NEW YORK – On Wednesday, Cellex became the first firm to receive Emergency Use Authorization from the US Food and Drug Administration for a coronavirus serology test. The assay, which resembles a pregnancy test, is authorized for use in laboratories certified under CLIA to perform as moderate- and highly-complexity tests.
Called the qSARS-CoV-2 IgG/IgM Rapid Test, the Cellex test is a lateral flow immunoassay to detect IgG and IgM in blood serum, plasma, or venipuncture whole blood specimens from patients suspected by a healthcare provider of COVID-19 infection. Results can be read from the test device after approximately 15 minutes according to the instructions for use, and labs must report positive results to public health authorities.
The levels of IgM in a patient's blood begin to rise to detectable levels a few days after infection, while IgG levels become elevated later. Positive results for both IgG and IgM could occur after infection and be indicative of acute or recent infection.
The FDA has guided in its "Policy D" that serology tests that are not intended for sole diagnosis do not need only to notify the agency prior to marketing in the US and do not need to come through the EUA process. However, it has also guided that manufacturers claiming a test can be used as a sole diagnostic should come submit an EUA.
The test's clinical validation, as noted in the IFU, involved 98 positive serum or plasma samples collected from individuals who tested positive with a RT- PCR method for SARS-CoV-2 infection who exhibited mild or no clinical symptoms and 180 negative serum or plasma samples collected prior to September 2019.
Of the 98 positive samples, 91 were positive with IgG or IgM or both. Of the 180 negative samples, 174 were negative.
Another 30 samples were collected from hospitalized individuals who were clinically confirmed positive for SARSCoV-2 infection and exhibited severe symptoms. These samples, along with 70 negative serum or plasma samples, were tested with the qSARS-CoV-2 IgG/IgM Rapid Test. Of the 30 positive samples, 29 were positive with IgG or IgM or both. Of the 70 negative samples, 65 were negative.
Taken together, the qSARS-CoV-2 IgG/IgM Rapid Test had a 94 percent positive percent agreement and 96 percent negative percent agreement.