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Click here to read about Saliva not a useful diagnostic specimen in children with COVID-19.

A review by KK Women’s and Children’s Hospital (KKH) has found that buccal swabs on their own are not good screening specimens for SARS-CoV-2 in children. The review of daily nasopharyngeal and bilateral buccal swabs taken for 11 children with laboratory-confirmed COVID-19, found that the buccal specimens contained substantially lower viral loads compared with nasopharyngeal specimens. Six children were asymptomatic; five were symptomatic and had a mild course of illness.

Saliva may not be a major route of viral transmission

Saliva can be a potential route of viral transmission in children, especially in infants who tend to drool and place objects in their mouth. To elucidate the viral shedding pattern in buccal specimens of children in order to predict the routes of viral transmission, KKH researchers conducted a study to evaluate the presence of SARS-CoV-2 in buccal specimens in 11 infected children.

COVID-19 was detected from at least one buccal specimen in nine of 11 children (81.8%).

“Our findings confirm that COVID-19 can be detected in the buccal specimens of infected children, and that the viral load is highest in the first week of illness or diagnosis. This suggests a high possibility that, as with adults, the virus is present and potentially transmissible via the saliva of children,” shares corresponding author, Dr Kam Kai-Qian, Associate Consultant, Infectious Disease Service, KKH.

“However, in our study, the average viral loads of buccal COVID-19 were consistently lower than the respective nasopharyngeal specimens, with substantial differences between the average cycle threshold values (Figure 1). Thus, saliva may not be a major route of viral transmission for COVID-19.”

Figure 1: Nasopharyngeal and Buccal SARC-CoV-2 Cycle Threshold Trend for Asymptomatic and Symptomatic Paediatric Patients

Lower viral loads and poorer sensitivity in buccal specimens 

The team also found that the sensitivity of buccal swabs compared with nasopharyngeal swabs ranged from 25 per cent to 71.4 per cent on different days of collection during the first week of illness/diagnosis.

"In view that the buccal specimens yielded substantially lower viral loads and had poor sensitivity compared with nasopharyngeal specimens, buccal swabs do not appear to be a good screening modality for COVID-19, nor a good alternative to document viral clearance in infected children," shares co-author Associate Professor Thoon Koh Cheng, Head and Senior Consultant, Infectious Disease Service, KKH.

"Although there are advantages with buccal specimen collection compared with nasopharyngeal swabs, nasopharyngeal and oropharyngeal swabs remain the recommended upper respiratory tract specimens for detection of COVID-19."

Read the full study here.