About Polymerase Chain Reaction (PCR)
PCR is one of the techniques for the detection of nucleic acid (NAAT- Nucleic acid amplification test) which has become the gold standard for the diagnosis of many infections, especially in detecting viral pathogens.
In this era of the Covid 19 pandemic, it has become very essential to diagnose at the earliest for the purpose of treatment and for infection control. At present RT- PCR is considered as the gold standard for detection of SARS CoV2, depending on the assay the time taken for the results would range between 2-3 hrs. It requires a lot of equipment and sophistication to perform the test and is possible to perform in reference laboratories only.
Need for Rapid Point of care test (Rapid PCR)
Point of Care test (RT PCR Test) with lesser turnaround time is a need for clinical management. But there has been a drawback of false-negative results when the viral load in the sample is below the limit of detection of the assay, symptomatic negative cases must be confirmed by more sensitive methods. Many tests have been authorized by FDA for emergency use for COVID 19 as a Point of care test.
Rapid nucleic acid amplification/PCR test for SARS CoV 2
Here is one of the rapid nucleic acid amplification/PCR tests which are used as a point of care test for detecting SARS CoV 2, and the approximate TAT are discussed below:
Isothermal Nucleic Acid Amplification Test
- EX: Abbott ID NOW COVID 19 the time taken for the result from sample insertion is 13 min, targets RdRp gene of SARS CoV 2
- Cue COVID-19 Test the time taken for the result from sample insertion is 20 min targets N gene of SARS CoV 2
(Reverse Transcriptase loop-mediated isothermal amplification)- which will take 30-40 min for the result.
Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) technology
It is considered equivalent to RTPCR - TataMD CHECK CRISPR Test Turnaround time is ~45 min.
- Xpert Xpress SARS-CoV-2 test (Cephid)- cartridge-based PCR test and will take 50 min for the result targets N gene an E gene of SARS-CoV-2
- Truelab workstation includes sample preparation, an RNA extraction system, an RT-PCR machine, battery operated turnaround time is 45 min.
It has been possible to give the result at the earliest with the help of the Point-of-care test. Rapid PCR tests have proved to be a boon in general for reaching a low TAT point of care test in the case of Covid-19.