Comparison of two RT PCR methods with two different genes for detection of severe acute respiratory syndrome coronavirus 2 (SARS-COV2)

ABSTRACT

Background-aim: World Health Organization (WHO) announced that diagnostic testing for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-COV2) should be performed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Most of these methods use different gene props and therefore the sensitivity and specificity of each method may different. In this study, we have compared two RT-PCR methods using two different genes for detection SARS-COV2. Methods: A total of random 40 nasopharyngeal swab samples were collected, transported and received in iced box shipment. All samples were performed on two separate semi-automated PCR systems (Qiagen and Abbott m2000). For Qiagen method, 200uL from each sample were added in 96-well QiAcube plate which loaded in QiAcube HT (SN019658;Qiagen, Germany) to extract RNA. Following extraction, master mix prepared using SARS-COV2-RT-PCR kit 1.0 (REF 821005;Altona, Germany) for 44 samples including 40 patient samples, two negative controls using nuclease-free water (with and without internal control), and two positive controls (with and without internal control). Extraction elute of each sample (20uL) added to master mix (10uL) to have a total volume of 30uL which uploaded into Rotor-Gene Q (SNR0219307;Qiagen, Germany). The primer pair used to amplify S gene and E gene in SARS-COV2. Amplifications were done as follow reverse transcriptase (20 minutes at 55oC);initial denaturation (2 minutes at 95oC);45 cycles of denaturation (15 seconds at 95oC), annealing for (45 seconds at 55oC), and extension (15 seconds at 72oC). Results reported as valid for internal control less than 35 cycle threshold (CT). The Abbott m2000 System uses SARS-CoV-2 assay was a dual target assay for the RdRp and N genes. All 40 samples were extracted using m2000sp (Abbott, United States) as recommend by manufacture using 100uL. An RNA sequence that was unrelated to the SARS-CoV-2 target sequence was introduced into each specimen at the beginning of sample preparation. This unrelated RNA sequence was simultaneously amplified by RT-PCR and serves as an internal control (IC) to demonstrate that the process has proceeded correctly for each sample. Following extraction, master mix (20uL) added to extraction elute of each sample (30uL) to have a total volume of 50uL which uploaded into m2000rp (Abbott, United States). Amplification were done as follow reverse transcriptase (25 minutes at 55oC);initial denaturation (5 minutes at 94oC);40 cycles of denaturation (20 seconds at 94oC), annealing for (55 seconds at 55oC), and extension (15 seconds at 72oC). Result: All samples had valid extraction process with a CT value of internal control between 26.97 to 28.89. A total of 30 samples displayed positive results and 10 samples exhibited negative results with 100% agreement for both methods. This has resulted with a 100% accuracy between both methods. Conclusions: Both semi-automated methods from Qiagen and Abbott are comparable and accurate despite different technology and different primer genes.