Because Results Matter
On May 4, 2020, the FDA required all manufactures of SARS-Cov-2 serology assays to file for a EUA. VidaCheck utilizes the serological assay developed and manufactured by Quansys Biosciences. Quansys submitted their EUA to the FDA on May 14th. The results of the validation are shown below.
VidaCheck COVID-19 Antibody Test
FDA Requirement: ≥75 known negative samples with a specificity of >98% (if specificity is not >98% additional cross-reactivity testing is required)
Quansys Result: Quansys has tested 542 negative samples with a specificity of 100%.
Note: Although mutations in the SARS-CoV-2 genome have been identified as the virus has spread, no serologically unique strains have been described relative to the originally isolated virus (this research is exceptionally limited at present). No reactivity testing is recommended for serology assays.
Clinical Agreement Study
FDA Requirement: At least 30 specimens collected from patients that have been previously confirmed infected by a SARS-CoV-2 by a PCR test and at least 75 negative samples should demonstrate a minimum 90.0% positive percent agreement and overall 95.0% negative percent agreement.
Quansys Result: At this point Quansys has tested 34 confirmed positive samples and 542 negative samples with 97% PPA (sensitivity) and 100% NPA (specificity).
FDA Requirement: If a claim for fingerstick is desired, we believe evaluating a minimum of 30 positive and 30 negative fingerstick whole blood samples may be acceptable to demonstrate clinical performance in fingerstick samples.
Quansys Result: Quansys Result: 31 positive samples and 32 negative samples were collected using fingerstick collection devices with results of 97% PPA (sensitivity) and 100% NPA (specificity).
*Fingerstick evaluation method of testing is not available at this time.
FDA Requirement: If your test is intended for the detection of total antibody with no differentiation between different immunoglobulins, then this study does not apply.
Quansys Result: Quansys screened the SARS-CoV-2 kit reagents on plates coated with IgG, IgM, IgA, IgE, and IgD. Only reactivity with IgG class antibodies were observed.
What PPA, NPA, and PPV Values Represent When Evaluating COVID-19 antibody tests.
Sensitivity (PPA) = Positive Percent Agreement. Suppose that a population who developed antibodies after being exposed to the COVID-19 virus received an antibody test. The percentage of that population who test positive for antibodies is the PPA. A test with low PPA tells people that truly have antibodies that none are present.
Specificity (NPA) = Negative Percent Agreement. Suppose that a population was never exposed to COVID-19 and therefore never developed antibodies. The percentage of that population who test negative is the NPA. A test with low NPA tells people that they have antibodies when none are truly present.
PPV = Positive Predictive Value. Suppose that a population tested positive for antibodies. The percentage of that tested population who truly have antibodies is the PPV. A test with low PPV says that antibodies are detected when none are truly present (false positive). Higher PPV means higher confidence in a positive result.
For example: Using a PPV of 99.7% as an example, one can assume that for every 1,000 positive test results, that 3 of them are false positive.
In the context of COVID-19, false positive results are especially concerning. Although time will tell whether the presence of COVID-19 antibodies indicates immunity, for many other diseases the presence of antibodies indicates a level of immunity. For such diseases, false positive antibody test results may cause an individual to modify their behavior and put themselves and potentially others at unnecessary risk for disease. Antibody tests with high PPV prevent such situations from occurring. When selecting an antibody test, patients should choose tests with high PPV.
How Does the VidaCheck COVID-19 Antibody Test Compare to Other COVID-19 Antibody Tests on the Market?
Information collected from the U.S. Food & Drug Administration website, FDA.gov. Information current as of 05/13/2020.
PPV = 99.7
333 positive test results with 1 false positive.
Individual did not have COVID-19 and tested positive for antibodies.
Individual had COVID-19 and tested positive for antibodies.
Biotech Company 5
PPV = 55.2
333 positive test results with 149 false positives