The American Journal of GASTROENTEROLOGY VOLUME 104 | JULY 2009 www.amjgastro.com 1854 Letters to the Editor patient, sorafenib has allowed achieve- ment of a satisfactory tumor control that granted an improved quality of life at long-term follow-up. In summary, this report describes our experience with a case of HCC and PVTT that showed a beneficial clinical response during sorafenib treatment, which was associated with an evident reduction of HCC mass and revasculari- zation of PVTT. CONFLICT OF INTEREST e authors declare no conflict of interest. REFERENCES 1. Manzanet G, Sanjuán F , Orbis P et al. Liver transplantation in patients with portal vein thrombosis. Liver Transpl 2001;7: 125–31. 2. Amitrano L, Guardascione M, Brancaccio V et al. Risk factors and clinical presentation of portal vein thrombosis in patients with liver cirrhosis. J Hepatol 2004;40:736–41. 3. Pirisi M, Avellini C, Fabris C et al. Portal vein thrombosis in hepatocellular carcinoma: Age and sex distribution in an autopsy study . J Cancer Res Clin Oncol 1998;124:397–400. 4. Stuart KE, Anand AJ , Jenkins RL. Hepatocel- lular carcinoma in the United States. Prognostic features, treatment outcome, and survival. Cancer 1996;77:2217–22. 5. Ando E, Yamashita F , Tanaka M et al. A novel chemotherapy for advanced hepatocellular carcinoma with tumor thrombosis of the main trunk of the portal vein. Cancer 1997;79:1890–6. 6. Llovet JM, Bustamante J , Castells A et al. Natu- ral history of untreated nonsurgical hepatocel- lular carcinoma: Rationale for the design and evaluation of therapeutic trials. Hepatology 1999;29:62–7. 7. Llovet JM, Ricci S, Mazzaferro V et al. Sorafenib in advanced hepatocellular carcinoma. N Engl J Med 2008;359:378–90. 8. Eisenhauer EA, erasse P , Bogaerts J et al. New response evaluation criteria in solid tu- mours: revised RECIST guideline. Eur J Cancer 2009;45:228–47. 9. Llovet JM, Di Bisceglie AM, Bruix J et al. Design and endpoints of clinical trials in hepatocellular carcinoma. J Nat Cancer Inst 2008;100:698–711. 10. Li Q , Xu B, Fu L et al. Correlation of four vascu- lar specific growth factors with carcinogenesis and portal vein tumor thrombus formation in human hepatocellular carcinoma. J Exp Clin Cancer Res 2006;25:403–9. 1 Department of Internal Medicine, Gemelli Hospital, Catholic University of Rome, Rome, Italy; 2 Department of Radiology, Gemelli Hospital, Catholic University of Rome, Rome, Italy. Correspondence: Antonio Gasbarrini, MD, Department of Internal Medicine, Gemelli Hospital, Catholic University of Rome, Largo A. Gemelli, Rome 8 - 00168, Italy. E-mail: agasbarrini@rm.unicatt.it Distinguishing Between Anti-Neutrophil Cytoplasmic Antibody Patterns in Inflammatory Bowel Disease: Is the “Atypical Pattern” Adding More Information? Josué Barahona-Garrido, MD 1–4 , Jorge Hernández-Calleros, MD 2 , Javier Cabiedes, PhD 5 , Helga M. Sarti, MD 6 , Aldo Torre, MD 2,3 , Aldo J. Montaño-Loza, MD, 2,3 and Jesús K. Yamamoto-Furusho, MD, PhD 1–3 doi:10.1038/ajg.2009.144; published online 12 May 2009 To the Editor: We read with interest the article by Desplat-Jégo et al . regard- ing update on Anti– Saccharomyces cerevisiae antibodies (1). Perinuclear anti-neutrophil cytoplasmic antibody (p-ANCA) is associated with inflamma- tory bowel disease (IBD), more com- monly in patients with ulcerative colitis (UC) than in patients with Crohn ’ s dis- ease (CD). For the p-ANCA test, anti- bodies are incubated on ethanol-fixed neutrophils and are then analyzed by indirect immunofluorescence micros- copy. Using formalin-fixed neutrophils enables the distinction of a different sub- set of antibodies called atypical ANCA (x-ANCA), which is generating interest because they recognize recently discov- ered bacterial antigens that may trigger IBD. We would like to emphasize the importance of distinguishing between p-ANCA and x-ANCA. Some stud- ies have shown that x-ANCA is present in IBD-associated autoimmune liver and biliary diseases, such as primary sclerosing cholangitis and autoimmune hepatitis, in which evidence of the poten- tial role of bacterial antigens has recently emerged. e x-ANCAs recognize pro- teins in human neutrophils (tubulin-β isoform 5) and bacteria (bacterial cell division protein FtsZ), suggesting cross- recognition between microbial antigens in the gut and components of the immune system, which is probably implicated in the pathogenesis of IBD (2). Desplat-Jégo et al. found that the prevalence of x-ANCAs in the French population is 71.8% in UC patients, 11% in CD, and 0% in healthy blood donors (1). Before recognition of the differences between x-ANCA and p-ANCA patterns, the prevalence of p-ANCAs in Mexican patients with UC was reported to be 51% (3); aſterward, the prevalence of each pat- tern was reported in 48 and 28%, respec- tively (4). Between September 2006 and August 2008, with the aim of determin- ing their diagnostic yield, we investigated these patterns in a cohort of 184 Mexican patients with IBD (UC = 160, CD = 24). In UC patients, we found higher prevalence of x-ANCAs than p-ANCAs (50 vs. 32%), along with higher specificity (96 vs. 92%) and positive predictive value (99 vs. 96%). In CD patients, prevalence, specificity, and positive predictive value were lower ( Table 1). e importance of x-ANCA and p-ANCA rests on their high posi- tive predictive value for UC, and mod- erate-to-high negative predictive value for CD (78 and 83%, respectively). ere are few reports in which the x-ANCA is described, but to our best knowledge, this is the first study that compares the diag- nostic yield of x-ANCA and p-ANCA in a single cohort of patients with UC and CD; therefore, we need more studies regarding its potential clinical application. It is important to mention that for confirming the x-ANCA pattern, it is necessary to incubate antibodies in for- malin-fixed neutrophils instead of the traditional ethanol-fixed neutrophils used to search for p-ANCAs. Forma- lin prevents neutrophil antigens in the cytoplasm from migrating to the nuclear membrane and hence showing its charac- teristic features by indirect immunofluo- rescence ( Figure 1). Finally, the utility of the test for x-ANCA in combination with newer markers derived from microbial spe- cies of the gut remains to be addressed. Despite the fact that the combination of antibodies increases the accuracy of diagnosis, the perfect assays are far yet to