INDICATORS OF BONE METABOLISM IN PATIENTS WITH RHEUMATOID ARTHRITIS WITH IMPAIRED BONE MINERAL DENSITY: CHARACTERISTICS, THEIR FEATURES AND DIAGNOSTIC VALUE.

Rheumatoid arthritis (RA) is an autoimmune disease with a chronic inflammatory process that affects bone metabolism and leading to impaired bone mineral density (BMD). Therefore, the determination of laboratory markers of bone metabolism contributes to a better understanding of the pathogenesis of metabolic bone diseases. The aim of the study - to characterize the bone metabolism parameters in rheumatoid arthritis patients with impaired bone mineral density, to find out their features and diagnostic value. The study included 76 patients randomly stratified by RA status who were treated in the Rheumatology Department of Lviv Regional Clinical Hospital, a municipal non-profit enterprise of Lviv Regional Council, from 2013 to 2019. The goal was achieved by performing three consecutive stages of the study. At the first stage, markers of bone formation and bone resorption were characterized. At the second stage, the peculiarities of these indicators were determined. The third stage was to determine the diagnostic value of the content of the markers of OCN formation, P1NP and resorption marker β-CrossLaps. According to the results of the study at the first stage, it was found that, in RA patients with osteopenia, the serum content of markers of osteoblastic bone function OCN (p=0.000) and P1NP (p=0.035) was significantly lower compared to the healthy individuals of CG, while the content of the marker of bone resorption β-CrossLaps was significantly higher (p=0. 021); in RA patients with OP, the serum content of both markers of osteoblastic bone function OCN (p=0.000) and P1NP (p=0.001) is significantly lower, while β-CrossLaps (p>0.050) is only slightly higher compared to healthy CG subjects. According to the results obtained at the second stage of the study, it can be stated that the content of OCN and P1NP in the blood serum is significantly lower in RA patients both with osteopenia and OP compared to RA patients without BMD disorders. At the third stage of the study, it was found significant relationship between the content of P1NP and belonging to SG1 (AC -0.52). A confirmed relationship was found between the content of OCN and belonging to the group with OP (direct direction of AC 0.57; p=0.017). Bone structure disorders in rheumatoid arthritis patients with osteopenia are characterized by a weakening of bone formation and increased resorption processes; in rheumatoid arthritis patients with osteoporosis, the weakening of osteoblastic bone function is more pronounced compared to rheumatoid arthritis patients with osteopenia. For rheumatoid arthritis patients with unimpaired bone mineral density, the highest diagnostic value is provided by procollagen type I N-terminal propeptide. For rheumatoid arthritis patients with osteoporosis, osteocalcin is a diagnostically valuable marker.