The Japanese diagnostic criteria for autoimmune chronic pancreatitis: is it completely satisfactory?

Autoimmune chronic pancreatitis (AIP) is a very attractive disease to clinicians in terms of its dramatic response to the oral steroid therapy in contrast to ordinary chronic pancreatitis. In the year 2002, the Japan Pancreas Society published the diagnostic criteria of AIP, and many clinicians around the world use these criteria for its diagnosis. The purpose of this study was to evaluate whether the Japanese criteria for the diagnosis of AIP are adequate or not.

We retrospectively analyzed the clinical, radiologic, laboratory, and histologic features of 31 patients with AIP who have been successfully treated with oral corticosteroid. All the enrolled patients showed normalization or marked improvement in symptoms, laboratory, and imaging findings after steroid treatment.

The mean patients' age was 56 years (range, 32-78 years) and comprised 25 males and 6 females. Seven patients who responded to the steroid did not satisfy the Japanese imaging criterion because the extent of irregular narrowing was less than one third of the entire length of main pancreatic duct. Among these 7 patients, 1 patient did not meet the laboratory and histopathologic criteria as well. Another 2 patients fulfilled the Japanese imaging criterion only and showed normal IgG level, negative results of autoantibody measurements, and nondiagnostic pancreatic histopathology. Taken together, 9 (29%) of the 31 patients did not meet the Japanese diagnostic criteria for AIP, yet responded to the steroid.

Clinicians may miss a substantial portion of AIP patients who may benefit from steroid therapy when the diagnosis is confined to those who satisfy the criteria proposed by the Japan Pancreas Society. It is necessary to convene a worldwide consensus to develop an improved diagnostic criteria for AIP.