10/16/2020 | News release | Distributed by Public on 10/16/2020 10:02
What was the result?
On October 2, a pool containing one of the cohort's saliva sample yielded a very weak signal for one of the two COVID-19 targets. Detection of the weak signal occurred after 38 PCR cycles, (if a signal is not seen within 40 cycles on our assay, the sample is presumed negative). Putting this in perspective, 38 cycles correlates to a signal amplification of 275 billion times for any signal present in the sample pool.
We next examined the individual saliva samples comprising the pool in isolation to confirm the positive reading, per CDC guidance. Each individual sample was tested in triplicate. Only one individual sample yielded any indication of SARS-CoV-2 but the signal was again quite weak and inconsistent in the triplicate results.
We requested a fresh pool of samples from the same 5 individuals 24 hours later and detected signal for both viral amplicons at an amplification that was 4,000 times less than the prior signal, indicating a very large increase in viral load within one day. Upon detection of the positive pool, the 5 members of the pool were referred to a physician for individual diagnostic testing and quarantined. Meanwhile we disambiguated (deconvoluted) the pool and identified virus in a single individual's sample, who subsequently exhibited symptoms of COVID-19 within 3 days. Daily pooled surveillance tests of the remaining cohort for the following 12 days did not yield any positives, indicating the infection was likely contained by the quick action enabled by surveillance testing.