*ANTIGEN or RT-PCR test: whom to choose ?*
( _Some facts about *Ct cycle* 24 or 40_ )
..
OK, you have given your nasal swab for corona testing. Then what happens to the sample in the lab.
*RT-PCR*
When a sample enters the test, the machine is basically looking for virus RNA. So it goes on amplifying the extract till it detects the culprit virus RNA.
The *Ct* is the _number of cycles it takes to detect the virus._ Thus, if the Ct value is high, then it means that there is less virus in the sample. And if the machine detects the virus in fewer cycles, then the virus load is high.
( _PCR machine is a Bhasmasura._ If we run your sample through still more cycles, it will detect more dead and fragments of virus. More test positives will return.)
In India, *ICMR has set it at 40*. So, the test will go through 40 cycles before returning a negative report.
In India, your viral load is getting multiplied by maximum 40 to return a positive report. That is a bit high.
So we are detecting more asymptomatic, non infectious cases. We have more RED ZONES and more number of SHUT DOWN episodes as a consequence.
*WHAT IF WE had SET a CUTOFF of 24 ?*.
80-90% confirmed cases today would have escaped detection. It's OK as most of them would have been non infectious. Our Covid stock value would've dived south.
..
_What can happen to you in that scenario ?_
Your chances of testing negative will be high.
Though you would be missed when you have extremely low dose of virus load.
But if India will set the threshold to 50, still more number of people will be positive. More asymptomatic, non infectious cases will be unearthed. Our Covid statistics will peak north. ( More non viable and fragmented virus will be detected.)
_Is it for the BETTER or for the WORSE ?_
If you have one virus in your nose you're already infected. You may not pose any harm to yourself or your family.
But you will never know if your system would over react to that lone virus and unleash a cytokine storm. That way it can do more harm to your body than good.
( A *cytokine* is a _specially trained sharp shooter deployed to find and kill the Coronavirus._ There can be some collateral damage to our own body in the process.)
*Antigen Test*
A higher viral load is required for our antigen test to be positive. It's possible that you may still harbour the virus when antigen negative but you are surely non infectious.
The bigger outcome is we shall have less containment zones , fewer shutdowns. Our economy will be bled less.
But the antigen may miss that odd man who still harbors one or two live virus. How would his cytokines react to those viruses is unpredictable.
Anyway some of the viruses are always missed at Ct 40 also.
That is the reason we find some Covid lung on CT scanners even in patients who are PCR negative.
...
_The bottom line._
*Antigen test is good for our economy.*
*RT-PCR may be good for our health*.
( A bit technical.
But I've cut a lot off jargons to make it simple at the cost of medical facts.)
_Ramakanta Mahapatra_
ટિપ્પણીઓ નથી:
ટિપ્પણી પોસ્ટ કરો