POS0395 CLASSIFICATION CRITERIA OF JOINT ACTIVITY FOR PATIENTS WITH RHEUMATOID ARTHRITIS USING JOINT INDEX VECTOR
Authors: I. Yoshii, S. Nishiyama
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> A Joint Index Vector (JIV) was developed by Nishiyama, which evaluates only joint involvement in the whole body of the patient with rheumatoid arthritis (RA), presenting a 3-dimensional coordinate axis. This index is available due to a strong correlation with disease activity, functional ability, and pain status[1,2]. However, no useful classification criteria were developed. <h3>Objectives:</h3> In order to evaluate the validity of the newly developed classification criteria of JIV. <h3>Methods:</h3> The materials were RA patients who consulted and measured joint involvement and were interviewed. Referring to a clinical disease activity index (CDAI) and a Health Assessment Questionnaire Disability Index (HAQ-DI), the classification of JIV status was undergone using receiver operating characteristics (ROC). JIV consists of 3 components: the Vx on the x-axis represents the upper extremities affect ratio, the Vy on the y-axis represents the lower extremities affect ratio, and the Vz on the z-axis represents the large joint minus small joint affect ratio. The Vxy is a square root of the sum of Vx squared plus Vy squared. Therefore, the xy-axes coordinates of JIV with which a magnitude of joint involvement was represented and Vxy, the z-axis coordinate of JIV with which the predominant joint of large/small joints was represented, were analyzed regarding CDAI classification criteria or HAQ-DI remission criteria to determine the cutoff index (COI). The ANOVA T-test of CDAI and HAQ-DI was performed to prove COI as a threshold for classification in separating with the COI. When one threshold was determined, these procedures were repeated after the matched cases were excluded. After determining all the criteria thresholds, an evaluation was tested using the open dataset of the National Database of Rheumatic Diseases in Japan (NinJa) in 2015 to evaluate the validity of the classification criteria of the JIV. <h3>Results:</h3> A total of 617 patients were tested for developing the JIV classification criteria. Criteria were determined as Vxy&lt;0.1 as remission (REM), 0.45≥Vxy≥0.1 and 0.125≥Vz as low joint activity (LJA), 0.45&gt;Vxy≥0.1 and Vz&gt;0.125, or 1.0≥Vxy≥0.45 as moderate joint activity (MJA), and Vxy&gt;1.0 as high joint activity (HJA) (Figure 1). In the 11013 cases of the NinJa 2015 dataset, there are 5135 in REM, 2337 in LJA, 3078 in MJA, and 463 in HJA. The SDAI scores in the REM, LJA, MJA, and HJA were 25.8±12.5, 11.0±5.8, 6.8±3.8, and 2.8±2.7, respectively (p&lt;0.0001). The HAQ scores in the REM, LJA, MJA, and HJA were 1.315±0.844, 0.903±0.844, 0.571±0.730, and 0.418±0.698, respectively (p&lt;0.0001) (Figure 2). <h3>Conclusion:</h3> The classification criteria of the JIV are strongly suggested as appropriate and widely available for evaluating not only joint status but also disease activity and functional ability of RA patients. <h3>REFERENCES:</h3> [1] AB0214 Yoshii I, Nishiyama S. DOI: 10.1136/annrheumdis-2023-eular.858. [2] AB0215 Yoshii I, Nishiyama S. DOI: 10.1136/annrheumdis-2023-eular.1069. <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>