By Kristina Fiore, Staff Writer, MedPage Today
Published: January 19, 2011
Reviewed by Zalman S. Agus, MD; Emeritus Professor
University of Pennsylvania School of Medicine and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner
Nucleic acid testing for hepatitis B virus (HBV) in blood donors may catch potential infection during transfusion, researchers said.
The screen picked up nine cases of the virus in a sample of 3.7 million donors -- more than triple the expected infection rate in this population, Susan Stramer, PhD, of the American Red Cross in Rockville, Md., and colleagues reported in the Jan. 20 issue of the New England Journal of Medicine.
"This study showed a higher-than-expected rate of HBV infection with the use of triplex nucleic acid testing, mainly in donors who had been vaccinated against HBV and who would not have been identified by routine screening," they wrote.
Yet they noted that the acute infections resolved quickly, and their clinical significance in terms of transmission potential isn't clear.
Hepatitis B screening in donors currently tests for disease-specific surface antigen (HBsAg) or for antibodies against hepatitis B core antigen (anti-HBc).
Yet not all donors who have hepatitis B DNA are identified during the period before seroconversion.
So the researchers hypothesized that combination nucleic acid testing for hepatitis B and C as well as HIB in a single triplex assay may provide additional safety.
They performed nucleic acid testing on 3.7 million blood donations and further evaluated the hepatitis B DNA-positive samples that were negative for HBsAg and anti-HBc.
They found nine donors who had hepatitis B DNA, which translated to an overall rate of one in 410,540 donations -- far larger than the two to four expected based on modeling studies, the researchers said.
Six of the samples came from donors who'd received the hepatitis B vaccine and had subclinical infections that developed and resolved.
The investigators said the blood of donors with acute infection during the window period is likely to be highly infectious in transfusion recipients, although the significance of infection in vaccinated donors is less clear.
"These acute HBV infections rapidly resolved and are of inconsequential significance, but their potential for transmission remains unresolved," they wrote.
Three patients who weren't vaccinated and tested positive in nucleic acid screening for hepatitis B had acute infection with subgenotype A2, which is the most frequent genotype in the U.S. and is the parent strain of the HBV vaccine.
On the other hand, only one of the six vaccinated donors were infected with the A2 subtype. The others had non-A2 strains.
The researchers said the findings "emphasize the protective effect of the vaccine, since the observed infections were transient, blunted, and without effect on liver function," but noted that it is less effective for non-A2 infections.
Overall, only two cases of liver injury occurred among those nine hepatitis B DNA-positive patients, and they were in unvaccinated donors.
The researchers attributed infection in four of the DNA-positive donors to a chronically infected sexual partner.
They noted that the infrequent detection of transfusion-transmitted infection contributes to the low cost-effectiveness of nucleic acid testing. Yet in their sample, they found that of 75 reactive nucleic acid tests in seronegative blood samples, 25 were confirmed as positive for either hepatitis B, hepatitis C, or HIV.
Thus, they called for the development of new tests in order to get around the high cost of introducing new screening assays for blood donors and concluded that their findings "may be relevant to decisions about the need to implement screening for HBV DNA among blood donors."
The researchers reported relationships with MacoPharma, Novartis, Abbott Diagnostics, Novartis Vaccines and Diagnostics, Abbott, Roche, Siemens, and Gen-Probe.
Primary source: New England Journal of Medicine
Source reference:
Stramer SL, et al "Nucleic acid testing to detect HBV infection in blood donors" N Engl J Med 2011; 364: 236-247.
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