Food for thought: Eating before saliva collection and interference with SARS-CoV-2 detection (preprint)

ABSTRACT

Background: Saliva is an optimal specimen for detection of viruses that cause upper respiratory infections including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) due to its cost-effectiveness and non-invasive collection. However, together with intrinsic enzymes and oral microbiota, children's unique dietary habits may introduce substances that interfere with diagnostic testing. Methods: To determine whether children's dietary choices impact SARS-CoV-2 detection in saliva, we performed a diagnostic study that simulates testing of real-life specimens provided from healthy children (n=5) who self-collected saliva at home before and at 0, 20, and 60 minutes after eating from 20 foods they selected. Each of seventy-two specimens was split into two volumes and spiked with SARS-CoV-2-negative or -positive standards prior to side-by-side testing by reverse-transcription polymerase chain reaction matrix-assisted laser desorption ionization time-of-flight (RT-PCR/MALDI-TOF) assay. Results: Detection of internal extraction control and SARS-CoV-2 nucleic acids was reduced in replicates of saliva collected at 0 minutes after eating 11 of 20 foods. Interference resolved at 20 and 60 minutes after eating all foods except hot dog in one participant. This represented a significant improvement in detection of nucleic acids compared to saliva collected at 0 minutes after eating (P=0.0005). Conclusions: We demonstrate successful detection of viral nucleic acids in saliva self-collected by children before and after eating a variety of foods. Fasting is not required before saliva collection for SARS-CoV-2 testing by RT-PCR/MALDI-TOF, but waiting 20 minutes after eating is sufficient for accurate testing. These findings should be considered for SARS-CoV-2 testing and broader viral diagnostics in saliva specimens.