Aim: to choose the optimal method for determining glomerular filtration rate (GFR) for assessing the severity of renal failure in patients with rheumatoid arthritis (RA), depending on the clinical and laboratory variants of the disease course. Patients and Methods: an open cross-sectional study was conducted with the participation of 96 subjects with a reliable diagnosis of RA (mean age 54.4±11.6 years, disease duration 10.7±8.56 years, 57.3% — with moderate RA activity, 50.0% — with a developed clinical stage, 38.5% — with metabolic syndrome (MS)). For a comparative assessment of renal function, the estimated glomerular filtration rate (eGFR) was used according to the CKD-EPI formulas based on creatinine (eGFRcr), on cystatin C (eGFRcyst) and on creatinine and cystatin C (eGFRcr-cyst). Results: serum cystatin C positively correlated with RA activity indices according to the DAS28 index (r=0.52, p=0.006), with the erythrocyte sedimentation rate (ESR) (r=0.4, p=0.041), C-reactive protein (CRP) levels (r=0.48, p=0.012) and serum creatinine (r=0.55, p=0.003). Elevated cystatin C values in patients with RA were associated with high disease activity (p<0.001) and the severity of MS (p<0.001). The comparison of eGFR indicators showed significant differences when using the selected methods (χ2=9.91, p=0.007). Decrement of GFR according to eGFRcr data (compared to the indicators of eGFRcr-cyst or eGFRcyst) was observed in 11–18% of the patients with RA and high / optimal renal function (> 90 mL/min/1.73 m2) and approximately 10% of patients with RA with slightly reduced GFR (60–89 mL/min/1.73 m2). Regression analysis methods revealed an association between eGFRcyst and CRP (p<0.001), ESR (p=0.007), the DAS28 index (p<0.001), BMI (p<0.001), waist measurement (p=0.005); between eGFRcr-cyst and CRP (p<0.001), BMI (p<0.001); between eGFRcr and CRP (р=0.013), Hb level (р=0.029). Two-way analysis of variance demonstrated the effect of inflammatory (p<0.001) and metabolic (p=0.006) disorders on eGFRcyst (R2=0.34, р<0.001). Conclusion: the use of the CKD-EPI creatinine equation leads to an overestimation of eGFR in almost 20% of patients with RA. A lower eGFRcyst, in contrast to eGFRcr, is associated with multiple risk factors for chronic kidney disease in terms of parameters not related to renal failure but related to the activity and severity of RA. The eGFRcr-cyst equation may be optimal for patients with RA, regardless of the disease activity and the presence of MS signs. KEYWORDS: rheumatoid arthritis, chronic kidney disease, glomerular filtration rate, creatinine, cystatin C, metabolic syndrome. FOR CITATION: Alexandrov V.A., Alexandrov A.V., Zborovskaya I.A., Alexandrova N.V. Evaluation of renal failure using the results of the serum cystatin C determination of patients with rheumatoid arthritis. Russian Medical Inquiry. 2021;5(5):280–287 (in Russ.). DOI: 10.32364/2587- 6821-2021-5-5-280-287.
Cystatin C and Iris: Advances in the Evaluation of Kidney Function in Critically Ill Dog