Validation of dried saliva for molecular diagnostics

A pivotal moment for the development of point of care diagnostics for COVID-19 was the validation of sample types that were alternatives to nasopharyngeal secretions. Specifically, anterior nasal fluid and saliva demonstrated a promising combination of high viral loads and minimal patient discomfort. However, only anterior nasal swabs were widely adopted, in part due to the complexity of saliva, its inherent variability between patients, and lack of a standardized method to collect a quality sample. Herein, we aim to standardize saliva sampling by repurposing FishburneTabs—paper-based tabs originally designed to diagnose dry mouth—as a sample collection tool for viral diagnostics. The workflow for operationalizing dried saliva is aligned with current sample processing methods for dried blood spot cards: (i) a patient collects a saliva sample with a FishburneTab, (ii) the FishburneTab is set on a flat surface to dry, and, after transport to a clinical laboratory, (iii) a standard hole punch is used to acquire punches for analysis. We show that FishburneTabs can reliably collect viral RNA, facilitate long-term dried sample storage, and achieve comparable performance to paired samples of liquid saliva (i.e., 92% accuracy). We validated this approach using a panel of 125 clinical samples, where dried saliva had a sensitivity of 85% and a specificity of 94% compared to paired liquid samples. These results suggest that FishburneTabs can be used to promote decentralized testing of upper respiratory viral infections through the self-collection of dried saliva.