Immunoglobulin subclass 4 for the diagnosis of immunoglobulin subclass 4-associated diseases in an unselected liver and pancreas clinic population.
OBJECTIVE
The diagnosis of autoimmune pancreatitis (AIP) and immunoglobulin subclass 4 (IgG(4) )-associated cholangitis (IAC) is based on imaging studies, serology, histology and a response to steroid therapy. The major serological finding is an elevation of the serum IgG(4) concentration. Previous studies have shown that its sensitivity is about 70% and its specificity exceeds 90% at a cut-off of 140 mg/dl in selected patient populations. The aim of the present study was to assess the performance of serum IgG(4) as a diagnostic parameter in an unselected liver and pancreas clinic population.


RESULTS
IgG(4) was prospectively determined in 1412 patients and clinical diagnoses were recorded from a review of patient charts. The prevalence of AIP or IAC in the entire cohort was 1.1% (n= 15). The sensitivity of IgG(4) for the diagnosis of AIP and IAC was 80% and the specificity was 86% at a cut-off value of ≥135 mg/dl. The positive predictive value and the negative predictive value were 6% and 99.7%, respectively. The most common differential diagnosis in patients with elevated IgG(4) was liver cirrhosis.


CONCLUSIONS
IgG(4) has a reasonable sensitivity and specificity in a liver and pancreas clinic population, where liver cirrhosis appears to be the most frequent differential diagnosis for elevated IgG(4) concentrations.
Department of Medicine II-Gastroenterology and Hepatology, Medical University of Innsbruck, Anichstrasse 35, Innsbruck, Austria.
Livia
L
Dorn
Armin
A
Finkenstedt
Melanie
M
Schranz
Wolfgang
W
Prokop
Andrea
A
Griesmacher
Wolfgang
W
Vogel
Heinz
H
Zoller
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001317:Austria; D001327:Autoimmune Diseases / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D015415:Biomarkers / Q000097:blood; D016009:Chi-Square Distribution; D002761:Cholangitis / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000145:classification; D008103:Liver Cirrhosis / Q000175:diagnosis / Q000276:immunology; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010195:Pancreatitis / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D015854:Up-Regulation; D055815:Young Adult
D015415:Biomarkers; D007074:Immunoglobulin G