In my opinion it would have been better to evalu- ate the HBV DNA in all the hemodialysis patients, not just in the 18 anti-HBV core antibody-positive cases, as more cases with OHB may have been found in this high-risk group. Moreover, information regarding the history of HBV vaccination, icterus and diabetes mellitus status were missing from the article, which would have been improved had this informa- tion been present. Finally, I would like to mention that detection of virus-specific nucleic acid does not always indicate infection (8). Seyed Moayed Alavian Professor of Gastroenterology and Hepatology, Director of the Baqiyatallah Research Center for Gastroenterology and Liver Diseases, Tehran, Iran Email: alavian@thc.ir REFERENCES 1. Aghakhani A, Banifazl M, Kalantar E et al. Occult hepatitis B virus infection in hemodialysis patients with isolated hepatitis B core antibody: A multicenter study. Ther Apher Dial 2010;14: 349–53. 2. Mahdavimazdeh M, Hosseini-Moghaddam SM, Alavian SM, Yahyazadeh H. Hepatitis B infection in hemodialysis patients in Tehran Province, Iran. Hepat Mon 2009;9:206– 10. 3. Hollinger FB, Habibollahi P, Daneshmand A, Alavian SM. Occult hepatitis B infection in chronic hemodialysis patients: current cocepts and strategy. Hepat Mon 2010;10:199– 204. 4. Alavian SM, Bagheri-Lankarani K, Mahdavi-Mazdeh M, Nourozi S. Hepatitis B and C in dialysis units in Iran: Changing the epidemiology. Hemodial Int 2008;12:378–82. 5. Habibollahi P, Safari S, Daryani NE, Alavian SM. Occult hepa- titis B infection and its possible impact on chronic hepatitis C virus infection. Saudi J Gastroenterol 2009;15:220–4. 6. Alavian SM. A shield against a monster: hepatitis C in hemodialysis patients. World J Gastroenterol 2009;15:641– 6. 7. Alavian SM, Tabatabaei SV. The effect of diabetes mellitus on immunological response to hepatitis B virus vaccine in individu- als with chronic kidney disease: A meta-analysis of current lit- erature. Vaccine 2010;28:3773–7. 8. Hollinger FB, Sood G. Occult hepatitis B virus infection: A covert operation. J Viral Hepat 2010;17:1–15. Occult Hepatitis B Virus Infection in Hemodialysis Patients With Isolated Hepatitis B Core Antibody: A Multicenter Study Dear Editor, We appreciate the interest and comments on our manuscript regarding “Occult Hepatitis B Virus Infection in Hemodialysis Patients with Isolated Hepatitis B Core Antibody: A Multicenter Study” (1); our comments can be found below. As we men- tioned in our paper, some studies showed an associa- tion between hepatitis C virus (HCV) and occult hepatitis B virus (HBV) infection (2–4), but because only one of our patients with occult HBV was co-infected with HCV, a conclusion cannot be reached regarding the association of occult HBV infection and HCV in this survey (1). The letter from Professor Alavian (8) mentioned that our occult HBV positive cases were focused in one dialysis center, but we clearly explained in our paper that we studied 289 patients on chronic hemo- dialysis (HD) from five dialysis units in Tehran, Iran, not just from one dialysis center; patients with isolated hepatitis B core antibody (anti-HBc) were found in only two dialysis units. One dialysis unit showed five cases of occult HBV infection from six patients with isolated anti-HBc and the other one had four patients with occult HBV infection from 12 isolated anti-HBc patients (1). Sequencing of HBV-DNA-positive samples was a good suggestion and it was done in another study and recently published (5). Besides, it is clear that HBV vaccination can control HBV acquisi- tion in HD patients, although the antibody response is suboptimal and an antibody titer above 100 IU/L fol- lowing primary vaccination is necessary in order to maintain the protective levels of antibody (6,7). It is definitely better to evaluate HBV-DNA in all HD patients, but the aim of this study was to assess the occult HBV infection in hemodialysis patients with isolated anti-HBc; a history of HBV vaccination, icterus and diabetes mellitus were not related to this study. Arezoo Aghakhani, 1 Mohammad Banifazl, 2 and Amitis Ramezani 1 1 Clinical Research Department, Pasteur Institute of Iran, and 2 Iranian Society for Support Patients with Infectious Diseases, Tehran, Iran E-mail: iiccom@iiccom.org Letters to the Editor 610 © 2010 The Authors Journal compilation © 2010 International Society for Apheresis Ther Apher Dial, Vol. 14, No. 6, 2010