SARS-CoV-2 disease has as of late risen and quickly spreading in people causing a critical danger to universal wellbeing and the economy. Respiratory specimens have been used to diagnose SARS-CoV-2 infection by Abbott rRT-PCR, and are regarded as the main detection method. Following the rapid global spread of SARS-CoV-2 and the need for universal testing, more and more individuals are exposed to non-inactivated virus samples. The WHO and United States CDC have released laboratory guidelines to mitigate the risk of exposure during diagnostic and research procedures [25–27]. The proceeded require for COVID-19 testing worldwide requires the utilization of straightforward and viable inactivation techniques.
It has appeared that within the SARS-COV-2 swab test, the amount of SARS-COV-2 might be decreased at 60°C for 30min and in bulklysis, but still irresistible. As it was heating at a temperature of 100°C for 10min was able to inactivate it [12].
However, we have been trying to demonstrate that it is possible to ensure the test integrity by applying heat inactivation under several conditions. RT-PCR Ct values are defined as the number of cycles of amplification required for the accumulated fluorescence (produced by target gene amplification) and are inversely related; low Ct values indicate high viral loads and high Ct values indicate low virus NA concentration in the sample [28]. In this study, the Ct value was essentially influenced by warming at 60°C and 100°C for those with weak positive samples. This is in agreement with the studies of Pastorino, (2020) [12]. The less eminent increase in Ct value observed when the virus was heated to 100°C, can be ascribed to the shorter warming time, this can be in line with the study by Zou et al., 2020 [26]. Lower temperature heat treatment combined with chemical inactivation, short-duration high-temperature heat treatments, or chemical inactivation alone may be more suitable to protect RNA integrity and maximize PCR optimization for the discovery of SARS-COV-2 RNA from low-concentration SARS-COV-2 samples. Our results show significant variation in the effect of heat-treatment inactivation on the SARS-CoV-2 detection. This emphasizes the significance of local approval of inactivation strategies and the need for consistency in inactivation protocols.
Weak positive samples may become false negatives in SARS-CoV-2 RT-PCR detection. Our study also has shown that the heat-inactivated samples at 56°C were consistent with those in heat-inactivated ones at 60°C, 100°C, and chemical bulk lysis for low Ct value results, which agrees with the study done by Pastorino, B., 2020, Rao SN., 2020 and Pan, Y., 2020 [12, 29, 30].
Warming at 100℃ for 10min would result in untrue negative, which is steady with that of warming at 92℃ for 15min, the SARS-CoV-2 RNA in a test were dropped altogether as the study done by Zou et al., 2020 and Burton, J., 2021[26, 31]. In reality, considers has been proposed that the test cells should pass on and burst within the occasion of moderately high temperature and long terms, driving to the discharge high number of cell nucleases, and after that, a huge sum of RNA debasement, which may contribute to untrue negative in NA detection. We hypothesize that heating at 100℃ for a long period of time lyse a huge number of cells, and leaves out RNA to RNases enzyme shown within the tests.
Although our study showed that heating at 100℃ for 10min was steady with heat at 56°C, except for those tests with frail positive, strong positive samples appeared an inclination to diminish in Ct values to a few extents, this is in agreement with the study done by Wang, T., 2020 [32]. The RNA conservation may be due to the conservation chemical, which contains guanidine isothiocyanate. This proposed that the nearness of the conservation chemical can viably ensure the keenness of the viral NA, in this manner expanding the extent of recognizable NAs. However, numerous components can impact the effect of the lysis buffer, the amount of virus, nature of the network, contact time, and response temperature, concentration/composition of the lysis buffer used.