Rheumatoid arthritis (RA) is a chronic autoimmune disease with a high potential for disability, where early diagnosis is crucial for timely initiation of disease-modifying antirheumatic drugs (DMARDs) and for improving long-term outcomes. In recent decades, particular attention has been paid to serological biomarkers, among which rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA), including anti-CCP and anti-MCV, play a leading role. These markers not only confirm the diagnosis but also help predict the risk of aggressive disease course and joint erosions. Modern immunoassay methods have significantly expanded diagnostic opportunities. Along with traditional approaches such as latex agglutination, enzyme-linked immunosorbent assay (ELISA), and turbidimetry, innovative technologies are actively being implemented, including electrochemical impedance spectroscopy (EIS), surface-enhanced Raman spectroscopy (SERS), photoelectrochemical biosensors, and microfluidic platforms. Multiplex immunoassays are of particular importance, as they allow the simultaneous detection of multiple biomarkers in a single sample, thereby increasing diagnostic accuracy, facilitating patient stratification, and promoting the principles of personalized medicine. Despite their advantages, multiplex methods face several limitations: the need for highly specific antibody pairs, the risk of cross-reactivity, the lack of standardized reference materials for ACPA, and challenges in quality control. Future development of these technologies depends on assay standardization, implementation of international reference standards, and optimization of diagnostic thresholds. In conclusion, the integration of modern immunoassay techniques and multiplex platforms into clinical practice provides new opportunities for early diagnosis and prognosis of RA, ultimately reducing disability rates and improving patients’ quality of life