CDC Testing Methods for Detecting HHV-6 Questionable

(Last week, we published a test conducted by the CDC that stated “there is no evidence that HHV-6A, 6B, 7 or any combination is associated with CFS.” The following takes another view of HHV-6 and CFS–editor)

Contrary to findings from the Center for Disease Control (the CDC), HHV-6 can indeed account for the clinical symptoms of CFS, according to research conducted by Konnie Knox, M.D., and Donald Carrigan, M.D., of ViraCor Diagnostic Labs.

The problem with the CDC testing, say Knox and Carrigan, is that it tested both patient and control groups using serum samples, lymphocytes and three polymerase chain reaction methods. According the two researchers, these tests are not an accurate means of detecting active HHV-6 infection.

Researchers at ViraCor state that “…in chronic HHV-6 infection, the amount of active HHV-6 (viral load) in the blood of a patient rises and falls periodically. When the viral load decreases, it may drop below the level of sensitivity of the culture assay. Therefore, if a patient tests negative, the first sample should be retested 60 to 90 days later.”

In studies conducted by ViraCor, single, random blood specimens from CFS patients were obtained from clinics around the country. Thirty-nine percent of these CFS patients were positive for active HHV-6. None of the blood samples from normal controls were positive. The lab believes this to be a significant finding as it demonstrates that active HHV-6 infections in the blood are highly abnormal.

Over a 12 to 18 month period, blood samples were drawn from some of the CFS patients. The study showed that, on average, these samples were positive for active HHV-6 50% of the time. Of the CFS patients who originally tested negative for HHV-6, 16% tested positive on the second testing. ViraCor believes this suggests that the amount of active virus present at different times in the course of an active HHV-6 infection may vary.

It is this belief that has lead Knox and colleagues to conduct repeat testing in cases where the initial sample is negative – something the CDC did not do, and the cause of the vital difference between the testing results.

There are currently three basic methods for detecting the presence of HHV-6 in samples of human tissue and body fluids such as blood and bone marrow: Serology, Polymerase Chain Reaction (PCR) and Virus Isolation. Of these three tests, only virus isolation can detect active, replicating virus and here is why.

Serology

Serologic testing detects the presence of antibodies in the serum. The antibodies, or immunoglobulins, tested for fall into two categories: IgG and IgM. A positive result for IgG indicates a previous infection with HHV-6. Greater than 95% of the population is positive for IgG antibodies, and this result has no correlation to active HHV-6 infections.

Polymerase Chain Reaction

Using samples containing cells, PCR tests the amplification of specific nucleic acid sequences. While these assays are capable of detecting viral DNA, its presence does not indicate an active infection. This test has been found to have a high false negative rate due to inhibitors present in patient samples.

Virus Isolation

There are three methods of Virus Isolation: immunohistochemical staining of tissue samples, PCR assays of cell-free samples and cell cultures. However, only cell culture techniques are considered highly accurate. Classic cell culture techniques require a two to three week incubation period. ViraCor uses a rapid cell culture method that detects only active HHV-6 infections and requires an incubation period of three days. This method detects specific proteins produced only by actively replicating HHV-6.

Source: ViraCor Diagnostic Labs @ www.hhv6.com.

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