Another major controversy has erupted after the Indian Council of Medical Research (ICMR) on Tuesday asked states to halt the use of rapid testing kits for COVID-19 for at least two days as the kits are giving inaccurate results.
The doubling rate of COVID-19 may be decreased in India, still, the cases of novel coronavirus are rapidly increasing in the country. India recorded less than 1,000 new daily cases only on two out of the last seven days (April 15-21).
With India in its second phase of lockdown, a major obstruction has come into India's road to increase testing with the new rapid test kits hitting a quality firewall. As per reports, rapid test kits that arrived 10 days later than originally scheduled are not giving as accurate results as expected.
Rajasthan reported problems following which the Indian Council for Medical Research (ICMR) on Tuesday asked states not to use these rapid test kits for the next two days. The batch of rapid test kits, imported from China, may be returned. This will delay the fight-back against the novel coronavirus outbreak in India.
Rapid test kits were pitched as a pivot to take the counter-coronavirus efforts to the next stage of mass-scale testing to get a better picture of the extent of COVID-19 spread in India. The government originally planned to increase testing volume to over 1 lakh a day from the current level of around 25,000.
Other Options For India:
The other test, called RT-PCR, is time-taking even though it returns more accurate results. RT-PCR stands for a reverse-transcription polymerase chain reaction. It is a method that is more favored and recommended by the World Health Organisation (WHO).
RT-PCR is used to detect the presence of a pathogen's specific genetic material. In this case, the pathogen is novel coronavirus or SARS-CoV-2. The test goes by another name, Nucleic Acid Amplification Tests (NAAT).
In the NAAT or RT-PCR test, the samples are collected from the upper respiratory tract. The sample is either a nasopharyngeal swab or a swab that has been gathered from the throat, behind the nose. It contains a mixture of mucous, saliva and some cells. This sample could contain viral RNA, that is, novel coronavirus if the person is infected with the virus.
The sample is sent to a designated lab, where specimen RNA is sifted from the rest of the materials. This RNA is transcribed (converted) into DNA using an enzyme by lab technicians. Then, this DNA is put in the RT-PCR machine that heats and cools the sample - a process that leads to Xeroxing of thousands of copies of the DNA. Then chemical markers are placed in the sample; if fluorescent flashes are seen in the machine, it signals novel coronavirus infection.
It is a lengthy and complex process. And, in the fight against novel coronavirus pandemic, time is armour. This is where the rapid test kits come in.
Rapid test kits take blood samples and uses serum -- blood fluid different from other materials such as RBCs -- to estimate the presence of novel coronavirus. Blood serum contains antibodies. Antibodies are also proteins just like novel coronaviruses. They are produced by immunity cells -- primarily the white blood cells -- to as weapons to fight pathogens, which are foreign bodies and called antigens.
The WHO says there are two types of rapid test kits to detect novel coronavirus infections. One is based on antigen detection and the other antibody detection.
The antigen-based rapid diagnostic test detects the presence of viral proteins (antigens) expressed by the Covid-19 virus in a sample from the respiratory tract of a person. But there is a limitation.
"With the limited data now available, WHO does not currently recommend the use of antigen-detecting rapid diagnostic tests for patient care, although research into their performance and potential diagnostic utility is highly encouraged," reads the world health agency's advisory.
The reason for this WHO caution is that "the sensitivity of these tests might be expected to vary from 34 percent to 80 percent".
For the antibody-based rapid diagnostic tests, the WHO says the majority of patients develop antibody response only in the second week after onset of symptoms. This means that a diagnosis of COVID-19 infection based on antibody response will often only be possible in the recovery phase.
This translates into an effective loss of opportunities for clinical intervention or interruption of disease transmission. The rapid test can, however, be used at a later stage to gauge herd immunity -- how many in a given population have antibodies -- to novel coronavirus infection.
This also means that a sufficiently large number of pre-symptomatic or asymptomatic patients of Covid-19 may not actually be detected by rapid testing kits. Symptoms take up to 10 days to show in a coronavirus infected person.
There is another caution that the WHO serves for antibody-based rapid test kits -- the one India has imported from China and now placed a two-day bar on its use.
The WHO says antibody detection tests targeting Covid-19 may also cross-react with other pathogens, including other human coronaviruses and give false-positive results.