Diagnosis and Treatment of Autoimmune Pancreatitis in China: A Systematic Review

Recent advances in IgG4-related autoimmune pancreatitis

The incidence of IgG4-related autoimmune pancreatitis (IgG4-AIP) is high in Asia and other countries, and unnecessary treatment is often undertaken due to both missed diagnosis and misdiagnosis in clinical practice. Although IgG4-AIP has attracted increasing attention, the details of IgG4-AIP pathogenesis and systemic immune response, including its relationship to tumor pathogenesis, are still unclear. In recent years, research on serum immunological detection, pathological features, clinical manifestations, diagnosis and treatment measures for IgG4-AIP has gradually increased. It is of great importance to summarize and discuss the latest progress regarding IgG4-AIP disease.

Type 1 Autoimmune Pancreatitis in Europe: Clinical Profile and Response to Treatment

BACKGROUND & AIMS

Autoimmune pancreatitis (AIP) is an immune-mediated disease of the pancreas with distinct pathophysiology and manifestations. Our aims were to characterize type 1 AIP in a large pan-European cohort and study the effectiveness of current treatment regimens.

METHODS

We retrospectively analyzed adults diagnosed since 2005 with type 1 or not-otherwise-specified AIP in 42 European university hospitals. Type 1 AIP was uniformly diagnosed using specific diagnostic criteria. Patients with type 2 AIP and those who had undergone pancreatic surgery were excluded. The primary end point was complete remission, defined as the absence of clinical symptoms and resolution of the index radiologic pancreatic abnormalities attributed to AIP.

RESULTS

We included 735 individuals with AIP (69% male; median age, 57 years; 85% White). Steroid treatment was started in 634 patients, of whom 9 (1%) were lost to follow-up. The remaining 625 had a 79% (496/625) complete, 18% (111/625) partial, and 97% (607/625) cumulative remission rate, whereas 3% (18/625) did not achieve remission. No treatment was given in 95 patients, who had a 61% complete (58/95), 19% partial (18/95), and 80% cumulative (76/95) spontaneous remission rate. Higher (≥0.4 mg/kg/day) corticosteroid doses were no more effective than lower (<0.4 mg/kg/day) doses (odds ratio, 0.428; 95% confidence interval, 0.054-3.387) and neither was a starting dose duration >2 weeks (odds ratio, 0.908; 95% confidence interval, 0.818-1.009). Elevated IgG4 levels were independently associated with a decreased chance of complete remission (odds ratio, 0.639; 95% confidence interval, 0.427-0.955). Relapse occurred in 30% of patients. Relapses within 6 months of remission induction were independent of the steroid-tapering duration, induction treatment duration, and total cumulative dose.

CONCLUSIONS

Patients with type 1 AIP and elevated IgG4 level may need closer monitoring. For remission induction, a starting dose of 0.4 mg/kg/day for 2 weeks followed by a short taper period seems effective. This study provides no evidence to support more aggressive regimens.

Autoimmune pancreatitis type 2 (idiopathic duct-centric pancreatitis): A comprehensive review

Autoimmune pancreatitis (AIP) is an uncommon fibro-inflammatory disorder precipitated by autoimmune/inflammatory reactions. Currently, there are two clinical subtypes of AIP (type 1 [AIP-1] and type 2 [AIP-2]) that correspond to two histologic descriptors (lymphoplasmacytic sclerosing pancreatitis and idiopathic duct-centric pancreatitis, respectively). While our understanding of AIP-1 has evolved considerably over the years, little is known about AIP-2 due to its rarity, often leading to misdiagnosis, delayed treatment, and even unnecessary surgical resection. Compared to AIP-1, AIP-2 exhibits distinct clinical and histologic features. Because AIP-2 is a pancreas-restricted disease without a specific serum marker, the evaluation of histologic features (e.g., granulocytic epithelial lesions) is essential for an accurate diagnosis. Patients with AIP-2 respond well to glucocorticoids, with anti-tumor necrosis factor-alpha antibodies as a promising alternative therapy. The prognosis of AIP-2 is generally favorable and relapse is uncommon. Here, we provide an overview of our current knowledge on the clinical features, diagnosis, therapeutic regimens, prognosis, and putative mechanisms underlying AIP-2. Notably, the diagnostic differentiation between AIP-2, especially the mass-forming/focal type, and pancreatic cancer is important, but challenging. In this regard, endoscopic ultrasound-guided core biopsy has a key role, but novel diagnostic markers and modalities are clearly needed.

