Saliva as a diagnostic specimen for testing respiratory virus by a point-of-care molecular assay: a diagnostic validity study

Abstract

Objectives: Automated point-of-care molecular assays have greatly shortened the turnaround time of respiratory virus testing. One of the major bottlenecks now lies at the step of the specimen collection especially in a busy clinical setting. Saliva is a convenient specimen type which can be provided easily from adult patients. This study assessed the diagnostic validity, specimen collection time, and cost associated with the use of saliva. Methods: This was a prospective diagnostic validity study comparing the detection rate of respiratory viruses between saliva and nasopharyngeal aspirate (NPA) among adult hospitalized patients using Xpert® Xpress Flu/RSV. The cost and time associated with the collection of saliva and nasopharyngeal specimens were also estimated. Results: Between July and October 2017, 214 patients were recruited. The overall agreement between saliva and NPA were 93.3% (196/210, κ 0.851, 95% CI 0.776-0.926). There was no significant difference in the detection rate of respiratory viruses between saliva and NPA (32.9% [69/210] vs 35.7% [75/210]; P=0.146). The overall sensitivity and specificity were 90.8% (81.9-96.2%) and 100% (97.3-100%), respectively, for saliva, and were 96.1% (88.9-99.2%) and 98.5% (94.7-99.8%), respectively, for NPA. The time and cost associated with the collection of saliva were 2.26-fold and 2.59-fold lower, respectively, than those of NPA. Conclusions: Saliva specimen has high sensitivity and specificity in the detection of respiratory viruses by an automated multiplex Clinical Laboratory Improvement Amendments (CLIA)-waived point-of-care molecular assay when compared with that of NPA. The use of saliva also reduces the time and cost associated with specimen collection.