Last modified: 2021-03-05
Abstract
Fekadu Alemu, M.Sc.1*, Getachew Tesfaye Beyene, Ph.D.1*, Eyerus Selomon, B.Sc1, Zewudu Selomon, B.Sc1, Sinknesh Wolde, M.Sc1, Desalegn Abeje Tefera, B.Sc1, Dawit Hailu Alemayehu, M.Sc1, Alemseged Abdissa, Ph.D1, Andargachew Mulu, Ph.D1.
*these authors contributed equally
1Armauer Hansen Research institute, Jimma Road ALERT Compound, P.O. Box address 1005, Addis Ababa, Ethiopia
Abstract
Background: coronavirus disease 2019 (COVID-19) has engulfed the world and was characterized a global pandemic by world health organization. For the safety of medical laboratory personnel, heat inactivation of clinical samples is a common practice performed by most laboratories before testing. However, in resource limited countries, the availability of standard laboratory equipment used for heat inactivation is limited, which forced many laboratories to find alternative approaches. The aimof the study is to test the impact of heat inactivation on the analytical sensitivity of respiratory samples.
Methods: we compared the impact of heat treatment at 720C for 10 minutes by heat block and water bath on analytical sensitivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2). Also, we tested the effect of water bath heat inactivation method on the detection rate of SARS-CoV2 at 560C.
Results: all samples tested positive in heat block also tested positive in water bath. We observed similar viral detection rate of viral RNA at 560C for 15 min and 30 min, whereas inactivating samples at 560C for 45 min drastically reduces the virus detection by 20%.
Conclusions: water bath is not inferior to dry heat block, and we can use it instead of dry heat block in district laboratories. In lowering the limit of detection of the viral RNA, water bath is beneficial over heat block. However, inactivation of samples at 560C over 30 minutes drastically reduces the virus detection rate. Hence, samples shall not be heat treated prior to nucleic acid extraction.
Key words: SARS-CoV2, COVID-19, heat inactivation, heat block, water bath, N-gene, RdRP-gene