IgG4-related digestive diseases: diagnosis and treatment

IgG4-related digestive diseases encompass a group of chronic inflammatory disorders characterized by autoimmune reactions and fibrosis affecting multiple digestive organs. These diseases are identified by elevated serum levels of IgG4 and the presence of IgG4-positive plasma cell infiltration in the affected sites, along with storiform fibrosis, obliterative phlebitis, and eosinophilic infiltration. Although extensive research has been conducted, a comprehensive understanding of these conditions remains elusive. Current clinical diagnosis often relies on the application of integrated diagnostic criteria for IgG4-related diseases, combined with specific organ involvement criteria. Distinguishing them from malignancies poses considerable challenges. Moreover, further investigations are required to elucidate the underlying pathogenic mechanisms and explore potential therapeutic interventions. This review provides a systematic classification of IgG4-related digestive diseases while discussing their diagnostic strategies, clinical presentations, and treatment modalities. The comprehensive insights shared herein aim to guide clinicians in their practice and contribute to the advancement of knowledge in this field.

Characteristics of mass-forming autoimmune pancreatitis commonly misdiagnosed as a malignant tumor

Objective

This study aimed to explore the clinical characteristics and differential diagnosis of patients with autoimmune pancreatitis (AIP) and pancreatic cancer to prevent misdiagnosis and mistreatment.

Methods

The clinical data of patients with AIP with suspected pancreatic or bile duct malignancy and pancreatic cancer were retrospectively analyzed. The risk factors and the diagnostic value of IgG4 and Tbil levels before treatment for AIP was investigated. Moreover, the imaging features and response to hormone therapy were analyzed.

Results

AIP was commonly observed in men. Compared to patients with pancreatic cancer, the incidence of poor appetite and weight loss and carbohydrate antigen 19-9 (CA19-9) level was lower in patients with AIP, while the immunoglobulin G4 (IgG4) level was higher (p < 0.05). After treatment, the IgG4 and CA19-9 levels in patients with AIP were decreased (p < 0.001). IgG4 level before treatment (OR = 2.452, 95%CI: 1.180-5.096, P = 0.016) and total bilirubin (Tbil) level before treatment (OR = 0.992, 95%CI: 0.985-0.998, P = 0.013) were independent risk factors of AIP. Furthermore, the diagnostic value of IgG4 level before treatment, Tbil level before treatment, IgG4/Tbil before treatment, and a combination of these indicators was high. Moreover, 15 (68.18%) patients with AIP had space-occupying lesions of the pancreas, and 16 (72.73%) had autoimmune cholangitis. Most patients with AIP were sensitive to hormone therapy.

Conclusions

The Tbil and IgG4 levels, imaging findings, and hormone therapy reactivity could differentiate AIP from pancreatic cancer. A combination of IgG4, Tbil, and IgG4/Tbil before treatment might be a promising diagnostic biomarker for AIP.

A multidomain fusion model of radiomics and deep learning to discriminate between PDAC and AIP based on 18F-FDG PET/CT images

PURPOSE

To explore a multidomain fusion model of radiomics and deep learning features based on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) images to distinguish pancreatic ductal adenocarcinoma (PDAC) and autoimmune pancreatitis (AIP), which could effectively improve the accuracy of diseases diagnosis.

MATERIALS AND METHODS

This retrospective study included 48 patients with AIP (mean age, 65 ± 12.0 years; range, 37-90 years) and 64 patients with PDAC patients (mean age, 66 ± 11.3 years; range, 32-88 years). Three different methods were discussed to identify PDAC and AIP based on ¹⁸F-FDG PET/CT images, including the radiomics model (RAD_model), the deep learning model (DL_model), and the multidomain fusion model (MF_model). We also compared the classification results of PET/CT, PET, and CT images in these three models. In addition, we explored the attributes of deep learning abstract features by analyzing the correlation between radiomics and deep learning features. Five-fold cross-validation was used to calculate receiver operating characteristic (ROC), area under the roc curve (AUC), accuracy (Acc), sensitivity (Sen), and specificity (Spe) to quantitatively evaluate the performance of different classification models.

