Serum free light chain assessment in type 1 autoimmune pancreatitis

Abstract

Background: /Object: Some patients with type 1 autoimmune pancreatitis (AIP), the pancreatic manifestation of IgG4-related disease, have normal serum IgG4. The aim of this study is to investigate the diagnostic value of measuring serum free light chains (FLCs) in type 1 AIP.

Materials and methods: Thirty-seven patients with type 1 AIP, and 21 healthy, 17 alcoholic chronic pancreatitis (ACP), 21 idiopathic chronic pancreatitis (ICP) and 20 pancreatic cancer (PC) patients were enrolled. Serum IgG4 and FLC concentrations were measured using sFLC Freelite assays on a nephelometric analyzer.

Results: Active AIP patients have significantly higher serum levels of κ (median 30.97 (12.3-227.0) mg/L) and λFLC (median 20.53 (12.36-102.7) mg/L)) than healthy controls (κFLC; median 12.5 (3.1-52.1) mg/L), λFLC: median 12.45 (5.4-39.5) mg/L) (p < 0.05) correlating with raised serum IgG4, and significantly higher summated FLCs (∑) (median 53.09 (25.0-218.0) mg/L) than ICP patients (median 26.77 (15.0-89.2) mg/L) and healthy controls (median 24.43 (8.5-91.6) mg/L) (p < 0.05). AIP patients (median 1.43 (0.84-3.24)) showed significantly higher κ/λ ratios than ACP (median 0.83 (0.42-1.18)), ICP (median 0.87 (0.47-2.16)), PC patients (median 0.90 (0.48-1.27)) and healthy controls (median 0.963 (0.51-1.32)). There was a correlation between increased κ and λ FLCs levels and the number of affected organs involved in IgG4 related disease.

Conclusion: Patients with type 1 AIP have increased serum k and λ FLC concentrations, Σ FLC, and κ/λ ratios. These novel biomarkers may be useful in the diagnosis of type 1 AIP and in monitoring disease activity.

Keywords: Autoimmune pancreatitis; Free light chain; IgG4-related disease.