Evaluation of the practicability of a finger-stick whole-blood SARS-Cov-2 self-test adapted for the general population

Abstract

Background: COVID-19 (COronaVIrus Disease 2019) is an infectious respiratory disease caused by the novel SARS-CoV-2 virus. Point of Care (POC) tests have been developed to detect specific antibodies, IgG and IgM, to SARS-CoV-2 virus in human whole blood. They need to be easily usable by the general population in order to alleviate the lockdown that many countries have initiated in response to the growing COVID-19 pandemic. A real-life study has been conducted in order to evaluate the performance of the COVID-PRESTO® POC test and the results were recently published. Even if this test showed very high sensitivity and specificity in a laboratory setting when used by trained professionals, it needs to be further evaluated for practicability when used by the general public in order to be approved by health authorities for in-home use.

Methods: 143 participants were recruited between March 2020 and April 2020 among non-medical populations in central France (nuclear plant workers, individuals attending the Orleans University Hospital vaccination clinic and Orleans University Hospital non-medical staff). Instructions for use, with or without a tutorial video, were made available to the volunteers. Two separate objectives were pursued: evaluation of the capability of participants to obtain an interpretable result, and evaluation of the users' ability to read the results.

Results: 88.4% of the test users judged the instructions for use leaflet to be clear and understandable. 99.3% of the users obtained a valid result and, according to the supervisors, 92.7% of the tests were properly performed by the users. Overall, 95% of the users gave positive feedback on the COVID PRESTO® as a potential self-test. Neither age nor education had an influence.

Conclusion: COVID-PRESTO® was successfully used by an overwhelming majority of participants and its use was judged very satisfactory, therefore showing promising potential as a self-test to be used by the general population. This POC test can become an easy-to-use tool to help detect whether individuals are protected or not, particularly in the context of a second wave or a mass vaccination program.

Fig 1. Interpretation of results for COVID-PRESTO^®.

COVID-PRESTO^® uses anti-human immunoglobulin (Ig) M antibody (test line M), anti-human IgG antibody (test line G) and rabbit IgG (control line C) immobilized on a nitrocellulose strip. The Conjugate (recombinant COVID-19 antigens labeled with colloidal gold) is also integrated into the strip. A specimen is added to the sample well (S) followed by addition of assay buffer to the buffer well (B), IgM and/or IgG antibodies if present, will bind to COVID-19 conjugates forming antigen-antibody complexes. These complexes migrate through the nitrocellulose membrane by capillary action. When the complex meets the line of the corresponding immobilized antibody (anti-human IgM and/or anti-human IgG), the complex is trapped forming a burgundy colored band which confirms a reactive test result. The absence of a colored band in the test region indicates a non-reactive test result. To serve as a procedural control, a colored line always changes from blue to red in the control line region, indicating that the proper volume of specimen has been added and membrane wicking has occurred. If the control line does not switch colors, then the test is deemed invalid.

Fig 2. User satisfaction regarding the use of COVID-PRESTO^® as a self-test.

Percentages of participants for each choice of response to the question no.7 of the satisfaction questionnaire.

Fig 3. Participants with an education level 4 or 5 requested assistance more frequently.

Number of participants having asked for a supervisor’s assistance according to education level (* χ² p<0.05 vs. education level 3 and below or level 6 and above).

Fig 4. Description of the execution ratings according to the supervisors.

Number of participants in each rating category according to age (A) or education level (B).

Fig 5. Description of the readability of the test results according to the participants.

Number of participants in each rating category according to age (A) or education level (B).