Evaluation of a two-stage testing algorithm for the diagnosis of respiratory viral infections

Abstract

New on-demand multiplex molecular respiratory viral diagnostics offer superior performance although can be expensive and some platforms cannot process multiple specimens simultaneously. We performed a retrospective study reviewing results of patients tested for respiratory viruses following introduction of a two-stage testing algorithm incorporating an initial screen with Sofia® immunoassay then secondary Biofire Filmarray®, and compared to a period when only Filmarray® was used. Of 2976 testing episodes, 1814 underwent initial Sofia® then follow-up FilmArray®. A diagnosis of influenza was made by Sofia® in 282 patients, and by FilmArray® in an additional 163 (median time to result 1.12hours versus 3.46hours, P<0.001). Significantly more patients received their diagnosis within 90minutes in winter despite testing more samples (11.1% versus 3.4%, P<0.001), and approximately $36,000 was saved. An algorithmic approach to respiratory viral diagnosis can combine the advantages of accuracy and speed and be cost saving.

Keywords: Diagnosis; Influenza; PCR; Respiratory viral infection.

Fig. 1

Diagram illustrating breakdown of testing performed and results obtained over the study period. PCR, polymerase chain reaction. RSV, respiratory syncytial virus. *Two patients tested positive for both Influenza A and RSV by Sofia®. ^16 cases positive for RSV by FilmArray® were Sofia® negative, the remaining 71 did not undergo RSV testing by Sofia®. Five were positive for both influenza and RSV by FilmArray®.

Fig. 2

Time to final result represented on a Kaplan–Meier cumulative incidence curve (A) comparing summer months using Biofire FilmArray® only to the winter 2-stage approach, and (B) patients during the winter who reached their final diagnosis by Sofia® compared to Biofire FilmArray®. P-values reflect log-rank test results.