FDA authorizes first COVID-19 test using at-home saliva samples, begins unveiling serological test validation data

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FDA’s authorization of a COVID-19 diagnostic from Rutgers University marks the first time the agency has signed off on detecting SARS-CoV-2 from saliva samples collected at home, which avoids the inconvenience of both in-office visits and invasive swabs.

The May 7 Emergency Use Authorization (EUA) comes on the heels of the first authorization for a CRISPR-based diagnostic, and the publication of the first data from an independent test validation initiative led by NCI.

Rutgers’ reverse transcription polymerase chain reaction (RT-PCR)-based test, which is performed in the university’s high-complexity CLIA lab, can be run on samples self-collected by patients using the Spectrum Solutions LLC SDNA-1000 Saliva Collection Device, in addition to typical nasal or throat swabs.

On April 21, FDA re-issued an EUA for an RT-PCR test from Laboratory Corp. of America Holdings (NYSE:LH) to allow at-home collection of nasal swabs.

An at-home sample collection option could eventually be available for Sherlock Biosciences Inc.’s CRISPR-based test, also authorized May 7 (see “CRISPR Comes of Age”).

Information for use (IFU) documents for the Rutgers test do not include information on the test’s limit of detection (LoD), defined as the lowest amount of the target that the test can detect, at least 95% of the time. The Sherlock test’s LoD is 6.75 genomic copies/μL (6,750 copies/mL), which is in line with the performance of LabCorp’s test, but less sensitive than many RT-PCR tests granted EUA by FDA (see “Pushing Limits of Detection”).

FDA has begun making performance metrics more transparent for another type of COVID-19 assay: serological tests that detect antibody responses to the virus.

For COVID-19 serological tests with EUA, the agency has created a website compiling performance data reported in each test’s IFU document. In cases where a developer reported multiple metrics under different settings, FDA experts selected the results they considered to be most representative of expected test performance.

The reported data also includes the each test’s expected positive predictive value (PPV) and negative predictive value (NPV) for an assumed case prevalence of 5%, since the degree to which a positive or negative result can be trusted depends on the fraction of the population that has been exposed to COVID-19 (see “Good Test Hunting”).

A test from Euroimmun AG, granted EUA on May 4, is the first to report data from an independent study conducted by the NCI-led serological test validation initiative (see “NCI Takes Lead on Serological Test Validation”).

The initiative evaluates test performance using a standardized panel of 30 samples from people infected with SARS-CoV-2, and 80 negative control samples collected before the pandemic. Test developers can seek EUA based on NCI’s validation studies via an FDA “umbrella program” announced April 28.

NCI has shared validation data from at least 13 test kits with FDA. On Monday, FDA increased regulatory scrutiny of serological tests, based in part on data from NCI’s initiative showing some tests that came on the market without regulatory review were performing poorly (see “FDA Tightens Reins”).

Further analysis of the coronavirus crisis can be found at https://www.biocentury.com/coronavirus

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