RESULTS

The experimental results showed that the multidomain fusion model had the best comprehensive performance compared with radiomics and deep learning models, and the AUC, accuracy, sensitivity, specificity were 96.4% (95% CI 95.4-97.3%), 90.1% (95% CI 88.7-91.5%), 87.5% (95% CI 84.3-90.6%), and 93.0% (95% CI 90.3-95.6%), respectively. And our study proved that the multimodal features of PET/CT were superior to using either PET or CT features alone. First-order features of radiomics provided valuable complementary information for the deep learning model.

CONCLUSION

The preliminary results of this paper demonstrated that our proposed multidomain fusion model fully exploits the value of radiomics and deep learning features based on ¹⁸F-FDG PET/CT images, which provided competitive accuracy for the discrimination of PDAC and AIP.

Steriod for Autoimmune pancreatitis complicating by gastric varices: A case report

BACKGROUND

Both autoimmune pancreatitis (AIP) and gastric varices are related to various diseases. However, AIP complicated by gastric varices is extremely rare, and has only been reported in a few studies. Here, we report a case of AIP complicated by gastric varices in a female Chinese patient.

CASE SUMMARY

A 59-year-old Chinese woman was admitted to our hospital with mild abdominal pain. Computed tomography and magnetic resonance cholangiopancreatography revealed a diffusely enlarged pancreas, an obstructed splenic vein and slight splenomegaly. Esophagogastroduodenoscopy showed gastric varices in the partial gastric fundus and the red-color sign was positive. Blood chemistry showed that IgG4 was notablely elevated. The patient was diagnosed with AIP complicated by gastric varices. Steroid therapy was administered to this patient with the risk of gastrointestinal bleeding. After one year of therapy, the pancreas, spleen and splenic vein recovered to the normal states, and the gastric varices had disappeared.

CONCLUSION

We present this case together with evidence from the literature to demonstrate the effectiveness of steroid therapy in the treatment of AIP complicated by gastric varices.

The Clinical Phenotype of Chinese Patients With Autoimmune Pancreatitis Differs Significantly From Western Patients

Aim

To characterize the clinical features of autoimmune pancreatitis (AIP) in China and compare differences between our Chinese cohort and Western cohorts.

Methods

This was a retrospective study of patients with AIP that was carried out in the China-Japan Friendship Hospital between January 2010 and April 2021. We included a total of 50 patients (46 males and 4 females) aged between 27 and 86 years who fulfilled the international Consensus Diagnostic (ICD) Criteria. For comparative purposes, we included data from seven representative Western cohorts.

Result

When comparing Chinese and Western patients, we found that obstructive jaundice was the most frequent initial symptom (68 vs. 43%, P < 0.001). Extra-pancreatic organ involvement was more common in Chinese patients (68 vs. 30%, P < 0.001). Sclerosing cholangitis was the most frequent extrapancreatic lesion (48 vs. 24%, P = 0.001). The elevation of serum IgG4 was more obvious in our cohort (86 vs. 49%, P < 0.001). Conversely, the rates of ANA-positivity were significantly higher in Western populations (17 vs. 50%, P = 0.006). With regards to imaging, diffuse swelling was significantly more common in China (44 vs. 27%, P = 0.021). Steroid therapy was used more frequently in our Chinese patients (84 vs. 59%, P = 0.001). The steroid-response rate was also significantly higher in our Chinese patients (85 vs. 54%, P = 0.001); However, the rate of resection was higher in Western cohorts (2 vs. 31%, P < 0.001). There was no significant difference between the two populations with regards to recurrence rate (33 vs. 33%, P = 1.000).

Conclusion

This study identified significant differences between Chinese and Western populations of patients with AIP. Within the Chinese population, AIP was more likely to have jaundice and extra-pancreatic organ involvement, and elevated serum IgG4 levels. Chinese patients were also showed favorable responses to treatment with glucocorticoids.

Autoimmune pancreatitis: What we know so far

Autoimmune pancreatitis (AIP) is a rare, often‐missed disease that involves inflammation of the pancreas and strictures of the pancreatic duct. Its prevalence and incidence in the United States remain scarce. The disease has a varied presentation and often mimics pancreatic malignancy, which can make the diagnosis challenging. Most patients have an excellent response to corticosteroid therapy. Immunomodulators may be used in some cases. Rituximab is an effective, emerging treatment in steroid‐refractory cases. This study aims to review the two distinct types of AIP and provide a detailed analysis of the diagnostic approach and treatment modalities.

