Cycle threshold responses in SARS-COV2 PCR tests depend on the method by which the samples were obtained and require strict global standardization

Purpose Since 2020, a SARS-COV2 epidemic has been raging worldwide. The cycle of the PCR test in which the virus is detected is called cycle threshold (CT). The method of obtaining the sample is not detailed in any published study and is based on general guidelines of the CDC. Our contention is that the manner in which the sample is obtained has a dramatic effect on CT values. Methods For each person suspected of having Covid-19 who arrives at the emergency room, two swabs are taken in succession, one according to CDC guidelines and the other according to Ziv guidelines. The Ziv method sample collection guidelines determine the depth of penetration, the number of rotations of the swab, and their direction. Each double sample was sent for analysis. Results Analysis of the CT results of the sample to results methods and of the Seegene platform clearly found (p = 0.003 and p = 0.001, respectively) that more rigorous sample collection yielded lower CT values. Conclusion The method of obtaining the samples had a dramatic effect on CT results. Any publication that includes CT results, and certainly studies that discuss CT kinetics, must describe in detail the method by which the samples were obtained. In places where it is also important to detect the onset of illness (airports, hospitals, schools, etc.), it is important to use the Ziv method to reduce the risk of false negatives.

Automated summary

This study examines the impact of sample collection methods on the results of PCR tests. The findings demonstrate that rigorous sample collection methods lead to lower cycle threshold values. Therefore, it is important to prioritize the method of sample collection in places where accurate detection of disease onset is crucial, in order to minimize the risk of false negatives.