A nucleic acid test, often called a “NAT”, (or nucleic acid amplification test – “NAAT”) is a molecular technique used to detect a virus or a bacterium^[1]. These tests were developed to shorten the window period, a time between when a patient has been infected and when they show up as positive by antibody tests.

The term includes any test that directly detects the genetic material of the infecting organism or virus. There are multiple methods that fall in this group, including:

• Methods based on the Polymerase chain reaction. These tests use a primer to rapidly make copies of the genetic material.
  • A reverse transcriptase PCR (RT-PCR) is used for HIV and other RNA viruses.
  • Transcription mediated amplification uses a slightly different molecular method than PCR but has the same basic principle.
• Branched DNA (quantiplex bDNA) tests use a molecule that links to the specific genetic material.
• Ligase chain reaction

In 1999, new screening methods involving nucleic acid amplification and that protocol approved by FDA.

Nucleic acid Testing – Benefits:

• Detects low levels of viral RNA or DNA.
• Provides additional layer of safety to the blood supply because it allows the detection of infectious agents during their incubation period.
• Have the ability to detect viral mutants and occult infections.
• Highly sensitive and specific for viral nucleic acid.

Different Technology of Nucleic acid testing:

• Polymerase chain reaction (PCR)
• Branched DNA (bDNA)
• Transcription mediated amplification (TMA)
• Nucleic acid Sequence Based Amplification (NASBA)