (p=1). There were neither significant differences in the prevalence of fracture (21.5% in G1 versus 18.3% in G2) (p=0.574), and osteoporosis (23.6% in G1 versus 29.5% in G2) (p=0.347), between the two groups. However, ACPA-positive patients presented with a significantly higher FRAX score of MOF (2±2.8 in G1 versus 1.2±1 in G2) (p=0.006), and FRAX score of FH (0,9±1.8 in G1 versus 0.3±0.5 in G2) (p=0.003). Conclusion: ACPA status appears to influence both the clinical presentation and radiological progression of RA patients. ACPA-positive patients present with an acute start of symptoms, with more structural damages and atlantoaxial dislocation. Comorbidities, including osteoporosis, does not seem affected by ACPA status. However, regardless of osteoporosis, ACPA-positivity is associated with a higher probability of major osteoporotic and hip fractures. Further research is needed to clarify this relationship. Disclosure of Interests: None declared