POS1204 LOW POSITIVITY RATE IN ANTIBODY SARS-COV2 TESTS IN PATIENTS WITH RHEUMATIC DISEASES TREATED WITH RITUXIMAB. A CASE CONTROL STUDY OF A HIGH IMPACT SARS-COV2 INFECTION AREA.
Authors: A. García Fernández, P. Morán Álvarez, J. Bachiller-Corral, M. Vázquez Díaz
Journal: Annals of the Rheumatic Diseases (2021)

Background: Diagnosis of previous SARS-COV2 infection may be challenging in immunocompromised patients. Objectives: To analyze positivity rate to SARS-COV2 antibody tests (SC2AT) in patients diagnosed of rheumatic diseases (RMD) treated with Rituximab. Methods: We conducted a case-control study of patients diagnosed of RMD followed in a referral hospital in Madrid, Spain. Positivity rate to IgG-SC2AT were analyzed in Rituximab-treated patients (RTX) compared with patients treated with TNF inhibitors (TNFi) and/or conventional DMARDs (cDMARDs) (N-RTX). We included patients that received Rituximab in the previous year to a confirmed SARS-COV2 infection (defined as a positive polymerase chain reaction test (PCR) and/or compatible chest Xray), to a suspected SARS-COV2 infection (2 or more symptoms) or to SC2AT determination. Patients with RMD treated with other biological DMARDs (bDMARDs) rather than Rituximab or TNFi were excluded. Results: We included 152 patients with RMD who underwent a SC2AT. Main characteristics are reported in Table 1. Among RTX and N-RTX, 4/48 (8.3%) and 35/104 (33.7%) showed a positive IgG-SC2AT, respectively. Four out of 104 (38.5%) N-RTX tested positive without previous symptoms. No asymptomatic infection was diagnosed among RTX. Univariable analysis showed a lower rate of positivity to SC2AT in confirmed and suspected infection among RTX [Positive IgG-SC2AT in confirmed infection: RTX 4/10 (40%), N-RTX 16/20 (80%); p=0.045. Positive IgG-SC2AT in suspected infection: RTX 0/3 (0%), N-RTX 15/18 (83.3%); p=0.015]. A logistic binary regression identified previous symptoms [OR 61.2, 95CI(13.3-280.6) p=0.0001], male sex [OR 4.8, 95CI(1.3-17.8) p=0.02], non-rituximab treatment [OR 19.7, 95CI(3.6-106.3) p=0.001] as independent factors associated with a higher probability of positive IgG-SC2AT. Age, previous PCR status, corticosteroid and cDMARD use showed no statistical significance. This model accounted for 47.6% of positive cases. Table 1. Main characteristics. AS, axial spondylitis; bDMARDs, biological disease-modifying anti-rheumatic drugs; cDMARDs, conventional DMARDs; COPD, Chronic obstructive pulmonary disease; CVD, Cardiovascular disease; IMM, immune-mediated myositis; JIA, Juvenile Idiopathic arthritis; PsoA, Psoriatic Arthritis; RA, Rheumatoid Arthrtis; SLE, Systemic Lupus Erythematosus; SSc, Systemic Sclerosis; SSj, Sjogren Syndrome. Rituximab (RTX ) Non-Rituximab (N-RTX ) p value Patients, n (% ) 48 (31.6) 104 (68.4) Age , years, median (IQR) 65 (54-72) 60 (47-71.8) p= 0.190 Female, n (%) 38 (79.2) 74 (71.2) p=0.297 Diagnosis, n (%) p=0.2 - RA 20 (41.7) 42 (40.4) - SSj 4 (8.3) 6 (5.8) - RA SSj 3 (6.3) 0 (0) - SLE 4 (8.3) 8 (7.7) - Vasculitis 7 (14.6) 13 (12.5) - IMM 1 (2.1) 4 (3.8) - JIA 2 (4.2) 3 (2.9) - SSc 7 (14.6) 15 (14.4) - AS 0 (0) 4 (3.8) - PSoA 0 (0) 5 (4.8) - Others a 0 (0) 4 (3.8) Comorbidities, n (% ) - Hypertension 18 (37.5) 34 (32.7) p=0.561 - Diabetes 5 (10.4) 10 (9.6) p=0.878 - Dyslipidemia 18 (37.5) 30 (28.8) p=0.286 - COPD/asthma 6 (12.5) 4 (3.8) p=0.049* - CVD 11 (35.4) 25 (24) p=0.831 Interstitial lung disease, n (% ) 17 (35.4) 8 (7.7) p&lt;0.0001* Corticosteroids use, n (%) 26 (54.2) 33 (31.7) p=0.008* cDMARDs use, n (%) 27 (56.3) 73 (70.2) p=0.092 bDMARDs, n (%) - - None 0 (0) 83 (79.8) - TNF inhibitors 0 (0) 21 (20.2) - Rituximab 48 (100) 0 (0) Previous positive PCR, n (% ) - Time from positive PCR to SC2AT, days, mean ±SD 8 (16.7) 47.4 (38.7) 20 (19.2) 65.1 (49) p=0.191 p=0.368 Previous symptoms, n (% ) - Time from symptom onset to SC2AT, days, mean ±SD 13 (27.1) 130.3 ±91.1 36 (34.6) 93.5 ±72.6 p=0.356 p=0.15 COVID, n (%) p=0.183 - Non suspected 35 (72.9) 66 (63.5) - Suspected 3 (6.3) 18 (17.3) - Confirmed 10 (20.8) b 20 (19.2) a Including gout, polymyalgia rheumatica. b Two patients had negative PCR but compatible symptoms and chest X-Ray. Conclusion: RTX had a lower rate of positivity to IgG-SC2AT compared to N-RTX. Previous symptoms, male sex and non-RTX treatment were independently associated with higher probability of positive IgG-SC2AT. Disclosure of Interests: None declared.