Background/Purpose: The entity of interstitial lung disease with autoimmune disease features (ILD-AF) is increasingly gaining traction as condition that is best co-managed by pulmonologists and rheumatologists.  In September 2016, our institution initiated a comprehensive ILD auto-antibody panel, including ANA, RF, CCP, Jo-1, PL-7, PL-12, EJ, OJ, SRP, MDA5, NXP2, Ku, PMSCL, U1RNP, and Scl-70 to assist in the diagnosis of ILD-AF. We compared the number of additional diagnostic studies ordered in patients that had an autoantibody panel ordered to determine if autoantibody panels improve diagnostic yields and/or increase costs.

Methods: In patients that had an autoantibody panel, we assessed whether the test resulted in hand radiographs (XR), creatinine kinase (CK), aldolase, electromyogram (EMG), muscle magnetic resonance imaging (MRI), capillaroscopy, age appropriate cancer screening, and whether a CTD or ILD-AF diagnosis was subsequently given by a comprehensive chart review. We compared the number of tests ordered when a panel was positive versus negative by frequency (descriptive statistics). This project was IRB approved.

Results: In the course of 18 months,170 comprehensive autoantibody panels were ordered. Of these, 100 patients (59%)  had at least one positive autoantibody test. As expected both groups had the same number of  HRCT chest, but the frequency of tests subsequently ordered after a positive vs. negative autoantibody panel are described in Table 1. A diagnosis of CTD or ILD-AF was given in 26% of patients with at least one positive autoantibody test identified on these panels, compared to 3% of patients with negative panels.

Conclusion: In a single center cohort retrospective analysis, positive auto-antibodies identified on ILD-AF panels resulted in more creatine kinase levels, aldolase levels, hand radiographs, and muscle MRIs, but was also more likely to result in a diagnosis of CTD or ILD-AF. In conclusion, a positive auto-antibody panel appears to increase costs by number of tests ordered, but also improves diagnostic yields. The role of capillaroscopy in ILD-AF diagnosis may be important.

Table 1: Tests and diagnostic yield in patients with ILD autoantibody panel