Combination of cytoplasmic and nuclear patterns on Hep-2 antinuclear antibody is useful as a screening test for anti-synthetase syndrome.

OBJECTIVE: This study aimed to establish a screening model for differentiating anti-synthetase syndrome (ASS) from other antinuclear antibody (ANA)-associated rheumatic diseases (AARD) using a combination of cytoplasmic and non-cytoplasmic ANA (ncANA) patterns.

METHODS: This retrospective observational study included patients with AARDs such as systemic lupus erythematosus (SLE), systemic sclerosis (SSc), Sjögren's syndrome (SS), mixed connective tissue disease (MCTD), and polymyositis/dermatomyositis (PM/DM) who underwent ANA screening between April 2012 and December 2021. Variables included age, sex, ANA patterns (Cytoplasmic and ncANA), and titers. Logistic regression analysis of Cytoplasmic and ncANA patterns was performed to differentiate ASS from other AARDs.

RESULT: The 981 diagnosed cases of AARDs consisted of SS (n = 451), SSc (n = 264), SLE (n = 201), PM/DM (n = 104), MCTD (n = 52), and ASS, including PM/DM (n = 64). Of these, 155 patients had ≥2 overlapping diseases; however, there was no overlap between AARDs and ASS. ASS is more likely to occur when the cytoplasmic titer is positive and the ncANA <320. Receiver operating characteristic (ROC) analysis of the Cytoplasmic and ncANA range revealed an area under the ROC curve (AUC) of 0.885 (95% CI: 0.844 to 0.927).

CONCLUSION: It is important to detect cytoplasmic patterns as an ANA screening test for ASS diagnosis, even if the titer is low. Additionally, combining the cytoplasmic and ncANA patterns yields more accurate ASS screening results.