FDA has expanded the labels of four Lyme disease diagnostics to facilitate the use of a new testing paradigm.
Zeus Scientific secured the clearances after convincing FDA that using enzyme immunoassays (EIA) alone is as accurate as the current two-tiered approach, which uses a Western blot test to confirm the original assay result.
- The low sensitivity of the two-tiered approach has pushed researchers to work on new ways of confirming a Lyme diagnosis, leading Zeus to create an EIA-based method it claims detects 30% more acute cases of the disease than the current approach.
The current two-tiered method to diagnosing Lyme disease came to prominence in the 1990s as a way to compensate for the limitations of EIA tests. Antigen cross-reactivity can cause misdiagnosis of Lyme by EIA tests, necessitating the use of a second confirmatory step. The superior specificity of the Western immunoblot led public health officials to designate it as the second confirmatory test.
That decision reduced the rate of false positives but created a new set of problems. Immunoblots are more subjective and less sensitive than EIA tests, particularly soon after infection when the antibody response to the pathogen is still developing.
In 2011, researchers showed replacing the immunoblot with a second EIA test improved specificity and CDC has expressed an interest in alternatives to one or both steps of the current process. Yet, the lack of regulatory clearances for diagnostics used in modified two-tiered testing (MTTT) systems meant the standard STTT remained the default option.
“We envisioned a similar MTTT concept more than ten years ago, but were unable to convince regulators of this powerful concept at that time,” Zeus CSO Mark Kopnitsky said in a statement. “Since then, many other accomplished researchers have repeatedly demonstrated that the MTTT algorithm is clinically more sensitive, yet equally as specific as the STTT algorithm.”
Zeus claims its MTTT approached “detected up to 30% more acute Lyme disease cases relative" to the standard method. Such an improvement would increase the timely diagnosis of the disease, enabling patients to get treatment sooner.
FDA said Zeus’ approach is “as accurate as current methods,” adding that it is “easier to interpret by a clinical laboratory.” Laboratories can run Zeus’ EIA tests in-house using an automated workflow and generate less subjective results than when using immunoblots.