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Midturbinate swabs comparable to nasopharyngeal swabs for detecting RSV in infants
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Midturbinate swabbing was found to be as effective as standard nasopharyngeal swabbing in detecting respiratory syncytial virus in infants, and was preferred by most parents, according to a study published in the Journal of the Pediatric Infectious Diseases Society.
“The diagnosis of respiratory syncytial virus (RSV) infection in infants is frequently made by testing secretions from a nasopharyngeal (NP) swab,” Anne Blaschke, MD, PhD, an associate professor and Edward B. Clark II Endowed Chair in Pediatrics at the University of Utah School of Medicine, told Infectious Diseases in Children. “While NP swabs are the most common type of swab approved for the diagnosis of RSV, NP sampling is invasive and uncomfortable for the child, as well as distressing for the caregiver. A less invasive sample type is desirable for RSV diagnosis and monitoring.”
Blaschke added that “previous studies have shown that sampling from the midturbinate (MT) of infants is similar in sensitivity to an NP swab for the qualitative detection of RSV disease, but it is unknown how quantitative RSV viral loads compare between NP and MT swabs. In our study we investigated whether the less invasive MT swab was comparable to NP sampling for quantification of RSV viral load in infants younger than 24 months hospitalized with RSV.”
Blaschke and colleagues studied infants admitted to Primary Children’s Hospital in Salt Lake City, Utah, during the 2016 and 2017 RSV seasons. Parents rated the severity of the child’s RSV infection using the single-question Patient Global Impression of Severity score, modified for caregivers of infants with RSV. The researchers reported that both NP and MT swabs were taken from each infant, with the order of selection of left or right nostril randomly assigned.
The researchers collected swabs from 84 infants (median age, 4 months) during the study period. Mean viral loads were similar between the two swab collection procedures (7.34 and 7.09 log10 copies/mL for 77 paired NP and MT swabs with positive results, respectively.).
Eighty-one percent of parents had rated their child’s disease as mild or moderate, whereas 13% rated the disease as severe. Among the 65 parents who watched the infant swabbing, 74% definitely preferred MT to the NP swab.
“Our study showed that MT swabs perform as well as NP swabs for the PCR-based quantification of RSV in infants,” Blaschke said. “Additionally, the less invasive MT swabs are preferred by parents for sampling. Our study suggests that MT swabs have the potential to replace the NP swab as the ’gold standard‘ for quantitative viral diagnostics.” – by Bruce Thiel
Disclosures: Blaschke reports receiving funding for this investigator-initiated research from Gilead Sciences Inc. She reported collaborating with BioFire Diagnostics, LLC on federally funded studies and having intellectual property licensed to BioFire Diagnostics, for which she receives royalties through the University of Utah. She reports receiving research funding from BioFire Diagnostics for investigator-initiated research and acting as a paid advisor to BioFire Diagnostics. Please see the study for all other authors’ relevant financial disclosures.
Perspective
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H. Cody Meissner, MD
The diagnosis of RSV respiratory tract infection of infants and young children has undergone a dramatic evolution in the past 2 decades. Initially, cell culture techniques were the basis of a laboratory diagnosis of RSV infection, but this approach required a specialized laboratory and required several days of incubation before cytopathic changes caused by RSV (syncytia formation) could be observed. Centrifugation-enhanced, shell vial techniques shortened the time to results to 24 to 48 hours. Rapid diagnostic techniques took advantage of the large amount of RSV antigen shed in nasal secretions of an infected infant, enabling the development of fluorescent antibody techniques that detected RSV in less than 12 hours, although the sensitivity of these assays varied. Molecular diagnostic techniques using reverse transcriptase-PCR assays have largely replaced both culture and antigen detection. Although expensive, heteroduplex assays can now rapidly and reliably diagnose most pathogens that cause respiratory tract disease in a symptomatic child.
Blaschke and colleagues report that molecular techniques reliably detect and quantify the amount of RSV nucleic acid in swabs obtained from the nasal mucosa of an infected child. Traditionally, NP swab samples have been used to obtain a specimen for testing. This paper demonstrates it is possible to avoid the uncomfortable procedure of obtaining a NP swab and instead use a less invasive sample obtained from the MT area or even the anterior nasal mucosa. The authors report the amount of RSV (viral load) detected in a MT swab was similar to that detected in an NP swab.
The authors explored the relationship between viral load in the upper respiratory tract and disease acuity but found only a limited correlation between initial viral load and days of symptoms before admission of infants with a mean age of 6.8 months and a mean duration of RSV symptoms of 6.1 days before enrollment. Possibly, assessment of viral load at an earlier time point in the illness would offer a better correlation. Whether viral load from secretions obtained from the lower respiratory tract has a better correlation with disease severity is an area of investigation.
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