TY - JOUR T1 - Clinical Utility of Antipeptidyl Arginine Deiminase Type 4 Antibodies JF - The Journal of Rheumatology JO - J Rheumatol SP - 329 LP - 330 DO - 10.3899/jrheum.180905 VL - 46 IS - 3 AU - ERIKA DARRAH AU - LAURA MARTINEZ-PRAT AU - MICHAEL MAHLER Y1 - 2019/03/01 UR - http://www.jrheum.org/content/46/3/329.abstract N2 - Rheumatoid factor (RF) and anticitrullinated protein antibodies (ACPA) are important biomarkers in the diagnosis of rheumatoid arthritis (RA) but leave a gap of > 50% seronegative in early RA1. In addition, there is marked clinical heterogeneity in the seropositive group, precluding the use of RF and ACPA alone as prognostic biomarkers. These characteristics drive the demand for novel diagnostic and prognostic markers in RA1. In this context, we read the recent paper by Guderud, et al on the clinical utility of antipeptidyl arginine deiminase type 4 (anti-PAD4) antibodies with great interest2. The authors studied anti-PAD4 antibodies in 745 patients with RA using a dissociation-enhanced lanthanide fluorescence immunoassay (DELFIA) and found 26% to be positive. In addition, the study also investigated the genotype of PADI4 using TaqMan assays in 945 patients and 1118 controls. Based on the results, the authors concluded that anti-PAD4 antibodies are not useful clinical biomarkers in RA. Unfortunately, there are some significant questions and concerns regarding this conclusion.Importantly, the authors did not … Address correspondence to M. Mahler, Inova Diagnostics, 9900 Old Grove Road, San Diego, California 32131-1638, USA. E-mail: mmahler{at}inovadx.com or m.mahler.job{at}web.de ER -