Evaluation of the EasyNAT SARS-CoV-2 assay PCR test for the diagnosis of SARS-CoV-2 infection

Reverse transcription polymerase chain reaction (RT-PCR) tests are commonly utilized in commercial settings but pose challenges due to labor-intensive procedures and extended response times during peak demand. In contrast, real-time fluorescence and isothermal amplification assays using Crossing Priming Amplification (CPA) offer faster genetic material analysis, eliminate subjectivity, and require less manipulation and personnel training.

This study aimed to validate the EasyNAT SARS-CoV-2 Assay, a diagnostic kit based on CPA, using oral and nasopharyngeal samples. The EasyNAT kit was compared to the Xpert Xpress SARS-CoV-2 kit, evaluating 873 samples obtained during routine analysis at the Microbiology Laboratory of the Hospital Costa del Sol (Marbella, Spain).

The overall sensitivity and specificity for the EasyNAT SARS-CoV-2 Assay were 79.1% (95%CI 74.5–83.7) and 99.5% (95%CI 98.7–100), respectively; with, validity index of 91.9%, positive predictive value of 98.9%, negative predictive value of 88.9%, positive likelihood ratio of 144.5, negative likelihood ratio of 0.21 and a total Youden Index of 0.79. Notably, sensitivity improved in fresh samples (91.4%), along with a high Youden Index (0.91).

The EasyNAT SARS-CoV-2 Assay achieved a higher percentage of concordance in positive samples with Xpert Xpress SARS-CoV-2 when analyzing cycle threshold (Ct) intervals below 30 compared to intervals equal or greater than 30, and demons.

In conclusion, the EasyNAT SARS-CoV-2 Assay demonstrated high sensitivity and agreement with Xpert Xpress SARS-CoV-2, particularly in fresh samples or when the signal was detected at Ct intervals below 30, indicating higher viral loads. This makes it suitable for rapid screening in various settings, including those with limited access to conventional molecular laboratory setting.