Technical and Clinical Aspects of Diagnostic Single-Balloon Enteroscopy in the First Decade of Use: A Systematic Review and Meta-Analysis

Background/Aims

Single-balloon enteroscopy (SBE) has been widely used in diagnosing small bowel disease. We conducted this study to systematically appraise its technical and clinical performance.

Methods

Studies on SBE published by September 2018 were systematically searched. Technical and clinical performance data were collected and analyzed with descriptive or meta-analysis methods.

Results

In total, 54 articles incorporating 4,592 patients (6,036 procedures) were included. Regarding technical parameters, the pooled insertion depths (IDs) for anterograde and retrograde SBE were 209.2 cm and 98.1 cm, respectively. The pooled retrograde ID in Asian countries was significantly greater than that in Western countries (129.0 cm vs 81.1 cm, p<0.001). The pooled anterograde and retrograde procedure times were 57.6 minutes and 65.1 minutes, respectively. The total enteroscopy rate was 21.9%, with no significant difference between Asian and Western countries. Clinically, the pooled diagnostic yield of SBE was 62.3%. Obscure gastrointestinal bleeding (OGIB) was the most common indication (50.0%), with a diagnostic yield of 59.5%. Vascular lesions were the most common findings in Western OGIB patients (76.9%) but not in Asian ones (31.0%). The rates of severe and mild adverse events were 0.5% and 2.5%, respectively.

Conclusions

SBE is technically efficient and is clinically effective and safe, but total enteroscopy is relatively difficult to achieve with this technique. Etiologies of OGIB in Asian countries differ from those in Western countries.

Radiomics model of dual-time 2-[18F]FDG PET/CT imaging to distinguish between pancreatic ductal adenocarcinoma and autoimmune pancreatitis

OBJECTIVES

Pancreatic ductal adenocarcinoma (PDAC) and autoimmune pancreatitis (AIP) are diseases with a highly analogous visual presentation that are difficult to distinguish by imaging. The purpose of this research was to create a radiomics-based prediction model using dual-time PET/CT imaging for the noninvasive classification of PDAC and AIP lesions.

METHODS

This retrospective study was performed on 112 patients (48 patients with AIP and 64 patients with PDAC). All cases were confirmed by imaging and clinical follow-up, and/or pathology. A total of 502 radiomics features were extracted from the dual-time PET/CT images to develop a radiomics decision model. An additional 12 maximum intensity projection (MIP) features were also calculated to further improve the radiomics model. The optimal radiomics feature set was selected by support vector machine recursive feature elimination (SVM-RFE), and the final classifier was built using a linear SVM. The performance of the proposed dual-time model was evaluated using nested cross-validation for accuracy, sensitivity, specificity, and area under the curve (AUC).

RESULTS

The final prediction model was developed from a combination of the SVM-RFE and linear SVM with the required quantitative features. The multimodal and multidimensional features performed well for classification (average AUC: 0.9668, accuracy: 89.91%, sensitivity: 85.31%, specificity: 96.04%).

CONCLUSIONS

The radiomics model based on 2-[¹⁸F]fluoro-2-deoxy-D-glucose (2-[¹⁸F]FDG) PET/CT dual-time images provided promising performance for discriminating between patients with benign AIP and malignant PDAC lesions, which shows its potential for use as a diagnostic tool for clinical decision-making.

KEY POINTS

• The clinical symptoms and imaging visual presentations of PDAC and AIP are highly similar, and accurate differentiation of PDAC and AIP lesions is difficult. • Radiomics features provided a potential noninvasive method for differentiation of AIP from PDAC. • The diagnostic performance of the proposed radiomics model indicates its potential to assist doctors in making treatment decisions.

Primary lymphomas of the intraabdominal solid organs and the gastrointestinal tract: spectrum of imaging findings with histopathological confirmation

Unlike nodal lymphoma, primary lymphomas of the intraabdominal organs are uncommon neoplasms whose diagnosis may be challenging in certain clinical circumstances. Despite this difficulty for imaging diagnosis, there are several imaging features on ultrasonography, computed tomography, magnetic resonance imaging, and positron emission tomography that may suggest the correct diagnosis. The scope of this review is to describe and illustrate the imaging features of primary lymphoma of intraabdominal organs providing clues to the diagnosis, together with their pathological correlations.

