Rate of Decrease in Serum Autotaxin Can Predict Relapse of Type 1 Autoimmune Pancreatitis After Initial Steroid Therapy

Abstract

Abstract Objectives: IgG4 has been reported as a predictive marker of relapse in autoimmune pancreatitis (AIP). Serum autotaxin (ATX) was also recently found to associate with AIP relapse. This study examined the changes in serum IgG4 and ATX levels for predicting relapse in AIP patients after initial steroid therapy. Methods: Patients with AIP who had received initial steroid therapy were retrospectively enrolled. Serum IgG4 and ATX levels were measured before and after treatment. The rates of decrease (Δ) in serum marker levels were calculated by dividing the difference between before and after steroid therapy by the number of days between them. Results: The 37 AIP patients analyzed included 26 non-relapse and 11 relapse patients. The median Δ of serum IgG4 was 5.19 (interquartile range [IQR]: 2.65-14.49) in the non-relapse group and statistically comparable to the 3.07 (IQR: 1.79-4.43) in the relapse group (P=0.12). The median Δ of serum ATX was 1.32×10-3 (IQR: 0.23×10-3-2.45×10-3) in the non-relapse group and 0.58×10-3 (IQR: -1.34×10-3-0.91×10-3) in the relapse group, which was a significant difference (P<0.01). Positive predictive values (PPVs) for relapse were 70.1% for the Δ of IgG4 and 67.6% for the Δ of ATX. The PPV at either the Δ of IgG4 or the Δ ATX cut-off was 86.5%. In the 10 cases of IgG4 <270 mg/dL, the PPV for the Δ of IgG4 was 20%, while that for the Δ of ATX was 70%. Conclusions: The combination of IgG4 and ATX decrease rates may help predict relapse in AIP patients after steroid therapy.