Pitfalls of autoimmune serological markers and practical diagnostic workflows in connective tissue diseases and rheumatoid arthritis

Laboratory markers represent a highly valuable tool to support the diagnosis of systemic autoimmune diseases. However, their correct interpretation is essential to avoid misdiagnoses, with particular attention to the most common errors in their clinical use. It is also crucial for clinicians to understand when serological autoimmune markers should be requested, in order to reduce unnecessary, inappropriate, or costly testing for the healthcare system. A diagnostic approach based on the formulation of the right clinical questions is necessary to ensure the appropriate use of immunological markers. This review focuses on the most commonly used and requested autoimmune markers, with particular emphasis on connective tissue diseases and rheumatoid arthritis. Furthermore, common pitfalls and a diagnostic workflow are proposed to assist clinicians in the evaluation of patients with suspected systemic autoimmune diseases.