While the data alone isn’t strong enough to rationalize authorization or “other regulatory action” for any given test, the FDA said the data can better inform health care providers, labs and patients on which tests they decide to use.
The data show the tests’ Limit of Detection (LoD). The lower the number, the better, because it suggests the test can detect a lower amount of viral material in a sample and therefore signals a more sensitive test.
As of Sept. 10, the FDA contacted developers of 176 authorized assays for shipping information to send a standardized sample panel provided by the health agency. Of the available data for around 60 tests so far, the LoDs ranged from 540,000 NDU/mL for Quidel Corporation’s Lyra Direct SARS-CoV-2 Assay, to as low as 180 NDU/mL for PerkinElmer’s coronavirus nucleic acid detection kit. NDU refers to nucleic acid-based amplification tests (NAAT) detectable units (NDU).
“By providing this panel to both commercial and laboratory test developers and evaluating the data we receive, we are able to gain valuable insight into the comparative performance of different authorized molecular diagnostic tests under the same conditions,” Dr. Jeff Shuren, director of FDA’s Center for Devices and Radiological Health, said in a news release. “Reference panels can be used in many ways to support test development and authorization, but most importantly, they are a powerful tool in monitoring test performance and ensuring that Americans have access to diagnostics they can trust.”
The FDA previously developed a reference panel to assess diagnostic devices for the Zika virus.
In the case of SARS-CoV-2, officials said the panel has “one heat-inactivated SARS-CoV-2 strain and one heat-inactivated MERS-CoV strain in cell culture media” to confirm the determined LoD for the virus causing COVID-19 and to assess cross-reactivity for the latter.
The panel has five tubes, T1 to T5; T1 has the SARS-CoV-2 strain, while the rest of the tubes have blinded samples. “Although the FDA knows the concentration, the developer testing the samples does not,” officials explained.
Officials also said “recent mutations reported for SARS-CoV-2, which may impact molecular testing, are not included.”
While the data is readily available for nearly 60 tests at the moment, several tests may be of particular interest, like those of Abbott Molecular’s RealTime SARS-CoV-2 assay, Centers for Disease Control and Prevention’ (CDC) 2019-nCoV Real-Time RT-PCR Diagnostic Panel or Eli Lilly and Company’s Lilly SARS-CoV-2 Assay, which returned LoD values of 5,400, 18,000 and 18,000 NDU/mL, respectively.