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Aug 6, 2023Keywords:
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Effect of thermal inactivation of biological specimens on the limit of detection of RT-PCR in the diagnosis of SARS CoV-2
Abstract
Background: Coronavirus disease 2019 (COVID-19) is characterized as a global pandemic by World Health Organization. For the safety of medical laboratory personnel and the environment, thermal inactivation of clinical samples is a common practice performed by most laboratories before nucleic acid extraction. However, there are conflicting reports in the literature regarding the effect of thermal inactivation on the analytical sensitivity of molecular assays.
Objective: To test the impact of thermal inactivation using alternative methods on the analytical sensitivity of respiratory samples.
Method: We compared the impact of thermal inactivation of biological samples after adding lysis buffer at 720C for 10 minutes by dry heat block and water bath on analytical sensitivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2). Furthermore, we tested the effect of the thermal inactivation method at 560C using a water bath on the detection rate of SARS-CoV2.
Result: All samples tested positive in dry heat block was also tested positive in the water bath. We observed a similar viral detection rate of viral RNA at 560C for 15 min and 30 min, whereas inactivating samples at 560C on the water bath for 45 minutes drastically reduces the virus detection rate by 20%.
Conclusion: Water bath is not inferior to dry heat block to treat samples with lysis buffer, and can be used instead of dry heat block in district laboratories. However, the inactivation of samples at 560C over 30 minutes drastically reduces the virus detection rate. Hence, samples shall not be heat-treated before nucleic acid extraction.
