Application of the Monoclonal Autoantibody and Its Target Protein Derived from the Peripheral Blood of SLE Patients in Serological Diagnosis and Differential Diagnosis of SLE

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder with limited reliable diagnostic biomarkers. This study evaluates the utility of DEAD-box helicase 5 (DDX5) as a diagnostic and differential marker for SLE and assesses the performance of a capture bead-based flow cytometry (CBFCM) method for detecting serum proteins. Serum samples were collected from 52 patients with SLE, 38 patients with rheumatoid arthritis (RA), 49 patients with lung cancer (LC), and 50 healthy controls (HCs). Levels of DDX5, anti-DDX5, anti-dsDNA, and anti-Sm were quantified using enzyme-linked immunosorbent assay (ELISA) and CBFCM. Serum DDX5 levels were significantly elevated in patients with SLE compared to patients with RA and HCs, correlating with the SLE activity. DDX5 demonstrated strong discriminatory power between SLE and RA. Combining DDX5, anti-dsDNA, and anti-Sm as biomarkers yielded an area under the curve (AUC) of 0.976 for SLE diagnosis. Decision curve analysis indicated a high clinical benefit from the combined biomarkers. The sensitivity and specificity of DDX5 were 66.11% and 88.89% for ELISA, and 72% and 91.3% for CBFCM. DDX5 shows promise as a novel serological biomarker for SLE diagnosis and differential diagnosis. Additionally, CBFCM outperforms ELISA in detecting soluble serum proteins.