Diagnosing IgG4-RD: Why Classification Criteria Are Not Diagnostic Criteria

"Diagnosing IgG4-RD: Why Classification Criteria Are Not Diagnostic Criteria" takes up the question of how clinicians reach a confident diagnosis without a definitive test.

Dr. Della Torre argues that IgG4-related disease, like most immune-mediated diseases, lacks true diagnostic criteria. He has been misled by mimics, especially rare malignancies that show typical IgG4 features at diagnosis and later prove malignant. He therefore integrates clinical experience, radiologic findings, serology, and pathology. Whenever possible, he obtains tissue to rule out mimics. Pancreatic involvement is the exception, where he considers organ-specific criteria nearly perfect. He relies on them about 98% of the time.

Dr. Katz agrees that no criteria should be used diagnostically in practice. The cause of the disease is unknown, and no test is always positive in patients and negative in others. He considers the classification criteria the closest available tool, but stresses that they are not diagnostic. They were designed to prioritize specificity over sensitivity. Many patients with the disease will not fulfill them because they lack enough points or a safe biopsy site. Others had biopsies after prednisone that were less diagnostic.

Patients can fulfill the criteria without having the disease, Dr. Katz notes, though the reverse is far more common. He finds the exclusion criteria most useful because they list atypical features that should prompt reconsideration. The point weights show how specific each finding is. Autoimmune pancreatitis with biliary involvement alone earns 19 points against a 20-point threshold. Dr. Culver adds that burnt-out pancreatic disease may not meet criteria despite true disease.

On referral, Dr. Katz says someone must manage the disease as a whole, supported by a multidisciplinary team. In the United States, rheumatologists treat most systemic disease. Gastroenterologists often manage exclusively pancreatobiliary disease well, although he still advocates rheumatology input to catch extrapancreatic involvement. Conversely, rheumatologists rely on colleagues for exocrine insufficiency and for surgical options in retroperitoneal fibrosis with ureteral obstruction.

In "Quality of Life in IgG4-RD: Disease, Damage, and Fear of Relapse," the panel will look beyond organ involvement to the lived experience of patients, including treatment burden and the fear of relapse.