Evaluation of nucleic acid testing [NAT] of blood donors

Context: Human immunodeficiency virus (HIV), hepatitis C virus (HCV), and hepatitis B virus (HBV) are easily transmitted through infected blood, to prevent this serological screening of blood units is a routine norm. Many cases could be missed if the testing is done in window period. To overcome this and to provide an additional protection many tests with better sensitivity and specificity like Nucleic acid testing (NAT) have been tried. Aims: To observe NAT reactivity trend for transfusion transmittable diseases, and to correlate ELISA and NAT methods in detecting HIV, HBV and HCV. Materials and Methods: A six years retrospective observational study conducted in Blood bank, Department of Pathology. ELISA and ID-NAT results of the donor samples for HIV, HBV and HCV were collected in a specially designed proforma and analyzed. Statistical Analysis used: Data entered in Microsoft excel sheets, means and percentages were calculated. Results: In 6years 52,417 units of blood collected, 44,600(85.08%) were voluntary donors and 7,817(14.92%) replacement donors. There were 521(0.99%) cases of HBV, 98 (0.19%) HIV and 48 (0.09%) HCV and two cases of HIV-HBV co-infection. About 557 were positive by both ELISA and NAT method (1.06%). Fifty eight cases were positive only by ID-NAT method and negative on serological testing accounting to the NAT yield of 1 in 893 cases. There were 2 cases of HIV-2 which were missed by NAT and picked up in ELISA. Conclusions: Screening of blood and blood products using dual testing with high sensitivity serological assays and NAT helps to detect potentially infectious diseases in all phases of infection.