Potential utility of anti-DFS70 antibodies to exclude systemic autoimmune rheumatic disease (SARD) in patients with interstitial lung disease (ILD)
23 February 2017 (online)
Anti-DFS70 antibodies, corresponding to the dense fine speckled ANA indirect immunofluorescence pattern in HEp-2 substrates, have been observed in chronic inflammatory conditions, cancers and even in healthy individuals but only in a small percentage of patients with systemic autoimmune rheumatic diseases. These antibodies, if positive in the context of ANA positivity, are considered biomarkers for the exclusion of SARD.
Aim of this study:
To investigate the presence of serum anti-DFS70 antibodies in patients with ILD and a possible correlation with ANA status and the presence or development of SARD.
262 patients with ILD (160 IPF and 102 NSIP), 49 healthy controls (HC) and 34 scleroderma (SSc) patients as negative control were studied. 39 patients (3 IPF and 36 NSIP) developed SARD during a 24 months follow up period. Antinuclear antibody testing was performed by indirect immuno-fluorescence (IIF) on HEp-2 cell substrates and positivity cut off was set at 1:320. Serum anti-DFS70 at baseline was measured by ELISA (MBL Co., Ltd., Japan), and the cut-off for positivity was set at 400 U/ml.
ANA were positive in 51 (32%) IPF patients, 49 (48%) NSIP patients and 29 (85%) SSc patient. All HC were ANA negative but 35% were anti-DFS70 positive. Anti-DFS70 were positive in 31 (19%) IPF patients, 13 (13%) NSIP patients and 2 (6%) SSC patient.
Among 100 ANA(+) ILD patients, 21 (21%) were anti-DFS70 positive. Among 162 ANA(-) ILD patients, 23 (14%) were anti-DFS70 positive. Among the 39 patient who developed SARD during follow-up, 7 (18%) were anti-DFS70 (+) and 32 (82%) were anti-DFS70 (-): 31 of them had NSIP and 1 had IPF.
ANA positivity combined with anti-DFS70 negativity seems to be associated with SARD especially in NSIP patients.