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Test Spots Joint Replacement Infections

WEDNESDAY, Aug. 15 -- A new diagnostic test more accurately detects infection in artificial hip and knee joints, which could lead to improved treatment and patient outcomes, U.S. researchers say.

According to the Mayo Clinic team, the new test samples bacteria that adhere to the surfaces of the artificial joints, while the current conventional test involves checking tissue around the artificial joint.

In this study of 331 patients who were having their artificial knee or hip joints replaced due to infection or other causes, the researchers found that the conventional test detected 60.8 percent of infections, while the new test detected 78.5 percent of infections.

The findings are published in the Aug. 16 issue of the New England Journal of Medicine.

"The problem with the conventional method is that you need multiple tissue specimens, because the sensitivity of a single specimen is not good -- in other words, the infection might be missed with just one sample," study leader Dr. Robin Patel, a professor of medicine, said in a prepared statement.

"Another issue is that bacteria normally found on the skin can be picked up on the tissue specimen as it is extracted and passes through the skin, yielding a false-positive result. The same bacteria may actually cause the infection, so doctors can't tell just by the type of bacteria detected whether a patient has an infection or not. If multiple specimens are positive for the bacteria, then this indicates that the bacteria are causing the infection," Patel said.

In the new test, bacteria from the artificial joint are cultured and analyzed.

"If you look at the study, you'll see we found a wide variety of different types of bacteria," Patel said. "This is important to recognize, because it is ideal for the doctors to know what type of infection they are dealing with in order to treat it properly -- this determines what type of antibiotic to give, and, in some cases, what type of surgery to perform."

The Mayo Clinic Office of Intellectual Property holds the patent for the new test.

More information

The U.S. Food and Drug Administration has more about joint replacement.

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Posted: August 2007