Diagnostic performance of antibodies against extractable nuclear antigens detected by immunoblot in the differentiation of connective tissue diseases.

Connective tissue diseases are inflammatory, autoimmune diseases that threaten the quality of life. To evaluate the differential diagnostic performance of antibodies against extractable nuclear antigens (ENAs) detected by immunoblot in patients with connective tissue diseases. An observational, descriptive, and cross-sectional study was conducted at the Immunoserology Service of the Arzobispo Loayza National Hospital and the Pharmacology Laboratory of the Faculty of Medicine at the National University of San Marcos between June 2020 and March 2021. The medical records of 300 patients with connective tissue disease were reviewed, and the immunoblot method was used to detect antibodies against ENA in the patients' serum. Final diagnoses were established according to classification criteria predefined by the EULAR/ACR (European Alliance of Associations for Rheumatology/American College of Rheumatology). Of the 300 cases with connective tissue disease, 87 (29%) cases had systemic lupus erythematosus, and 51 cases had anti-dsDNA with sensitivity of 59%, specificity of 87%, PPV of 65%, NPV of 84%, LR+ of 4.62, and LR- of 0.47 in SLE. In 81 (27%) cases of Sjögren's syndrome, 68 had anti-Ro 52 with sensitivity of 83%, specificity of 68%, PPV of 49%, NPV of 91.4%, LR+ of 2.59, and LR- of 0.25. It was demonstrated in 35 (11.7%) cases of CREST: 31 cases had anti-Cenp B with sensitivity of 88%, specificity of 96%, PPV of 77%, NPV of 98% and LR+ of 22. Selected profiles of antibodies against ENAs detected by immunoblot can support the differential diagnosis of connective tissue diseases.