AB0803 SYNOVIAL INTERLEUKIN-8 LEVELS ARE ASSOCIATED TO RADIOGRAPHIC SEVERITY OF KNEE OSTEOARTHRITIS. A CROSS-SECTIONAL STUDY
Authors: Silvia Garcia-Cirera, Joan Calvet, Cristobal Orellana, Noemí Navarro, Maria Garcia Manrique de Lara, Jordi Gratacos-Masmitja
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Radiographic severity is used in routine clinical practice to evaluate knee osteoarthritis (KOA) structural damage. There are no conclusive studies on the associations between synovial inflammatory markers and the different features of radiographic damage in KOA. <h3>Objectives</h3> To evaluate the association between inflammatory markers in synovial fluid with the different features of radiographic severity in patients with KOA. <h3>Methods</h3> Cross-sectional study of 114 female patients aged 50-85 with symptomatic primary KOA with significant joint effusion (&gt;4 mm at midline patellar line) confirmed by ultrasound. The following information was collected: age, KOA symptoms duration, body mass index; plain standing knee Rx in semi-flexion were evaluated for radiographic severity by modified OARSI atlas evaluating separately osteophytes (OPH) and joint space narrowing (JSN). The OPH score was obtained searching for marginal osteophytes in both medial and external femoral condyles and tibial plateaus, scoring 0 to 3 in each quadrant, for a total score ranging from 0-12. Due to the high number of different scores obtained, and sometimes with a low number of patients, we grouped osteophytes scores 1-2 as mild, 3-6 as moderate and seven or more as severe osteophyte count. The JSN score was calculated in both medial and lateral knee compartments, grading the joint space 0 to 3 in each one, for a total score ranging from 0 to 6. A JSN score of 0 was considered as normal, 1-2 as moderate and 3 or more as high JSN severity. Five inflammatory markers: TNF alpha, high sensitivity C-reactive protein (hsCRP), interleukin 6 (IL-6), interleukin 8 (IL-8) and calprotectin were measured by ELISA following manufacturer recommendations for synovial fluid dilutions. A comparison between medians of the three groups was carried out and a multivariate analysis controlled by age, symptom duration, BMI and all five inflammatory markers were performed. <h3>Results</h3> A significant association for symptom duration and synovial IL8 was observed for osteophytes (p&lt;0.0001 and p&lt;0.05, respectively), which remained after adjustment (p=0.002 and p=0.037, respectively). Regarding symptom duration, the differences were related to high severity osteophyte index, compared to moderate or low stages (p= 0.0005 and p=0.002, respectively), while for IL-8 the differences were associated to a low OPH severity index compared with a moderate osteophyte score (p=0.011), with IL-8 levels approximately 33% less than the moderate OPH score (p=0.011). For JSN, in the adjusted analysis, patients with a high JSN score had synovial IL-8 levels of 40% more than those with JSN 0 (p=0.035), while no differences were found between the moderate JSN score and the other two degrees. Regarding hsCRP, 30% higher levels were found in patients with a JSN moderate degree compared with JSN 0 (p=0.033), while no significant differences were observed between severe and the other two degrees. <h3>Conclusion</h3> Interleukin-8 IL 8 was the inflammatory marker associated to radiographic severity as evaluated by osteophyte count and joint space narrowing score on plain radiography in patients with knee osteoarthritis. <h3>Disclosure of Interests</h3> Silvia Garcia-Cirera: None declared, Joan Calvet: None declared, CRISTOBAL ORELLANA: None declared, Noemí Navarro: None declared, Maria Garcia Manrique de Lara: None declared, Jordi Gratacos-Masmitja Grant/research support from: Pfizer Inc, Consultant for: Pfizer Inc, Speakers bureau: Pfizer Inc