Adding a Specimen Type to PCR Testing Demonstrates an Increase in RSV Diagnosis


A new study that went beyond the current standard of testing for the respiratory virus resulted in greater incidence rates and a truer accounting of case loads.

In hospitalized adult patients, RSV diagnosis is typically assessed on PCR testing using nasopharyngeal (NP) swabs. This can be problematic for 2 reasons explains Elizabeth Begier, MD, MPH, senior director, scientific affairs lead, RSV Antiviral/Adult Vaccine Program, Pfizer Vaccines.

“The two primary challenges are first that RSV is actually infrequently tested for, and then second is that the viral loads in the secretions of adults are lower than those in children and that can make picking up RSV—when it's tested for—difficult in the current standard of care for testing,” Begier said.

A new study presented at IDWeek looked at adding a specimen type to see if it would capture greater incidence rates for RSV in adult patients. Investigators performed a prospective cohort study of patients aged ≥40 years and hospitalized for acute respiratory illness (ARI) across 4 hospitals in Louisville, Kentucky during 2 seasons: 2021–2022 and 2022–2023. The investigators utilized NP swab, saliva, and sputum specimens, and PCR tested with Luminex ARIES platform. Virus prevalence was calculated for diagnosis by NP swab alone, and NP swab plus sputum and/or saliva.

They enrolled 2798 patients and collected NP swabs in 100%, saliva in 99%, and sputum in 31% of patients. Of the patients, 133 (4.8%) had RSV diagnosed by any specimen versus 80 (2.9%) diagnosed by NP swab alone, consistent with an 66% increase in prevalence.

“Among 856 patients with three specimens obtained, 62 (7.2%) patients were diagnosed by any specimen, versus 37 (4.3%) patients with RSV diagnosed by NP swab alone. RSV detection trended higher among men (2.00), middle-aged adults (2.03; 40–65 years), and immunocompromised persons (1.78),” the investigators wrote.

As an infectious disease epidemiologist, Begier would like to see a truer accounting for case loads as it might help to address the scope of of the health issue more accurately including the resources and therapeutic availability for patients.

“The existing epidemiologic literature is based on the use of nasal or nasal pharyngeal swab in older adults. Those estimates, because they're based on a single specimen for operational ease, are not accounted for in the full burden of RSV,” Begier said. “And so, from an epidemiologic perspective, really those estimates should be adjusted—for what would be the gain if you had included those additional specimen types.”


Begier E, Ramirez J, et al. Respiratory Syncytial Virus (RSV) Diagnoses in Hospitalized Patients Increases when Additional Specimen Types are Added to Nasopharyngeal Swab: Results from the RSV in Adults Multispecimen Study. Presented at: IDWeek 2023. October 11-14, 2023; Boston, MA. Poster 1019

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