<h3>Background</h3> Patients with inflammatory joint conditions have a high prevalence of comorbidities including chronic kidney disease (CKD) [1]. The data pertaining to CKD in rheumatoid arthritis (RA) is limited [2], however and its association with psoriatic arthritis (PsA) remains unclear. Renal disease in RA and PsA is clinically important as it can lead to restrictions in the management of the primary disease, and is also associated with increased all-cause morbidity and mortality [3]. <h3>Objectives</h3> To determine and compare the rate of incident CKD in patients with rheumatoid and psoriatic arthritis and to determine the rate of estimated glomerular filtration rate (eGFR) change over time. <h3>Methods</h3> Patients with RA and PsA who were first diagnosed between 1st January 2005 and 31st December 2010 were included in this retrospective, longitudinal analysis. All eGFR values, calculated using the Modification of Diet in Renal Disease equation, for each patient were collected from time of diagnosis until 31<sup>st</sup> December 2020. Demographic details, disease-specific characteristics, the presence of cardiovascular disease at baseline and anti-rheumatic drug use at each appointment were recorded. Generalized additive models (GAMs) were used to smooth the eGFR trajectories for each patient, and mixed-effects models were then used to estimate crude linear trends in eGFR across the period of observation. The primary outcome measure was diagnosis of CKD, defined as patient's eGFR falling below 60ml/min/m 2 for a period of at least 90 days in their smoothed eGFR trajectory. <h3>Results</h3> The patient sample (n = 159) included 114 RA and 45 PSA patients. RA patients were less likely to be male (39 vs 51%, p = 0.2) and older (mean age at baseline 52 vs 46 years, p < 0.001) than PsA patients. They also tended to have moderately lower eGFR upon initial observation (78 vs 83 ml/min/m2, p = 0.07). Baseline comorbidity profiles were broadly similar between the two groups. Treatment profiles were also similar, but with RA patients prescribed DMARDs at 69% of their appointments on average vs 56% in PSA patients (p = 0.003). There were 22 incident cases of CKD in the RA patients (19%), vs 7 in the PSA patients (16%, p = 0.6), and 17 RA patients died during the observation period (15%) vs 2 PSA patients (4.4%, p = 0.07). Results from a sex- and age-adjusted mixed effects models suggested that eGFR trajectories tended to slowly decline on average in PSA patients (-0.22 ml/min/m2 per year, p vs no trend = 0.14), but increased on average (0.79 ml/min/m2 per year) among RA patients (p for interaction < 0.001). <h3>Conclusion</h3> Incident CKD diagnosis was high in both patient populations. While rate of eGFR decline was greater in patients with PsA, overall rates of CKD diagnosis did not differ significantly. Monitoring of kidney function should be an important part of management of inflammatory joint conditions, as the majority of these patients non-steroidal inflammatory drugs and immunosuppressive therapies which may be contraindicated or require dose adjustment if renal impairment is present. <h3>References</h3> [1] Ziade, N., El Khoury, B., Zoghbi, M. et al. Prevalence and pattern of comorbidities in chronic rheumatic and musculoskeletal diseases: the COMORD study. Sci Rep 10, 7683 (2020). https://doi.org/10.1038/s41598-020-64732-8 [2] Raksasuk S, Ungprasert P. Patients with rheumatoid arthritis have an increased risk of incident chronic kidney disease: a systematic review and meta-analysis of cohort studies. Int Urol Nephrol. 2020 Jan;52(1):147-154. doi: 10.1007/s11255-019-02346-4. Epub 2019 Dec 9. PMID: 31820358. [3] GBD Chronic Kidney Disease Collaboration. Global, regional, and national burden of chronic kidney disease, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017. Lancet. 2020 Feb 29;395(10225):709-733. doi: 10.1016/S0140-6736(20)30045-3. Epub 2020 Feb 13. PMID: 32061315; PMCID: PMC7049905 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.
