A Comparison of Respiratory Syncytial Virus (RSV) Viral Loads Between Nasopharyngeal and Mid-Turbinate Swabs From Children <24 Months With RSV Infection

Abstract

Background. Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis and pneumonia in infants and children. Diagnosis of RSV can be made by molecular detection of RSV in a swab of respiratory secretions. Nasopharyngeal (NP) swabs are the most frequent swab type validated for the detection of RSV, and are often considered the “gold standard” for quantification studies. However, NP sampling is invasive and uncomfortable. We sought to determine whether a less invasive method, a mid‐turbinate (MT) swab, was comparable to NP sampling for quantification of RSV in children. Methods. We prospectively enrolled children <24 months hospitalized at Primary Children's Hospital (Salt Lake City, UT) with a confirmed diagnosis of RSV. Both an NP and MT swab were collected from each infant from different nostrils; subjects were randomized (1:1:1:1) as to the order of collection (left/right nostril first with MT/NP swab first), and parents were asked which collection method (NP versus MT) they preferred after collection. Viral loads were measured by real‐time RT‐qPCR. The correlation between the viral loads generated from the MT and NP swabs was examined. A paired two‐sample t‐test was used to evaluate the difference between viral loads obtained from the MT and NP swabs. Results. Swabs were collected from 30 infants, with a median age of 240 days [range 1‐527]. Four infants had swabs collected on multiple consecutive days. The median (Q1,Q3) duration of symptoms prior to enrollment was 5 days (4,7) and the median (Q1,Q3) hospital stay length was 2 days (1,4). One infant was RSV negative according to the RT‐qPCR assay. The mean (SD) viral loads were similar; 7.24 (1.7) and 7.01 (1.8) log10 copies/mL for 34 paired NP and MT swabs, respectively, with p = 0.59; see Figure 1 for median, range and quartiles. The correlation coefficient between the paired viral loads was high (0.88); see Figure 2 for scatter plot. Most parents (19/24 [79%]) who watched the swabbing preferred the MT swab to the NP swab. Conclusion. MT swabs perform as well as NP swabs for the quantification of RSV in infants. MT swabs are less invasive and preferred by parents for sampling. MT swabs have the potential to replace the NP swab as the “gold standard” for quantitative respiratory viral sampling. (Figure Presented).