FIG 2.

Possible confirmation strategies for Ag-RDT results using a laboratory-based NAAT. Typically, confirmation of Ag-RDT results relies on (i) the recollection of an additional specimen (e.g., NP in VTM) for NAAT testing following a positive Ag-RDT result (orange arrows); or (ii) performing individual paired collections for Ag-RDT and RT-PCR and comparing results of the Ag-RDT and the laboratory-based NAAT (blue arrows). A third strategy was investigated to reduce the need for paired collection, or return for recollection, where NAAT testing is performed directly on RTB following a positive Ag-RDT (green arrows). Ag-RDT, antigen-based rapid diagnostic test; NA, nasal; NP, nasopharyngeal; NAAT, nucleic acid amplification test; RTB, residual test buffer; VTM, viral transport media.