The role of EUS-guided fine needle aspiration in autoimmune pancreatitis: a single center prospective study

OBJECTIVES

Histopathological examination is pivotal in diagnosing autoimmune pancreatitis (AIP). The usefulness of EUS-guided fine needle aspiration (EUS-FNA) in diagnosing AIP remains controversial worldwide. The authors conducted this study to evaluate the efficacy of EUS-FNA for AIP diagnosis using a 22-gauge needle.

METHODS

Between January 2013 and May 2017, 37 patients had imaging studies suggestive of AIP at Tongji Hospital, and 27 patients of them were enrolled in this study. Tissue specimens acquired through EUS-FNA were analyzed for periductal lymphoplasmacytic infiltrate (LPI), storiform fibrosis (SF), obliterative phlebitis (OP) and immunoglobulin G4 (IgG4)-positive plasma cell counts. Clinical Trials.gov no: TJ-C20121220.

RESULTS

LPI and SF were present in 18 (66.67%) and 18 (66.67%) of 27 patients, respectively. Abundant IgG4-positive plasmacyte infiltration >10/high-power field (HPF) was detected in 8 of 27 patients (29.63%). OP and the characteristic findings of idiopathic duct-centric chronic pancreatitis (IDCP) and granulocytic epithelial lesion (GEL) were not detected in this study. According to the International Consensus Diagnostic Criteria (ICDC) for AIP, 5 and 12 of 27 patients were assessed as having level 1 and level 2 histological findings, respectively, suggesting that 17 of 27 patients (62.96%) had lymphoplasmacytic sclerosing pancreatitis (LPSP) based on the ICDC.

CONCLUSIONS

In 92.6% of patients, pancreatic tissues with >5 HPFs were obtained by EUS-FNA using a 22-G needle. In 63% of patients, histology was evaluated to be ≥ level 2 according to the ICDC. The study indicates that EUS-FNA with a 22-G needle is valuable in the histopathological diagnosis of AIP.

Prediction and Management for Relapse of Type 1 Autoimmune Pancreatitis After Initial Steroid Treatment: A Long-Term Follow-up From China

OBJECTIVES

This study aimed to investigate the frequency, predictors, and management of relapse of type 1 autoimmune pancreatitis (AIP) after steroid treatment.

METHODS

One hundred one patients with type 1 AIP receiving steroid as initial treatment were enrolled. Predictors were identified by multivariate analysis using Cox proportional hazards model. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

Thirty-nine (41.1%) patients experienced relapse after steroid treatment during a median follow-up of 40 months. The cumulative rate of relapse reached a plateau at 57.6% (95% CI, 50.3%-64.9%) at 59 months. Without maintenance therapy (HR, 4.53; 95% CI, 1.35-15.17) and proximal bile duct involvement (HR, 2.10; 95% CI, 1.07-4.14) were identified as risk factors. Repeated steroid treatment with the same initial dose but longer induction and tapering duration was given to 87.2% patients with relapse and obtained response (97.1%) during a short-term follow-up (median, 19 months).

CONCLUSIONS

Relapses are common in type 1 AIP after steroid treatment. Without maintenance therapy and proximal bile duct involvement were risk factors. Repeated steroid treatment with longer duration is effective for relapse.

Outcome and Genetic Factors in IgG4-Associated Autoimmune Pancreatitis and Cholangitis: A Single Center Experience

Introduction. Most investigations on autoimmune pancreatitis (AIP) were published on Asian cohorts while those on Caucasians are limited. However, there might be differences related to the origin. Patients and Methods. We analyzed 36 patients and compared type 1 (AIP1) with type 2 (AIP2). Results. The majority of patients suffered from AIP1 (55.6%). AIP1 patients were significantly older than AIP2 patients (54.4 versus 40.8 years). Moreover, 85.0% of AIP1 patients had concurrent autoimmune cholangitis (AIC) while 18.8% of AIP2 patients suffered from overlap to ulcerative colitis (UC). However, AIP1 patients revealed a cholestatic course and had significantly higher immunoglobulin G4 levels (IgG4). When compared to allele frequencies in healthy controls, in patients with AIP1 HLA-B8 reached statistical significance. Response to steroids was excellent in both groups, but we noticed high rates of relapse especially in AIP1 patients. Finally, 3 patients with AIP1 were diagnosed with cholangiocellular carcinoma (CCC). Conclusion. In contrast to Asian studies, we found an almost equal distribution of AIP1 and AIP2 patients in our German cohort. AIP2 patients were younger and mostly of female gender whereas AIP1 patients revealed higher IgG4 levels and involvement of the biliary tract in sense of IgG4-associated cholangitis.

