Nucleic acid testing (NAT) detects the viral nucleic acid present in the blood and differs from immunoassays as it detects the genetic material of the pathogens, not antigens or antibodies. An insight by Sumit Bagaria, MD, Hemogenomics
Blood transfusion is a lifesaving procedure and is considered the lifeline of critical surgical processes. But blood can also be an easy route for microbes to enter a patient’s body and result in deadly infections. It is the utmost responsibility of blood bankers or transfusion medicine practitioners that their patients do not acquire life-threatening infections from blood. To make sure that patients receive safe blood, which is free from any microbial
infection, blood screening has been mandated the world over.
In India, every unit of blood donated is strictly screened for HIV, HBV, HCV, syphilis and malaria. Blood screening is a critical process which is taken very seriously in every blood bank to avoid transfusion-transmitted infections (TTI). Though every blood donor undergoes a strict questionnaire before blood donation and then the blood unit
undergoes mandatory screening, there still are chances that infections can escape detection and result in TTIs.
Asymptomatic donors that are infected but do not show any sign of infection pose a major threat to the blood supply.
Such donors’ infected blood units should be caught beforehand during screening but sometimes they escape detection. The reason is Window Period donations. What is the window period? A window period of a screening or a diagnostic assay is defined as the time between infection and the time required for the assay to reliably detect the infection. The window period for serology-based assays is usually 15 days, 60 days and 35-40 days for HIV, HCV and HBV respectively. An asymptomatic donor when donating blood during the above-mentioned window periods, clearly escapes detection and the blood unit when transfused to a patient, results in a life-
threatening infection. Time and againthe indirect technique of immunoassay to catch window period infections is proven to be inefficient and incapable of detecting window period infections.
In the early 90s, the need for better and more reliable techniques and tests was realised post many TTI cases, which led to the adoption of Nucleic Acid Testing (NAT).
How does ID-NAT help over serology method of detection in blood screening?
A nucleic acid testing (NAT), also called nucleic acid amplification testing (NAAT) is a molecular technique that detects the viral nucleic acid present in the blood. NAT differs from immunoassays as it detects the genetic material of the pathogens, not antigens or antibodies. As NAT is a direct test and does not wait for the body’s immune response, it offers a much shorter window period. NAT is implemented in different formats in different countries. Among them, US-FDA approved Transcription Mediated Amplification (TMA) based Individual Donor Nucleic Acid Testing (ID-NAT) is the most sensitive NAT available. ID- NAT tests individual blood samples and
amplifies viral nucleic acid into billions of RNA amplicons as end products. TMA takes place in isothermal conditions and takes less time to produce billions of RNA amplicons. The fragility of RNA amplicons is an advantage as it is degraded easily post-reaction and there is next to zero chance of lab contamination. So, with higher sensitivity, shorter window period and low false reactive results, ID-NAT is the ideal blood screening assay.
What is the Procleix Panther system?
How is it proved to be super sensitive and specific? The PROCLEIX PANTHER System is a highly evolved, fully integrated, and automated NAT system for blood and plasma screening. The PANTHER System’s design can enable laboratoriesto improve workflow and operating efficiency, saving the operatortime and steps while offering rapid turnaround time to speed the release of blood to healthcare providers. The assay combines four tests in a single tube for the detection of HIV-1, HIV- 2, HCV, and HBV in donated blood and blood products. It saves operator time and steps, maximises walk-away time, reduces the risk of system error, features built-in process controls for the sample and results in integrity.
The Procleix Ultrio Elite Assay on Panther System has excellent sensitivity and specificity. It detects four deadly viruses which are HIV-1, HIV-2, HBV, and HCV. It reduces the risk of Transfusion Transmitted Infections (TTIs) and shortens window periods. It has the highest analytical sensitivity. No need to dilute the sample which reduces contamination of the sample. And it can detect the virus in low viral load.