Prevalence of occult HBV in hemodialysis patients is 4 to 5 times higher than standard HBsAg testing would suggest

Some kidney dialysis patients contract hepatitis B virus (HBV) during the course of their treatment, possibly from other members of the dialysis population with occult HBV. People with occult HBV test negative for HBV surface antigen (HBsAg) but positive for HBV-DNA, which is detected through sensitive tests not typically performed on dialysis patients.

A recent study found that the prevalence of occult HBV in adult hemodialysis patients is four to five times higher than standard HBsAg testing would suggest. These findings are published in the November 2004 issue of Hepatology.

Hepatology, the official journal of the American Association for the Study of Liver Diseases (AASLD), published by John Wiley & Sons, Inc., is available online via Wiley InterScience.

Previous studies that have looked for evidence of occult HBV in dialysis patients have found a wide range of infection rates – from 0 to 50 percent -- possibly due to the differences in the study populations. In this study, researchers, led by Dr. Gerald Y. Minuk of the University of Manitoba, sought to find the prevalence of occult HBV in a large North American population of adult dialysis patients and to determine if any demographic, biochemical and/or serologic feature could help identify those infected.

Between May and September of 2003, the researchers recruited hemodialysis patients in Winnipeg, Manitoba, an urban area in Canada with a population of about 680,000. They drew blood from and recorded demographic data for each of the 241 participants. They then performed liver biochemistry, HBV serology, and HBV-DNA testing by real-time polymerase chain reaction with two independent primer sets.

Only two of the participants tested positive for HBsAg, but an additional nine patients were found to have occult HBV, that is, they tested negative for HBsAg and positive for HBV-DNA.

"The results of this study indicate that in this North American urban centre, the prevalence of occult HBV in adult hemodialysis patients is approximately 4 to 5 times higher than standard HBsAg testing would suggest," the authors report. The majority of the infections were associated with low viral loads and a surprisingly high prevalence of the sG145R-mutant.

Unfortunately, but not unexpectedly, there were no obvious demographic, biochemical or serologic indicators for those with occult HBV. For the nine patients with occult HBV, the mean age was 61.4 years and 56 percent were male. Seventy-eight percent were Caucasian, and two were Southeast Asian. All had normal liver enzyme and function tests.

Occult HBV infection can be transmitted to others, according to available data involving chimpanzees, infants and transfusion and organ recipients. "Until data exist indicating whether nosocomial transmission of occult HBV can occur in susceptible dialysis patients and/or staff, screening with sensitive PCR-based assays of all dialysis patients for HBV-DNA regardless of demographic, biochemical or serologic findings seems prudent," the authors conclude.

If occult HBV status is known, transmission among dialysis patients might be limited by avoiding dialyzer reuse and dedicating dialysis rooms, machines and staff for infected patients. Vaccinations may also protect dialysis patients from contracting HBV, however, vaccination acceptance and response rates are low in this population of dialysis patients.