Why serological test survey is being conducted in Delhi

Serological tests are basically blood tests which are used to determine whether a person was infected by Coronavirus (Covid-19) by examining the anti-bodies in their bloodstream. These tests are being conducted in Delhi on war footing to found out the extent of asymptomatic Covid-19 patients in the capital and how many of them were infected from Covid-19 and were cured without even realising. The survey will have a sample size of 2000 with people from ages being included.