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Diagnosing autoimmune pancreatitis: choosing your weapon

      Abbreviations:

      AIP (autoimmune pancreatitis), FNB (fine-needle biopsy), ICDC (International Consensus Diagnostic Criteria), LPSP (lymphocytoplasmic sclerosing pancreatitis)
      Autoimmune pancreatitis (AIP) is a relatively newly discovered and rare disease that can be challenging to recognize and diagnose.
      • Zen Y.
      • Bogdanos D.P.
      • Kawa S.
      Type 1 autoimmune pancreatitis.
      Although a case report first described it in 1961, not until 1995 did it begin to be recognized as a clinical entity in a case series by Yoshida et al.
      • Yoshida K.
      • Toki F.
      • Takeuchi T.
      • et al.
      Chronic pancreatitis caused by an autoimmune abnormality.
      Type 1 AIP is the most common worldwide and is associated with IgG4-positive cells and histologic features described as lymphocytoplasmic sclerosing pancreatitis (LPSP) without granulocyte epithelial lesions, which are seen in type 2 AIP.
      • Shimosegawa T.
      • Chari S.T.
      • Frulloni L.
      • et al.
      International consensus diagnostic criteria for autoimmune pancreatitis: guidelines of the International Association of Pancreatology.
      AIP can mimic other diseases such as pancreatic cancer, primary sclerosing cholangitis, and cholangiocarcinoma, which makes a timely and correct diagnosis challenging, often with the need of supportive pathologic correlation. In this issue of Gastrointestinal Endoscopy, Kurita et al
      • Kurita A.
      • Yasukawa S.
      • Zen Y.
      • et al.
      Comparison of a 22-gauge Franseen-tip needle with a 20-gauge forward-bevel needle for the diagnosis of type 1 autoimmune pancreatitis: a prospective randomized, controlled multicenter study (COMPAS study).
      compare the sensitivity of EUS-guided fine-needle biopsy (FNB) with a 22-gauge Franseen needle (Acquire; Boston Scientific Corporation, Natick, Mass, USA) and a 20-gauge forward-bevel needle (ProCore; Cook Medical, Bloomington, Ind, USA) in helping diagnose type 1 AIP.
      Multiple different criteria exist currently that can aid in the diagnosis of AIP, such as the Mayo Clinic Histology, Imaging, Serology, Other organ involvement Response to therapy criteria, the International Consensus Diagnostic Criteria (ICDC), and the Korean diagnostic criteria. Although some cases of AIP can be diagnosed on the basis of these criteria without the need for tissue sampling, histologic findings are a part of the criteria in all of these scoring systems and can help seal the diagnosis in indeterminate cases.
      • Nagpal S.J.S.
      • Sharma A.
      • Chari S.T.
      Autoimmune pancreatitis.
      Previous studies have shown conflicting data for the use of EUS-FNA for the diagnosis of AIP; however, the sensitivity is poor at roughly 43% to 60%.
      • Iwashita T.
      • Yasuda I.
      • Doi S.
      • et al.
      Use of samples from endoscopic ultrasound–guided 19-gauge fine-needle aspiration in diagnosis of autoimmune pancreatitis.
      • Kanno A.
      • Ishida K.
      • Hamada S.
      • et al.
      Diagnosis of autoimmune pancreatitis by EUS-FNA by using a 22-gauge needle based on the International Consensus Diagnostic Criteria.
      • Morishima T.
      • Kawashima H.
      • Ohno E.
      • et al.
      Prospective multicenter study on the usefulness of EUS-guided FNA biopsy for the diagnosis of autoimmune pancreatitis.
      Only very small studies have been published that examine the use of FNB needles to enable a histologic diagnosis of AIP. Although the results have been promising, these studies are not sufficient to guide clinical decision making, given the very small numbers of patients and the lack of randomization.
      The study by Kurita et al
      • Kurita A.
      • Yasukawa S.
      • Zen Y.
      • et al.
      Comparison of a 22-gauge Franseen-tip needle with a 20-gauge forward-bevel needle for the diagnosis of type 1 autoimmune pancreatitis: a prospective randomized, controlled multicenter study (COMPAS study).
      is the first prospective randomized multicenter trial that compares the sensitivity of different types of needle heads used for FNB in diagnosing type 1 AIP. The study initially included 110 patients thought to have type 1 AIP; however, alternative diagnoses were made in 9 of them, the final number of 101 patients with diagnosed AIP is included. The patients were gathered from 29 different sites in Japan. This is easily the largest study of its type.
      In this study, endoscopists performed a single needle pass into the pancreas with either a 22-gauge Franseen needle or a 20-gauge forward-bevel needle through a randomization process. After the lesion was punctured, the stylet was removed with suction with a 10-mL syringe. The endoscopist concurrently moved the needle in a to-and-fro manner 10 times within the lesion before needle withdrawal. Samples were then expelled into formalin with the stylet and sent for histologic analysis. Rapid on-site evaluation was not used for the study at any of the centers. Additional needle passes could have been made at the discretion of the endoscopist; however, material from these additional passes were placed in separate bottles and were not included in the study. Two blinded pathologists then reviewed the slides in terms of adequacy of sample and of histologic findings of type 1 AIP as defined by the ICDC.
      • Shimosegawa T.
      • Chari S.T.
      • Frulloni L.
      • et al.
      International consensus diagnostic criteria for autoimmune pancreatitis: guidelines of the International Association of Pancreatology.
      In all, there were 50 patients in the Franseen needle group and 51 patients in the forward-bevel needle group with confirmed type 1 AIP. A positive result in this study was defined as LPSP level 1 or level 2 findings based on the ICDC. Both groups had a technical success rate of 100%. The authors here found, however, that the 22-gauge Franseen needle obtained positive findings of LPSP level 1 or 2 in 39 of 50 type 1 AIP patients (sensitivity 78%), whereas the 20-gauge forward-bevel needle obtained positive findings in 23 of 51 patients (sensitivity 45%). Adverse events were rare, mild, and equal in both groups. This led the authors to conclude that the 22-gauge Franseen needle should be used routinely for histologic diagnosis of type 1 AIP and is superior to the forward-bevel needle.
