The purpose of any blood/ blood product, when needs to be transfused to any patient, must be a safe one. For that reason, mandatory screening for diseases like HIV, HBV, HCV, Malaria & syphilis are done in all the authentic blood banks in Odisha. Conventionally screening tests for these diseases are usually done by rapid tests/ ELISA tests. During last few years to lessen the window period of these diseases, more advanced test modality like NAT (Nucleic Acid Testing) has been introduced in some transfusion centers in India. The present study has been done to find out the benefit & limitation of the NAT test over ELISA test. The study has been carried out over a period of two years in VIMSAR, NAT center of Odisha where all ELISA negative samples are subjected for testing. Some seronegative cases in ELISA when subjected to NAT testing showed positive results. The percentage of positive samples in NAT which have showed negative in ELISA test was found out to be 0.08% in HI, 0.27% in HBV &0.01% in HCV. NAT Screening may be beneficial in the population where sero-prevalence of Transfusion transmitted infection is high. Although NAT has got an added advantage of reducing the window period, all the blood centers of India cannot afford for the cost of NAT test, so proper donor deferral should be adopted during selection of eligible donors.