NEW DELHI: The much-awaited consignment of five lakh rapid antibody diagnostic kits from China has finally arrived in India but ICMR explained that these are to be used for surveillance and tracking infection trends for Covid-19 and are not meant for diagnosis.The kits will be used in hotspots as well as in coldspots- areas with no reported incidence or low prevalence of Covid-19- to ensure no significant cases are left out of surveillance, officials said.The serology or rapid antibody kits provided by two companies— Lieozon and Wanflo- are meant to detect antibodies developed by a human body to fight the infection and not the infection itself. Hence, this first generation test will be used for surveillance and not early diagnosis, said Dr R R Gangakhedkar, head of epidemiology and communicable diseases at the Indian Council of Medical Research (ICMR).“If virus enters my body, my body will prepare a weapon to fight this virus which are known as antibodies. Antibodies are exactly the opposite of the virus which is why it disables the virus. There are types of antibodies, the first of these is IGM which does not stay for more than a few days. Detection of IGM antibody means that the infection is recent. When IGG antibody appears, I will know that my immune system is improving. If I see only IGG antibody and no IGM antibody, I can assume that this is an old infection,” Dr Gangakhedkar said explaining the interpretation of the results that these kits provide.Over concerns about quality of rapid antibody tests that have arrived from China in view of the experience of other countries, Dr Gangakhedkar said the sensitivity and specificity of these tests are usually low and therefore, they are best used for research and surveillance instead of diagnosis of Covid-19.“If we conduct the antibody test after 10 days or two weeks, these antibodies will appear in only 80 per cent of the patients. This is why these tests are not used for diagnosis but for surveillance,” he said.Explaining how it is useful for research, he said, “While monitoring the trend, even if there is a slight error in specificity, it will be uniform across the sample size and therefore it will not impact our observation of the overall trend,” he said.So far, over 2,90,401 samples have been tested and of these 30,043 on Wednesday itself. ICMR said at present there is a capacity to test 42,418 samples and if the labs start working in two shifts they can test around 78,000 every day.Dr Gangakhedkar also said there are adequate stocks of testing kits for eight weeks.