FDA OKs First Diagnostic Test for Prosthetic Joint Infections

Megan Brooks


May 24, 2019

The US Food and Drug Administration (FDA) has approved the first test to help detect periprosthetic joint infection in the synovial fluid of patients being evaluated for revision surgery.

The Synovasure Lateral Flow Test Kit (CD Diagnostics Inc) detects human alpha defensins in the synovial fluid of patients who have undergone total joint replacement. The test takes about 10 minutes to perform. Alpha defensins are antimicrobial proteins released by activated neutrophils in response to infection.

The Synovasure Lateral Flow Test Kit is intended as an aid in determining whether an infection is present in synovial fluid. It does not identify a specific type of infection, the FDA said. Results from the test should be used in conjunction with other clinical and diagnostic findings to aid in diagnosing prosthetic joint infection.

In approving the test, the FDA reviewed data from a clinical study that analyzed 305 prospective synovial fluid samples collected from individuals who had undergone total knee or hip joint replacement and who were being evaluated for revision surgery. The study showed that 89.5% of patients who were diagnosed as having an infection using standard-of-care criteria also tested positive for alpha defensin using the Synovasure test kit.

"Prior to [this] authorization, there were no FDA-authorized diagnostic tests specifically designed to help health care professionals determine whether the inflammation around a prosthetic joint was due to an infection or another cause," Tim Stenzel, MD, PhD, director of the Office of In Vitro Diagnostics and Radiological Health in the FDA's Center for Devices and Radiological Health, said in a news release.

"With this test, health care professionals now have an additional option available to aid their clinical assessment as to whether the patient has an infection and requires revision surgery. Whereas before, surgeons may have opted for surgery when the presence of an infection was unclear, with this test, they have more information and could potentially reduce patient risk by avoiding unnecessary revision operations for replacement joints," said Stenzel.

The FDA reviewed data for the Synovasure Lateral Flow Test Kit through the de novo premarket pathway, a regulatory pathway for some low- to moderate-risk devices of a new type. Along with this marketing authorization, the FDA is establishing "special controls" designed to provide a "reasonable assurance of safety and effectiveness for tests of this type," the agency said.

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