What is Nucleic Acid Test (NAT)?

17 March, 2021

The plasma collected from plasma donors is rigorously tested for harmful viruses such as HIV, Hepatitis B, and C.  

The screening ensures that these infections are not transmitted to patients for whom the plasma is collected and made into life-saving therapies.  

Traditionally, collected plasma is screened with antibody tests, which are aimed at detecting antibodies that our immune system produces in response to an infection.  

But antibody tests pose a huge limitation. They have a wide 'window period' — the time between infection and detection of antibodies. Such a time constraint makes the manufacturing process longer and less efficient.  

A highly advanced, more effective, and efficient alternative is the Nucleic Acid Test (NAT).  

What is NAT?  

Instead of looking for antibodies, the Nucleic Acid Test (NAT) directly looks for genetic bits of viruses. In scientific jargon, NAT amplifies targeted regions of viral ribonucleic acid or deoxyribonucleic acid (DNA).  

NAT’s biggest advantage is its narrow window period since viral genetic material becomes detectable far sooner than antibodies. On average, HIV’s window period is found to be 2.93 days, while Hep B’s and Hep C’s are 10.34 days and 1.34 days, respectively. 

Though NAT is highly effective, it is used primarily by developed countries. This is because implementing NAT is expensive: it demands high technical expertise, and dedicated facilities, and different kinds of equipment. Still, many countries are gradually adopting NAT in tandem with antibody tests, striking a balance between time and money. 

Nucleic Acid Test (NAT): How? 

NAT can be implemented in two ways: 

Mini-pool Nucleic Acid Test (MP-NAT) 

Collected samples (usually, 16 or 8) of plasma are pooled and tested together.  

Though MP-NAT is more efficient and less expensive, it can instead be counter-productive when a test returns positive for an infection. Then, the entire pool requires resolution — additional steps taken to test, identify, and remove the infectious unit.  

Secondly, diluting the genetic bits of the virus is also known to decrease the sensitivity of the test. 

Individual Nucleic Acid Test (ID-NAT) 

The alternative is the Individual Nucleic Acid Test (ID-NAT). As the name suggests, collected samples are individually tested for infections.  

ID-NAT is hence more sensitive and time-efficient: the unit found infectious is removed while the rest of them are advanced. Though ID-NAT costs more than MP-NAT. 

That said, most facilities will use both tests together, as explained, to strike a balance between time and money.  

A small number of samples are pooled and tested (MP-NAT). If the test shows no trace of infections, the units are advanced for further testing and production. If the test detects one, the handful of units are tested individually (ID-NAT).  

The unit is identified and removed, and the donor is notified and counseled.  

Learn more about plasma at www.iplasma.life 

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