The assortment of nasopharyngeal swab (NPS) samples for COVID-19 diagnostic testing poses challenges together with publicity danger to healthcare employees and provide chain constraints. Saliva samples are simpler to gather however may be combined with mucus or blood, and a few research have discovered they produce much less correct outcomes. A group of researchers has discovered that an revolutionary protocol that processes saliva samples with a bead mill homogenizer earlier than real-time PCR (RT-PCR) testing leads to increased sensitivity in comparison with NPS samples. Their protocol seems in The Journal of Molecular Diagnostics, printed by Elsevier.
“Saliva as a pattern sort for COVID-19 testing was a recreation changer in our combat in opposition to the pandemic. It helped us with elevated compliance from the inhabitants for testing together with decreased publicity danger to the healthcare employees throughout the assortment course of,” mentioned lead investigator Ravindra Kolhe, MD, PhD, Department of Pathology, Medical College of Georgia, Augusta University, Augusta, GA, USA.
The examine included samples from a hospital and nursing dwelling in addition to from a drive-through testing website. In the primary section (protocol U), 240 matched NPS and saliva pattern pairs had been examined prospectively for SARS-CoV-2 RNA by RT-PCR. In the second section of the examine (SalivaAll), 189 matched pairs, together with 85 that had been beforehand evaluated with protocol U, had been processed in an Omni bead mill homogenizer earlier than RT-PCR testing. An extra examine was performed with samples with each protocol U and SalivaAll to find out if bead homogenization would have an effect on the scientific sensitivity in NPS samples. Finally, a five-sample pooling technique was evaluated. Twenty constructive swimming pools containing one constructive and 4 destructive samples had been processed with the Omni bead homogenizer earlier than pooling for SARS-CoV-2 RT-PCR testing and in comparison with controls.
In Phase I, 28.3 p.c of samples examined constructive for SARS-CoV-2 from both NPS, saliva, or each. The detection fee was decrease in saliva in comparison with NPS (50.0 p.c vs. 89.7 p.c). In Phase II, 50.2 p.c of samples examined constructive for SARS-CoV-2 from both saliva, NPS, or each. The detection fee was increased in saliva in comparison with NPS samples (97.8 p.c vs. 78.9 p.c). Of the 85 saliva samples examined with each protocols, the detection fee was one hundred pc for samples examined with SalivaAll and 36.7 p.c with protocol U.
Dr. Kolhe noticed that the underlying points related to decrease sensitivity of saliva to RT-PCR testing could possibly be attributed to the gel-like consistency of saliva samples, which made it troublesome to precisely pipet samples into extraction plates for nucleic acid extraction. Adding the homogenization step rendered the saliva samples to uniform viscosity and consistency, making it simpler to pipet for the downstream assay.
Dr. Kolhe and his colleagues additionally efficiently validated saliva samples within the five-sample pooling technique. The pooled testing outcomes demonstrated a constructive settlement of 95 p.c, and the destructive settlement was discovered to be one hundred pc. Pooled testing might be important for SARS-CoV-2 mass surveillance as colleges reopen, journey and tourism resume, and folks return to places of work.
“Monitoring SARS-CoV-2 will stay a public well being want,” Dr. Kolhe mentioned. “The use of a non-invasive assortment technique and simply accessible pattern comparable to saliva will improve screening and surveillance actions and bypass the necessity for sterile swabs, costly transport media, and publicity danger, and even the necessity for expert healthcare employees for pattern assortment.”