FDA approves Zimmer's novel diagnostic for detecting infections in orthopedic joint replacements

The FDA has approved a new diagnostic tool to help determine whether swelling around a prosthetic joint replacement is being caused by an infection.

The Synovasure test kit—manufactured by CD Diagnostics, which was acquired by Zimmer Biomet in 2016—takes a sample from the viscous, lubricating fluid that surrounds the joint and searches for antimicrobial proteins released by white blood cells. It is designed for patients being evaluated for surgery to revise or replace a failing implant.

“Prior to today’s 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,” the FDA’s Tim Stenzel, M.D., Ph.D., director of the Office of In Vitro Diagnostics and Radiological Health, said in a statement.

Infections in the fluid surrounding joint replacements can lead to pain, swelling and decreased function and may require surgery for treatment and a new prosthetic implant, the agency said.

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The test does not identify a specific type of infection on its own; the FDA says it’s intended to be used alongside other clinical and diagnostic findings. By detecting the immune system proteins known as human alpha defensins, the Synovasure kit can provide an answer in about 10 minutes compared to the days sometimes required to complete X-ray analyses or lab testing of joint fluid.

“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,” Stenzel added.

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The FDA granted Zimmer Biomet and CD Diagnostics’ kit de novo approval and established new special control criteria for the future review of similar tests, which aim to spot localized infections by detecting non-microbial substances such as proteins released by an immune system response.