Oct. 16, 2007 Scientists in Iowa are reporting development of a new, amazingly sensitive method for identifying the earliest stages of infection with human papilloma virus (HPV), a common virus that can increase the risk of cervical cancer in women. The test also has the potential for early identification of infection with other so-called DNA viruses, which cause a range of diseases that includes genital herpes and hepatitis.
In the study, Edward S. Yeung and colleagues point out that the most sensitive existing test for viral infections has drawbacks. That test is the Nobel Prize-winning polymerase chain reaction (PCR), used to detect DNA in settings ranging from medical labs to crime scenes. PCR requires an initial step in which scientists "amplify," or copy, a DNA sample a thousand-fold before virus detection can begin.
However, amplification increases the risk of false-positives and false-negatives, especially when a sample has even a tiny amount of contaminants. Since over 50 million Pap smears are performed in the United States each year to test for HPV -- the leading cause of cervical cancer -- a fast, simple, accurate diagnosis is essential.
The new method skips the amplification step entirely, and yet can detect the presence of less than two copies of HPV per cell -- a level corresponding to very early infection. The technique, called single-molecule spectroscopy, could be easily integrated into the Pap smear method. "It can become a good clinical screening or quantification method for viral DNA in cells," opening the door to improved screening tests for hepatitis B, herpes and other diseases.
Article: "Single-Molecule Detection of Surface-Hybridized Human Papilloma Virus DNA for Quantitative Clinical Screening" Nov. 1 issue of Analytical Chemistry.
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