Friday, April 17, 2020

To Test of Not toTest



In a fish market you can hardly hear yourself speak. The Social Media and MSM have become not too different. We have many voices speaking at the same time, all at high decibels, it has become difficult to glean information from this media created tumult.
There are many people who are very vocal that ‘Testing’ is the solution and then go on to build a nebulous connect between ‘Testing’ and ‘Control over Covid-19 virus’ aka ‘Chinese Virus’. The need for testing has been repeated so many times by so many opinion makers that the public seems to have ceded that without ‘Testing’ we have no solution to defeat the virus.
Those who think slow will agree that ‘Testing’ has a purpose, as a bare minimum.
In India, I believe predominantly PCR Testing being is being conducted to detect presence of the virus in a population that came in contact with infected persons and to confirm the presence of symptom in persons showing symptoms.
From this group if few were infected and showed no to mild symptom, they probably got immunity and no test was done to confirm and no effort to collect the data.
What will PCR test reveal? If a person is infected or not.

The pro-more-test are asking for increasing the target population to entire population. From whatever little tests we have carried out on general population has shown about less than 5% have been affected. We know what to do with them.
What about the 95% of the tested but negative? The results help us with little value because we only know that these are not infected yet and may be infected in future.
While testing the people who had contact with infected person(s) this may be useful as the infection may be detected early and any treatment that may yield benefit may be begun early to reduce the risk of deterioration.
However, the antibody test may be conducted on a population not known to have come in contact with infected population to measure the spread of the infection in general population.
This testing can be at best be a ‘Sample’ testing. Appropriate decisions can be taken based on the outcome.
The Antibody test may reveal that a person has been infected. But it is not so simple. The symptoms in majority of cases appear along with the peak viral replication. AND, in earlier stage the risk of false negative for antibody test is high. The antibodies are made post infection and around the 5th day of the infection may become detectable, by which time most infected have begun to show symptoms. The effort to identify an infected person using antibody tests in early stages is too high in comparison to PCR test.
If an area shows more prevalence than the rest, this test helps to conduct PCR tests to identify the carriers and to isolate them early. Antibody tests are bellwether tests.
Summing up, PCR tests on everyone is not only expensive but also needs to be repeated till everyone is tested positive. Antibody test “alone is not recommended for COVID-19 diagnosis due to the kinetics of infection” Link here
Antibody testing of, say 500K tests a month spread over different places after the lockdown will be very useful to check if the infection has risen its head again; if any particular region is seeing more than the other.
However, what we fail to identify is, I assume in the absence of any positive communication from authorities, the number of recovered people. These are people who have lower chances of relapse, hence have low probability to carry to uninfected people. Kind of asset.
By not testing for antibody, we also miss out on the number of people who may have acquired immunity as many people show no to mild symptoms.
The cost of conducting one round of antibody testing may be around 6 lakh crores according some sources. Tests may have to be repeated on same population albeit on smaller and smaller numbers. This is not a feasible solution.
Conclusion is, PCR Testing for presence of Corona in target population that had contact with infected persons pays high dividend and is being done by the Govt of India
Antibody testing is being conducted as sample (there is no hurry to cover the entire country) and will identify high risk areas.
Now request those who are repeatedly asking for more testing, kindly be specific, what kind of testing are you pleading for? Unless that is made clear, do not expect any sensible response. May be few will join the mindless chorus of worthless effort. Nothing more.