Background/Purpose: One of the most severe visceral manifestations of RA is nephropathy. The key symptoms of renal dysfunction (RD) are microalbuminuria (MA), β-2-microglobulinuria (β-2M), reduced renal blood flow (RBF) and decreased glomerular filtration rate (GFR).

The aim of our study was to examine whether tumor necrosis factor-α (TNFα) can induce and maintain decrease RD and whether this is associated with severity of RA.

Methods: The median age of the group of 35 (28 female, 7 male) participants with early eRA was 50.71 ± 2.25 years, with median disease duration 9.21 ± 0.43 months. TNFα was from ELISA Kits, R&D Systems (USA), MA and β-2M were from ORGenTec GmbH (Germany).The ratio of albumin-creatinine (AB/CR) in the morning portion of urine and the glomerular penetration index (GPI), reflecting the average concentration of AB in the glomerular ultrafiltration, were also calculated by formula: GPI =Р´V/GFR, where P – of excreted AB urine concentration (mg/l); V – minute diuresis (ml / min.). The serum and urine CR concentration was determined by a unified method using the Jaffe color reaction (Popper method).

Results: The severity of tubular damage in early eRA is associated with TNF-α expression, especially in the patients with TNF-α above 250 pg/mL, when MA rates were significantly higher (χ²=12,3 in р<0,01). We identified robust data that patients with high TNFα, the number of reported cases of MA was significantly higher. We evaluated not only the stage but also the nature of the dependence, describing the functional relationship between the numerical variables. We have performed of regression analysis, while the serum range of TNFα was considered as an independent variable and as a dependent variable – index characterizing the severity of RD (index of MA).We identified that in the eRA patients with high TNFα, the number of reported cases of MA was significantly higher (χ2=12,3 with р<0,01). The obtained dependence showed the dynamics of expression of RD in eRA with a progressive deterioration which did associate with the levels of TNFα expression, and variety of the β ‐2M urine rates in the interval 200–350 μg/L.

Conclusion: In this study we have confirmed, that overexpression of TNF-α is involved in the induction of RD, which is manifested by decrease of GFR and increase of urinary excretion of microproteins. At the same time, the dynamics of MA and β‐2M values was reliably determined by the stage of disease activity, which reflects the RA severity.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-between-inflammation-and-changes-in-kidney-function-in-patients-with-early-rheumatoid-arthritis/