POS0516 REDEFINING THE CLINICAL AND LABORATORY FEATURES OF RHEUMATIC PLEURAL EFFUSION: A 30-CASE SERIES
Authors: S. Minoda, R. Sada, S. Matsushita, Y. Nakayama, H. Akebo, Y. Tsugihashi, H. Ishimaru, K. Hatta
Journal: Annals of the Rheumatic Diseases (2021)

Background: Rheumatoid pleural effusion (RPE) is a common extra-articular complication in patients with rheumatoid arthritis (RA). Previous studies have shown that RPE usually occurs in middle-aged men with rheumatoid factor (RF)-positive RA. RPE usually has features of pleural fluid acidosis, high lactate dehydrogenase (LDH) levels, and very low glucose levels (1) . However, to the best of our knowledge, these findings were based on very few case series and reports, and most of these reports were published by the early 2000s (1, 2) . Objectives: To investigate the clinical and laboratory characteristics and typical clinical courses of patients with RPE in a single centre of Japan since the beginning of the 21st century. Methods: Medical records of RPE patients were retrospectively reviewed between May 2006 and September 2020. RPE was identified by fulfilling these five conditions: (1) confirmation of the RA diagnosis; (2) having an exudative pleural effusion according to Light’s criteria; (3) negative results of pleural fluid culture; (4) negative results of pleural fluid cytology; and (5) exclusion of a parapneumonic effusion or empyema defined as no antibiotic use or ineffectiveness of antibiotics during the clinical course. Patients were divided into two groups according to their age at diagnosis: &lt;60 years (Group A) and ≥60 years (Group B). Results: A total of 30 cases of RPE were included in the study. The median age was 71 years (interquartile range [IQR], 66–78 years). Of these patients, 16 (53%) were women. The median disease duration of RA was 98 months (IQR, 8–162 months). The two groups comprised six patients aged &lt;60 years old and 24 patients ≥60 years. The median age was 54 years (IQR, 49–56 years) in Group A and 74 years (IQR, 69–78 years) in Group B. The median disease duration of RA was longer in Group B than that in Group A (132 vs . 3 months, p=0.008). Compared with Group A, Group B had fewer patients with fever (14% vs . 83%, p=0.003), and had lower serum C-reactive protein levels (3.3 vs. 11.1 mg/dL, p=0.03). Moreover, Group B was more likely to show mild inflammatory pleural fluids with higher pH (7.5 vs. 7.2, p=0.005) and lower LDH levels (155 vs . 1810 IU/L, p=0.046). Corticosteroids were started or increased in five (83%) and nine (38%) patients, and biologic disease-modifying anti-rheumatic drugs were started in one (17%) and two (8%) patients in groups A and B, respectively. One patient (16%) died within 5-years in Group A, and seven patients (29%) died in Group B. Conclusion: In contrast to previous studies, RPE was seen in older patients as well as middle-aged adults, and the pleural fluid analysis in older patients with RPE showed milder inflammation than the middle-aged patients. References: [1]Balbir-Gurman A, et al. Semin Arthritis Rheum. 2006 Jun; 35(6): 368-78. [2]Faurschou P, et al. Thorax. 1985 May; 40(5): 371-5. Table 1. Comparison of clinical and laboratory findings between Group A and Group B. Group A (n=6) Group B (n=24) P value Age (years) 54 [49-56] 74 [69-78] Female 2 (n=6, 33.3) 14 (n=24, 58.3) 0.38 Disease duration of RA (months) 3 [1-9] 132 [44-199] 0.008 Fever ≥37.0°C 5 (n=6, 83.3) 3 (n=22, 13.6) 0.003 Serum CRP (mg/dL) 11.1 [5.6-1.4] 3.3 [0.9-10.5] 0.03 RF (IU/mL) 100 [19-816] 63 [23-193] 0.95 Anti-CCP ab positive 5 (n=6, 83.3) 12 (n=15, 80) 1.00 Pleural fluid analysis pH 7.2 [7.2-7.2] 7.5 [7.4-7.5] 0.005 LDH (IU/L) 1810 [594-2932] 155 [123-346] 0.046 Glu (mg/dL) 59 [10-123] 105 [91-122] 0.42 Tp (g/dL) 5.1 [4.9-5.6] 4.6 [3.6-5.2] 0.21 Number of cells (/μL) 5235 [3353-9300] 3300 [1490-5008] 0.27 Glu/serum Glu 0.41 [0.09-0.99] 1.05 [0.85-1.15] 0.71 Started or increased CS 5 (n=6, 83.3) 9 (n=24, 37.5) 0.18 Started bDMARDs 1 (n=6, 16.6) 2 (n=24, 8.3) 0.50 Died within 5 years 1 (n=6, 16.6) 7 (n=24, 29.1) 1.00 Data are median [interquartile range], or number (total number, percent). Abbreviations: RA, rheumatoid arthritis; CRP, C-reactive protein; RF, rheumatoid factor; Anti-CCP ab, anti-cyclic citrullinated peptide antibodies; LDH, lactate dehydrogenase; Glu, glucose; Tp, total protein; CS, corticosteroid; bDMARDs, biologic disease-modifying anti-rheumatic drugs Disclosure of Interests: None declared