371. Adding sputum and saliva to nasopharyngeal swab samples for PCR detection of Respiratory Syncytial Virus in adults hospitalized with acute respiratory illness may double case detection

Abstract

Background In hospitalized patients, nasopharyngeal (NP) swabs are the most common samples obtained for Respiratory Syncytial Virus (RSV) PCR testing. However, adding sputum is known to increase diagnostic yield, and saliva has been successfully used for viral respiratory infection diagnosis. We sought to compare RSV prevalence detected by PCR testing of NP swab alone versus NP swab plus saliva and sputum in adult patients hospitalized with acute respiratory illness (ARI). Methods This ongoing, prospective cohort study enrolled patients aged ≥40 years hospitalized for ARI in 4 hospitals in Louisville, Kentucky (Season 1: 27 Dec 21 – 1 Apr 22). NP swab, saliva, and sputum samples were obtained at enrollment or scavenged from standard-of-care specimens (all collected ≤3 days of admission), and PCR tested with Luminex ARIES FluA/B/RSV platform. We produced Venn diagrams of RSV positive samples by sample type for all patients and restricted to those with all 3 sample types. RSV prevalence for NP swab alone was calculated as number of patients with RSV-positive NP swabs divided by total number of patients tested. RSV prevalence by NP swab plus saliva and sputum was calculated as number of patients with RSV-positive NP swab, saliva, or sputum samples divided by total number of patients tested. Results We enrolled 653 patients and collected NP swabs (100% of patients), saliva (96%), and sputum (43% overall and 93% of the 303 sputum-producing patients). Among all patients, 28 patients tested RSV positive (Figure 1A), and when restricted to those with all 3 samples (Figure 1B), 14 tested positive. The overall cohort’s RSV prevalence by NP swab alone was 1.8% (12/653) and by NP swab plus saliva and/or sputum was 4.3% (28/653): 2.33 times higher with addition of saliva and sputum samples. Among patients with all 3 specimen types, the RSV prevalence increase was the same, and none were positive by NP swab only. Figure 1.Venn diagrams of positive RSV PCR tests (Left) A. Positive RSV PCR tests for 653 patients in overall cohort (Right) B. Positive RSV PCR tests for 275 patients with all 3 samples obtained. Conclusion RSV was most commonly detected in saliva samples. Current standard-of-care utilizing NP swab for RSV PCR testing appears to underestimate true RSV prevalence in hospitalized adult patients with ARI by more than 2-fold. Disclosures Alan Junkins, PhD, D(ABMM), Biomerieux: Advisor/Consultant Paul S. Schulz, MD, Gilead: Advisor/Consultant|Gilead: Grant/Research Support|Gilead: Honoraria|Merck: Advisor/Consultant|Merck: Grant/Research Support|Merck: Honoraria Robin Hubler, MS, Pfizer Inc.: Employee|Pfizer Inc.: Stocks/Bonds Paula Peyrani, MD, Pfizer, Inc: Employee|Pfizer, Inc: Employee|Pfizer, Inc: Stocks/Bonds|Pfizer, Inc: Stocks/Bonds Paula Peyrani, MD, Pfizer, Inc: Employee|Pfizer, Inc: Employee|Pfizer, Inc: Stocks/Bonds|Pfizer, Inc: Stocks/Bonds Qing Liu, M.S., Pfizer Inc.: I am a full time employee of Pfizer and hold Pfizer stocks Bradford J. Gessner, M.D., M.P.H., Pfizer Inc.: Employee|Pfizer Inc.: Stocks/Bonds Elizabeth Begier, M.D., M.P.H., Pfizer: Employee|Pfizer: Stocks/Bonds.

Adjusting for Case Under-Ascertainment in Estimating RSV Hospitalisation Burden of Older Adults in High-Income Countries: a Systematic Review and Modelling Study

“…We assumed that a combination of sputum, saliva, and nasopharyngeal specimens testing through PCR plus paired serology would be the gold standard. The detection proportion was calculated on the basis of a prospective multi-specimen study that found a 1.6-fold increase in RSV detection adding saliva and sputum specimens to nasopharyngeal swab [ 18 ]. For both steps, we incorporated the innate statistical uncertainty around the testing accuracy studies through a Bayesian approach and sampled 1000 times from the posterior beta distribution of detection proportion based on data and assumed non-informative prior distribution (i.e.…”

“…rapid antigen test), which could also be used for adjusting for case under-ascertainment [ 12 ]; the adjustment did not consider the diagnostic value of a third (or more) diagnostic test or specimen, in addition to paired serology and sputum. Moreover, no studies have evaluated the benefit of adding saliva, which has been shown to be a sensitive specimen type for viral respiratory testing [ 13 , 14 ].…”

The disease burden of respiratory syncytial virus in older adults

“…Older adults often show diminished viral presence, especially if tested late, and generally have lower viral concentrations than children [44]. Broadening testing to include saliva, sputum, and serology have proven more effective [10 ▪▪ ]. A recent study in US has shown that RSV prevalence by nasopharyngeal swab alone was 1.8% but increased to 4.5% when saliva (and sputum) was added [10 ▪▪ ].…”

“…Broadening testing to include saliva, sputum, and serology have proven more effective [10 ▪▪ ]. A recent study in US has shown that RSV prevalence by nasopharyngeal swab alone was 1.8% but increased to 4.5% when saliva (and sputum) was added [10 ▪▪ ]. These data were utilized in the recent meta-analysis by Li et al [8 ▪▪ ] to report that the annual estimates RSV hospitalizations in adults ≥65 years industrialized countries could be as high as 787 000 (460–1347).…”

“…However, a small proportion of cases may result in more severe acute LRTI leading to serious outcomes such as hospitalizations and death [7 ▪ ,8 ▪▪ ]. The incidence rates, however, show marked variability in any given year (across regions and countries) due to factors like inadequate testing and the potentially suboptimal sensitivity of conventional diagnostic specimens and tools in adults [9 ▪▪ ,10 ▪▪ ]. There is also marked variability in RSV activity year on year [5].…”