B-192 Covid on the PCR Pro: a consumer-friendly PCR test
Authors: Garey D , Jones A , Evergreen K , Smith M , Parkinson A , Buccilli M , Cummins J , Wold K , Staker A , Mangum B , Garcia M , Okpebri S , Woodhouse L , Norman J , Edwards Barnett M , Gottfried-Lee I , Durrant K , Young V , Young N , Thurston c , Shehabi Z , Poritz M , Abbott R , Nielsen D , Rejali N 
Published: October 2024

Abstract

Background
The emergence of COVID-19 highlighted the need for rapid and accurate diagnostic solutions that can be deployed on a broad scale. The complexity and long turn-around-time of PCR testing typically performed in molecular laboratories is not compatible with community-wide screening. To overcome these challenges, we present the Co-Dx PCR Pro™, a rapid and simple test platform developed for self-collection and at-home use. The instrument is controlled from the user’s smartphone or tablet and performs sample treatment, RT-PCR, and DNA melting analysis. An automatic calling algorithm provides a simple, “Detected,” or, “Not detected,” result. We demonstrate the utility of this platform using a test for the detection of SARS-COV-2.

Methods
A self-collected anterior nasal swab sample and 2 mLs of water are added to the collection cup. Closing the lid of the cup initiates rehydrating a dried Proteinase K mixture to digest proteins in the sample. After a brief Proteinase K heat-kill step, the instrument mixes the sample with a dried PCR master mix. Primers target two SARS-COV-2 specific genes (RdRp and E gene) and the human RNase P gene as a control. The sample undergoes an RT step followed by 45 cycles of PCR and DNA melting analysis. Detection is by an automatic calling algorithm that identifies a SARS-COV-2 amplicon melting peak at 82°C and RNase P peak at 87°C. The total runtime is less than 30 minutes. The limit of detection for the assay was assessed by contriving intact virus in negative sample matrix, which was then applied to dry swabs. In addition, frozen and banked clinical samples were tested using the Logix Smart®™ Covid-19 test as a comparator assay. A third party performed a usability assessment by having (1) naïve users follow the instructions and self-administer the test (2) expert trained users perform an independent assessment of the assay. Participants were then asked to complete a usability assessment.

Results
The 95% limit of detection was 2,100 copies/swab using contrived nasal swabs. Clinical samples were blinded to the operator and run on the platform. All samples resulted in a diagnosis concordant with the comparator assay. The usability assessment was performed by six naïve users and resulted in a systems usability scale score of “Best” (84.2 ± 14.3, out of 100). The two expert users determined an 80% limit of detection of 700 genome equivalents and “ease of use,” and “satisfaction,” scores of 4.5/5.0 and 5.0/5.0, respectively.

Conclusions
Performance of the PCR Pro platform is on par with laboratory-based PCR testing. The benefits of our assay are its speed and the low complexity platform accessible to the lay. This platform could improve access to molecular diagnostic testing, including use at home. Future expansion to include common respiratory pathogens (Flu, RSV, Strep) will increase utility. Additionally, anonymized results can be aggregated and provide a wealth of epidemiological information at the community level to better inform public health initiatives and health outcomes.