The median (range) follow-up was 19.0 (0.5-62.1) months after initial presentation and 16.8 (0.0-46.1) months after initiation of treatment. Serum concentrations of IgG subclass 4 were measured by automated nephelometry (Behring Nephelometer II; Dade Behring,

Newark, DE).12 Tissue immunostaining using monoclonal antihuman IgG4 antibody was performed as reported.3 AUY-922 in vivo The number of IgG4-positive plasma cells per high-power field (hpf) was counted in each specimen (Nikon E 600, field diameter 0.625 mm; Nikon, Tokyo, Japan). Moderate (11-30 cells/hpf) to severe (>30 cells/hpf) infiltration with IgG4-positive cells in the presence of characteristic histology was considered diagnostic of AIP. Scores were assigned as negative (0-1) or positive.2, 3 All histologic specimens were reviewed by a single pathologist (L.Z.). IAC was diagnosed histologically from a resection specimen or core biopsy if there was a lymphoplasmacytic infiltrate within and around bile ducts with associated obliterative phlebitis and storiform fibrosis leading to sclerosis of the bile duct.25-27 EPZ-6438 Available cholangiograms, computerized tomography,

magnetic resonance imaging, and magnetic resonance cholangiopancreatography scans from the 31 patients with CCA-PSC in the test cohort were reviewed by a single radiologist (N.T.) for features of AIP. Data were analyzed using JMP v. 8.0.0 (SAS Institute, Cary, NC). Differences between groups were evaluated using the chi-square or Fisher’s exact test for qualitative variables and the rank sum test for quantitative variables. Receiver operator characteristic (ROC) curves were used to judge the diagnostic utility of sIgG4

levels. IgG4 values (mg/dL) are represented as median and interquartile range, and a two-tailed P value of less than 0.05 was considered significant. Spearman’s correlation coefficient analysis was used to determine the relationship between CA19-9 and sIgG4 level in CCA patients. Survival of CCA patients was defined as the time from diagnosis to death or last follow-up visit date. Median survival of CCA patients with elevated IgG4 > upper limit of normal (ULN) was compared Phosphatidylethanolamine N-methyltransferase to that of CCA patients with normal sIgG4 levels by the Kaplan-Meier method. For the test cohort, we used frozen serum collected at the time of diagnosis from 126 patients with CCA (82 hilar or extrahepatic CCA and 44 intrahepatic CCA). We compared the sIgG4 level and other clinical and laboratory characteristics in these patients to those of 50 patients with known IAC. As expected, the median sIgG4 levels in the 50 IAC patients were significantly higher than the levels in the 126 patients with CCA (irrespective of PSC status) (261.0 mg/dL vs 37.5 mg/dL, P < 0.0001, rank sum test) (Table 1A). The individual sIgG4 levels in each group are shown in the scatterplot (Fig. 2).