From Pathogenesis, Clinical Manifestation, and Diagnosis to Treatment: An Overview on Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP) is a special type of chronic pancreatitis which is autoimmune mediated. The international consensus diagnostic criteria (ICDC) 2011 proposed two types of AIP: type I is associated with histological pattern of lymphoplasmacytic sclerosing pancreatitis (LPSP), characterized by serum IgG4 elevation, whereas type 2 is named idiopathic duct-centric pancreatitis (IDCP), with granulocytic epithelial lesion (GEL) and immunoglobulin G4 (IgG4) negative. The pathogenic mechanism is unclear now; based on genetic factors, disease specific or related antigens, innate and adaptive immunity may be involved. The most common clinical manifestations of AIP are obstructive jaundice and upper abdominal pain. The diagnosis can be made by a combination of parenchymal and ductal imaging, serum IgG4 concentrations, pancreatic histology, extrapancreatic disease, and glucocorticoid responsiveness according to ICDC 2011. Because of the clinical and imaging similarities with pancreatic cancer, general work-up should be done carefully to exclude pancreatic malignant tumor before empirical trial of glucocorticoid treatment. Glucocorticoid is the most common drug for AIP to induce remission, while there still exists controversy on steroid maintenance and treatment for relapse. Further studies should be done to identify more specific serum biomarkers for AIP, the pathogenic mechanisms, and the treatment for relapse.

Autoimmune pancreatitis

Autoimmune pancreatitis (AIP) is a rare, distinct and increasingly recognized form of pancreatitis which has autoimmune features. The international consensus diagnostic criteria (ICDC) for AIP recently described two subtypes; type 1[lymphoplasmacytic sclerosing pancreatitis (LPSP)] and type 2 [idiopathic duct-centric pancreatitis (IDCP) or AIP with granulocytic epithelial lesion (GEL)]. Type 1 is the more common form of the disease worldwide and current understanding suggests that it is a pancreatic manifestation of immunoglobulin G4-related disease (IgG4-RD). In contrast, type 2 AIP is a pancreas-specific disease not associated with IgG4 and mostly without the overt extra-pancreatic organ involvement seen in type 1. The pathogenesis of AIP is not completely understood and its clinical presentation is non-specific. It shares overlapping features with more sinister pathologies such as cancer of the pancreas, which continues to pose a diagnostic challenge for clinicians. The diagnostic criteria requires a variable combination of histopathological, imaging and serological features in the presence of typical extrapancreatic lesions and a predictable response to steroids.

Hybrid kappa\lambda antibody is a new serological marker to diagnose autoimmune pancreatitis and differentiate it from pancreatic cancer

The only generally accepted serological marker currently used for the diagnosis of autoimmune pancreatitis (AIP) is IgG4. Our aim was mainly to determine whether hybrid κ\λ antibody can help to diagnose AIP and to differentiate it from pancreatic cancer. We established an enzyme-linked immunosorbent assay (ELISA) system to measure the levels of hybrid κ\λ antibodies in human sera. Sera were obtained from 338 patients, including 61 with AIP, 74 with pancreatic cancer, 50 with acute pancreatitis, 40 with ordinary chronic pancreatitis, 15 with miscellaneous pancreatic diseases, and 98 with normal pancreas. Our study showed levels of hybrid κ\λ antibodies in the AIP group were significantly higher than in the non-AIP group (P < 0.001). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the diagnosis of AIP were 80.3%, 91%, 66.2% and 95.5% respectively. Furthermore, the combined measurement of serum hybrid κ\λ antibody and IgG4 tended to increase the sensitivity although the difference was not statistically significant (90.2% vs. 78.7%, P = 0.08), compared to measurement of IgG4 alone. Our findings suggest that hybrid κ\λ antibody could be a new serological marker to diagnose AIP and differentiate it from pancreatic cancer.