FDA trial regulation of laboratory developed tests (LDTs): An academic medical center's experience with Mpox in-house testing

The 2022 mpox outbreak presented a familiar challenge to clinical laboratories. Accordingly, our institution was able to swiftly implement in-house mpox testing to meet the imminent diagnostic needs of the public health emergency. While the FDA authorized laboratory-developed tests (LDTs) for lesion specimens, however, it restricted the testing of rectal swabs despite mounting evidence of its clinical utility. Notably, within the short timeframe when rectal testing was available, we identified a high-risk patient without apparent lesions who tested monleypox-positive only by our in-house rectal swab assay. In order for our institution to continue testing non-lesion samples, The FDA required a separate Emergency Use Authorization (EUA) application that demanded additional resource-costly validation studies despite utilizing the same testing platform as lesion samples. Here, we provide a brief review of the history, current status, and legal scope surrounding LDT validations, with an in-depth comparison of the technical requirements by CLIA, CAP and the FDA. Importantly, we provide our experience with the mpox EUA submission process to serve as context for the challenges that may be imposed by the new FDA regulations. We hope that our experience will offer a valuable perspective that promotes constructive discourse towards addressing the imperative to offer high-quality laboratory diagnostics without compromising on the need of the medical laboratory community to provide effective patient care.