Testing for SARS-CoV-2
Preparing samples for outpatient RT-PCR diagnostics
Diagnostic testing for suspected SARS-CoV-2 is in full swing. According to Christian Drosten*, virologist at the Charité Hospital in Berlin, the moderate course of the epidemic in Germany to date is all thanks to this laboratory testing. Many laboratories therefore now need reliable devices for safe sample preparation, especially in the run-up to RT-PCR testing.
Three phases of sample preparation for the RT-PCR test for 2019-nCoV
The WHO has issued guidelines for the laboratories that are conducting tests. Safe test results for 2019-nCoV after a nasal or oropharyngeal swab require thorough sample cleaning beforehand.
With IKA laboratory equipment for the life sciences sector, the individual steps of preparing samples can be carried out reliably and quickly. Above all, IKA devices can be operated by everyone - including employees who may need to be trained and familiarized quickly in medical diagnostic lab testing as a result of the current situation. Before the actual test for SARS-CoV-2 can be carried out, three phases of sample preparation are required first.
When samples are prepared, cells from the oral mucosa are centrifuged, isolated and mixed to create cell suspensions. Here, as is the case in all of molecular biology, pipettes with RNAse/ DNAse-free filters are required, since RNA is destroyed very quickly by enzymes, such as RNAse. The filter also effectively prevents cross-contamination. Depending on the sample type, larger pipettes than those recommended by the WHO can also be used. The new PETTE series from IKA offers the added benefit of ergonomic design. Frequent pipetting in everyday testing is therefore a breeze. In addition, centrifuges and shakers are also used.
The envelopes of the viruses are then broken open. Here too, safe pipetting is the be-all and end-all. For temperature control, high-quality thermal shakers with 1.5 ml attachments or 2 ml attachments, such as the IKA MATRIX Orbital Delta F1.5 or F2.0 , are recommended.
Purification and extraction
For purification and extraction, fixed or, ideally, variable pipettes are required, since different sizes are recommended by the WHO (2, 10, 200 and 1000 µl). The broken up material is then centrifuged again. The IKA G-L midi centrifuge, for example, is suitable for the washing and separating processes in this phase.
The actual test can only be carried out after these three preparatory phases. For the test, the RNA of the coronavirus that may be present must first be rewritten to cDNA and reproduced in a thermal cycler to a detectable number of 10^9. Reproduction takes place with the help of so-called “primers” (DNA fragments that correspond to the RNA of the virus), which, if RNA or cDNA of the coronavirus is present, initiate the reproduction process. The primers of laboratory-made coronavirus genetic material are added to the sample to find out whether the coronavirus genetic material can attach to the patient sample (= positive) or not (= negative).
Testing for SARS-CoV-2
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