      When the information provided is broken down, it is likely that what the authors have concluded is actually the correct message. The 22-gauge Franseen needle can be used for sampling in type 1 AIP, and on the basis of this limited information, it does appear to be more sensitive than the 20-gauge forward-bevel needle for diagnosing AIP with larger samples and a greater number of high-power fields. The real question, however, is how should this change or affect clinical practice? The answer to that question is a bit more difficult to tease out, given that multiple other factors could have been confounders in this study.
      First, the study was performed at many different centers. Although this does help add to the overall patient numbers in the study, it also means that each endoscopist was likely doing only a few cases at the most. A total of 101 patients at 29 centers yields an average of 3.5 patients per center. Further, 2 different needle types were used and possibly multiple endoscopists at each site. That means the true number of cases per endoscopist may be even lower, which means most endosonographers likely did not even get to use both needles that are compared. Other information about the endoscopists would be beneficial to know, such as how long they had been in practice, what their experience was like with each needle type, and how confident they felt with the single pass they made in each patient.
      Another potential issue here is that although the study specifically compares 2 different needle head types, it also uses 2 different gauges. Can we be certain that the differences in outcomes are due to the needle head type, not the gauge? Although there have been some conflicting data, a recent meta-analysis by Facciorusso et al
      • Facciorusso A.
      • Wani S.
      • Triantafyllou K.
      • et al.
      Comparative accuracy of needle sizes and designs for EUS tissue sampling of solid pancreatic masses: a network meta-analysis.
      examining different needle gauges in FNB of solid pancreatic lesions showed no difference in diagnostic yield among 19-, 22-, and 25-gauge needles. Solid pancreatic lesions, however, are a different disease process than type 1 AIP, so it is uncertain how applicable these data are to EUS-guided biopsy of the pancreas in AIP.
      In addition, a major question is this: Did the investigators compare the correct FNB needles that should be compared in detecting AIP? When solid pancreas masses are used as historical guides, the Franseen needle has been shown to be superior to the forward-bevel needle.
      • Karsenti F.
      • Thatsis G.
      • Burtin P.
      • et al.
      Comparison of 20-gauge Procore and 22-gauge Acquire needles for EUS-FNB of solid pancreatic masses: an observational study.
      Perhaps a better comparison would have been between the Franseen needle and the fork-tip FNB needle in the diagnosis of AIP, which has been shown to be equivalent in the diagnosis of solid pancreas masses.
      • Bang J.Y.
      • Herbert-Magee S.
      • Navaneethan U.
      • et al.
      Randomized trial comparing the Franseen and fork-tip needles for EUS-guided fine-needle biopsy sampling of solid pancreatic mass lesions.
      Endosonographers who have used the Franseen, fork-tip, and forward-bevel needles can readily attest to the increased success with the Franseen and fork-tip needles compared with the forward-bevel FNB needle; thus the more interesting and important comparison may likely be in examining the outcomes of the Franseen needle versus the fork-tip FNB needle in the diagnosis of AIP.
      An interesting point brought out by the study that should be important to endosonographers is that no matter what FNB needle is chosen in the attempt to make a histologic diagnosis of AIP, FNB-obtained specimens are not needed for a pathologic diagnosis in the majority of patients. Only 36 of the 110 patients in the study needed histologic analysis of EUS-guided FNB specimens to receive the diagnosis of AIP. Over two-thirds of the patients had the diagnosis of AIP made by ICDC clinical criteria alone without pathologic analysis. It is interesting to note that even though 63 patients had diseases that were “definitively diagnosed” as type 1 AIP without histologic findings, the investigators still performed EUS-guided FNB in these patients. Thus, what may be more important in diagnosing AIP is not what needle you choose, but that you may not need to perform any pancreas biopsy at all.
      In conclusion, this was a well-designed study comparing 2 separate EUS-guided needle types in performing FNB of the pancreas in patients with type 1 AIP. As stated previously, this is an important study given the lack of available data in regard to the diagnostic accuracy of different needles in this disease. Given the relative rarity of AIP, the authors were able to gather a moderately large number of cases throughout Japan, which lends strength to this study.
      What should be the takeaway here? In the selection of a needle type for biopsy in AIP patients, based on the information at hand, it can be said that a 22-gauge Franseen needle will yield a better diagnostic specimen than a 20-gauge forward-bevel needle. Given the multiple other variables listed above, it is difficult to say that all of the improvement in sampling with the Franseen needle is due to the type of needle head itself. More study is needed to compare the Franseen needle with other needle types, preferably in the same gauge, to rule out gauge as a variable. For now, if you are pulling out a needle to perform EUS-guided FNB of the pancreas to diagnose AIP, choose the Franseen needle, but remember that you may not need any needle at all.

      Disclosure

      All authors disclosed no financial relationships relevant to this publication.

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