NEW DELHI: A day after advising states not to use the newly distributed rapid testing kits to detect coronavirus infection for the next two days, the ICMR issued a protocol reiterating their usage for surveillance purpose while stating that RT-PCR tests must be continued vigorously as the principal diagnostic test for Covid-19.In view of the issues raised by a few states about the rapid test kits, Additional Director General of Indian Council of Medical research (ICMR), Dr GS Toteja in his letter to Chief Secretaries of states and UTs on Wednesday said ICMR has always emphasised that RT-PCR test of throat and/or nasal swab is the confirmatory test for detection of COVID-19 at an early stage.It said that in its advisory dated April 17, the apex medical research body had clearly laid down the scope, purpose and usage of the rapid antibody tests."I would like to reiterate that antibody rapid tests are largely to be used as a tool for surveillance with respect to formation of antibody in persons exposed to the virus," Toteja said.He further said that globally also, the utility of this test is evolving and it is currently being used for detection of antibodies in individuals."These test results are also dependent on field conditions. We have been given to understand that many states have procured such kits and on state request, ICMR has also arranged and made available rapid antibody test kits with a clear understanding that these kits cannot replace the RT-PCR test diagnosis for Covid-19 cases," he said in his letter."However, to further assist the state, ICMR will continue to collect data from various states to assess the scope and extent of utility of these rapid antibody tests in field conditions of our country and will keep advising the states on regular basis," the letter added.He advised the states to follow the prescribed protocol for these tests and use it for the purpose for which these kits are meant."It is reiterated that to contain coronavirus infection, RT-PCR tests must be continued vigorously as the principal diagnostic tests," Toteja stated.At a press briefing held on Tuesday, Head of Epidemiology and Communicable Diseases at the ICMR, Dr Raman R Gangakhedkar, advised states to stop using the rapid antibody test kits procured from China for the next two days till it examines their quality in the wake of complaints that they are not fully effective.He also said the companies which supplied the kits will be asked to replace them if the kits are found to be faulty."High variations ranging from 6 to 71 per cent have been reported between the results of the rapid tests and RT-PCR tests. We will advise states not to use these testing kits for the next two days," he had said.These kits will be tested and validated in the field by teams from our eight institutes after which we will issue a clear-cut advisory for the states, Gangakhedkar had said.Last week, India procured five lakh rapid antibody test kits from two Chinese firms and they were distributed to several states reporting rising cases of coronavirus infection. The Rajasthan government on Tuesday said the kits were giving out inaccurate results.At present, the government uses the polymerase chain reaction (PCR) tests to detect coronavirus from throat or nasal swab samples of people. These take around five to six hours to show the results. In the rapid antibody tests, the blood samples of suspected patients are taken, and it normally takes around 15-30 minutes to give the result.The government has recommended the use of rapid antibody tests in hotspot areas.According to the ICMR protocol, officials said only those showing symptoms of influenza-like illness such as fever, cough and cold for seven days or more in hotspot areas should be made to undergo a rapid antibody test.Those who will be found positive must be quarantined at least for seven days and contract tracing should be initiated. Those who test negative should also remain under home quarantine for at least seven days."The RT-PCR test should be performed to confirm diagnosis of COVID-19 if clinical suspicion is high," an official had said.The death toll due to COVID-19 rose to 652 and the number of cases climbed to 20,471 in the country on Wednesday, registering an increase of 49 deaths and 1,486 cases since Tuesday evening, according to the Union health ministry.