ASSESSMENT OF THE SWOLLEN TO TENDER JOINT COUNT RATIO AS A PREDICTOR OF RESPONSE IN RHEUMATOID ARTHRITIS PATIENTS: A COHORT STUDY

Background: Several response predictors have already been studied in rheumatoid arthritis, especially since the introduction of biological therapies. The swollen to tender joint count ratio (STR) has been proposed as a predictor of response in patients receiving anti-TNF therapy, but its usefulness in other therapies is not yet well established. Objectives: To assess whether STR can be a predictor of response in patients with rheumatoid arthritis under b/tsDMARD. Methods: Longitudinal and retrospective study that included patients diagnosed with rheumatoid arthritis followed in the Rheumatology Department of a tertiary hospital, under therapy with b/tsDMARD. Demographic, laboratory, and clinical data were collected, including tender and swollen joint counts (as included in DAS 28), Visual Analog Scale (VAS), DAS28 4V, SDAI, CDAI, ACR and EULAR responses, and HAQ. All patients were evaluated at 0, 6 and 12 months after starting the first b/tsDMARD therapy performed after 2015. The variation in each parameter compared to baseline was calculated at 6 and 12 months and represented as a delta. A cutoff of 1 was defined for comparison between STR groups. The correlations between the continuous variables were assessed by Pearson’s test and comparison between groups of ratios using t test (continuous variables) and chi-square test (categorical variables). Multiple linear regression and multivariate logistic regression were performed to determine response predictors. Results: A total of 287 patients were included, 238 (82.9%) females, aged 55.7±10.8 years and diagnosed with rheumatoid arthritis for 11.2±8.1 years. Two hundred and sixty-nine (93.7%) were on csDMARD; with regard to b/tsDMARD therapy, 66 started etanercept (23.0%), 62 tocilizumab (21.6%), 58 rituximab (20.2%), 44 adalimumab (15.3%), 17 golimumab (5.9%), 14 abatacept (4.9%), 7 certolizumab (2.4%), 5 upadacitinib and baricitinib (1.7%), 4 infliximab (1.4%), 3 tofacitinib (1.0%), and 2 anakinra (0.7%). At the start of therapy with b/tsDMARD, the mean DAS28 4V was 4.7±1.5, CDAI 20.4±12.2, SDAI 22.8±16.4, erythrocyte sedimentation rate 31.8±24.4, C-reactive protein (CRP) 1.5±1.7, patient VAS 62.6±1.5, physician VAS 41.4±29.7, pain VAS 62.5±24.8, and HAQ 1.5±0.6; median tender joint count was 4 (interquartile range - IQR - 6), swollen joint count was 3 (IQR 6), and STR joint count was 0.9 (IQR 0.5). When the STR < 1 and STR ≥1 groups were compared, it was found that there were no differences in these variables when starting b/tsDMARD, nor in the therapies they performed. At 6 months, the STR ≥1 group showed a higher proportion of patients in CDAI remission (CDAI ≤2.8 – 15.3% vs 6.9%, p=0.033) and in DAS28 4V remission or low disease activity according to DAS28 4V (DAS28 4V ≤3.2 – 36.5% vs 22.4%, p=0.008). At 12 months, the STR ≥1 group exhibited less disease activity (mean DAS28 4V 3.2±1.2 vs 3.6±1.3, p=0.028) and a higher proportion of patients in DAS28 4V remission (25.2% vs 19.7%, p=0.047). No significant differences were found between the groups in the other variables studied. In the correlation studies, a weak correlation was identified between STR and CRP at 12 months (r=0,28, p<0,001). In multiple linear regression studies, when adjusted for sex, age, prednisolone, csDMARD, inflammatory parameters, b/tsDMARD, STR was not shown to be a predictor of DAS28 4V disease activity at 1 year; in multivariate logistic regression studies, when adjusted for the same variables previously described, STR was not shown to be a predictor of remission or remission or low disease activity according to DAS28 4V at 1 year. Conclusion: The STR is a practical, easy-to-use index that can be used as an adjunct in clinical practice in the evaluation of patients with rheumatoid arthritis, as it is associated with a better response to b/tsDMARD therapy, regardless of patient status and therapy, although it should not be used alone, as it does not appear to be a predictor of response, according to the indices that are currently used. REFERENCES: [1]Kristensen LE et al. Arthritis Care Res (Hoboken). 2014 Feb;66(2):173-9. Disclosure of Interests: None declared. Citation: , volume 81, supplement 1, year 2022, page 545Session: Rheumatoid arthritis - prognosis, predictors and outcome (POSTERS only)