AB0586 PREVALENCE OF EARLY SYMPTOMATIC KNEE OSTEOARTHRITIS ACCORDING TO THREE CLINICAL CLASSIFICATION CRITERIA
Authors: M. Törnblom, A. Bremander, K. Aili, M. Andersson, A. Nilsdotter, E. Haglund
Journal: Annals of the Rheumatic Diseases (2021)

Background: Knee osteoarthritis (KOA) is a heterogeneous disease. Different classification criteria for symptomatic KOA (SKOA) have been proposed. Determining the prevalence and comparing the different criteria of SKOA in patients with knee pain will serve as a base when studying the predictive ability of these criteria in a longer perspective. Objectives: To study the prevalence of SKOA in individuals with knee pain according to three different classification criteria: the American College of Rheumatology (ACR), (1), the European League Against Rheumatism (EULAR)(2), and the National Institute for Health and Care Excellence (NICE) (3). Methods: Baseline data from an ongoing longitudinal study (HALLOA) including 296 individuals with knee pain, recruited by advertisement, were analysed. The individuals were categorized according to the classification criteria of SKOA (ACR, EULAR and NICE) based on age, clinical examination (crepitation), and self-reported data from KOOS (pain, symptoms, ADL, and sport/recreation), and dichotomized as fulfilling the criteria (SKOA) or not (no SKOA). BMI was measured (kg/m 2 ). Radiographic KOA (RKOA) was assessed according to Ahlbäck criteria (1-5), defined as RKOA with grade 1 or more in at least one knee. Prevalence was calculated (frequencies, %) for each criterion, and Chi-Square test or the Independent-Samples t-test were used for comparisons between individuals fulfilling SKOA or not. Results: The mean age was 52 (min-max 24-73) years, 70% were women and 22% were classified with RKOA. The prevalence of SKOA according to each criterion was 57% (ACR), 51% (EULAR) and 73% (NICE) respectively. In total, 48% had SKOA according to all three criteria and whereof 32% had RKOA, compared to 10% RKOA among individuals with no SKOA. Regardless of the criterion, significantly more individuals classified with SKOA also had RKOA compared to individuals with no SKOA, p&lt;0.001. Those classified as SKOA were significantly older and had higher BMI compared with no SKOA (Table 1). Conclusion: Approximately 50-70% of the individuals with knee pain were classified as having SKOA, where EULAR criteria had the lowest prevalence. A better understanding of early knee pain classification according to different clinical criteria is essential for the ability to capture and follow the long-term prognosis of early SKOA. Further longitudinal studies are needed. References: [1]Altman R et al. Arthritis Rheum. 1986;29(8):1039-49. [2]Zhang W et al. Ann Rheum Dis. 2010;69(3):483-9. [3]Health NIf, Excellence C. UK: National Institute for Clinical Excellence. 2014. Table 1. Comparisons between the ACR, EULAR and NICE criteria of symptomatic knee osteoarthritis, stratified for symptomatic knee osteoarthritis or not ACR EULAR NICE Total OA No OA P-value OA No OA P-value OA No OA P-value N (% ) 296 (100) 170 (57.4) 98 (33.1) 152 (51.4) 114 (38.5) 215 (72.6) 58 (19.6) Age (Y), Mean (SD ) 51.6 (8.7) 53.3 (7.0) 49.0 (10.3) &lt;0.001 54.5 (5.1) 48.1 (10.8) &lt;0.001 54.7 (4.9) 40.5 (9.8) &lt;0.001 Gender , female (% ) 208 (70.3) 121 (71.2) 66 (67.3) 0.511 108 (58.4) 77 (67.5) 0.538 154 (71.6) 36 (62.1) 0.160 BMI (kg/m 2 ), Mean (SD ) 26.4 (4.6) 26.5 (4.5) 25.8 (4.3) 0.179 26.9 (4.5) 25.4 (4.2) 0.005 26.7 (4.5) 24.8 (3.8) 0.004 RKOA , n (% ) 64 (21.6) 45 (26.5) 12 (12.2) 0.003 47 (30.9) 10 (8.7) &lt;0.001 58 (27.0) 1 (1.7) &lt;0.001 Independent-samples t-test and Chi-2-test. Bold =Significant correlation (p≤0.05). OA = Osteoarthritis. ACR = American College of Rheumatology. EULAR = the European League Against Rheumatism. NICE = the National Institute of Care and Excellence. BMI = Body Mass Index. RKOA = Radiographic Knee Osteoarthritis (Ahlbäck, with grade ≥1 in ≥1 knee). Disclosure of Interests: None declared.