Independent Testing to Accelerate the Development of Lateral Flow Assays for Influenza A, Influenza B and SARS-COV-2

As the test verification core for the Rapid Acceleration of Diagnostics (RADx) Independent Test Assessment Program (ITAP), we conducted independent bench- and field-based performance testing of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza A&B lateral flow assays (LFAs) prior to formal clinical studies for Food and Drug Administration (FDA) submission.

During bench testing, the limit of detection (LOD) was approximated using serially diluted panels of laboratory-propagated virus. In field studies, LFA results were interpreted by study participants, and sensitivity and specificity were determined using reverse transcription polymerase chain reaction (RT-PCR) (Xpert CoV-2/Flu/RSV plus) from a concurrent nasal swab as the reference standard.

Between February 2023 and February 2025, we tested 30 iterations of 14 LFAs. LODs were 53 277-1 393 314 genome equivalents (GE)/mL for SARS-CoV-2, 85 027-1 731 676 for influenza A, and 11 688-2 960 941 for influenza B. Field studies enrolled 27 to 126 participants per LFA with most enrolling at least 50 participants. When minimum 5 positive cases were enrolled, sensitivity ranged from 0.57-1.00 for SARS-CoV-2 and 0.64-0.85 for influenza A. Influenza B case enrollment was low. Specificity ranged from 0.91-1.00 across all targets. Eleven of 14 devices underwent at least two iterations of testing. Following ITAP assessment, 7 devices received FDA emergency use authorization, and 3 ultimately received de novo marketing approval or 510 (k) clearance.

The ITAP enabled rapid feedback to federal agencies and manufacturers on the analytical and clinical performance of over-the-counter LFAs for SARS-CoV-2 and influenza, ultimately contributing to success in regulatory authorization or clearance.