Why is Nucleic Acid Testing More Accurate than Antibody Testing?

As technologies evolve, questions are often raised about how newer methods compare to tried and tested techniques. This is most definitely the case in the field of HIV testing, where the staple method of detecting the virus has been antibody testing for many years. More recently however, the advent of nucleic acid based testing has raised questions about whether or not antibody tests should still be used when testing for this life changing condition.

How are nucleic acid tests different to antibody tests?

Antibody testing has been a reliable method of detecting a host of different conditions for many years. This approach detects viruses and bacteria by looking for elements of your body’s natural defensive response against any invading agents. These elements are referred to as antibodies, and are generated as highly specific agents working against particular viruses and bacteria, and this specificity is what makes them such useful markers in testing.

By detecting antibodies to HIV, antibody tests like the ELISA assay can reveal whether or not a person has been infected with HIV.

Nucleic acid testing methods (NATs) take a different approach to the detection of the virus. NATs essentially look for HIV’s genetic material, which is ultimately a coded sequence of nucleic acids. This sequence is highly specific to the virus, and by looking for it NATs can accurately report whether HIV is present or not.

Why are nucleic acid tests more accurate than antibody tests?

Accuracy is an extremely important consideration when it comes to any kind of medical testing. Unfortunately all testing methods are limited by something called the window period, which is a length of time after infection during which a test has a higher chance of incorrectly reporting an absence of disease (false negative).

The window period varies immensely, and is hugely dependent on both an individual’s response to a pathogen and the testing technique used. Antibody techniques require a certain amount of antibody to be present before they can report reliable results, which is why the window period for antibody tests can be quite long and quite variable. The window period for antibody tests can range from between 3 weeks to 6 months, and this is quite a long period of time for someone who is concerned about HIV.

Nucleic acid tests typically have shorter window periods, and this means that they can be used more reliably, particularly in cases where the exact point of infection isn’t entirely clear. A commonly used method of NAT called PCR has a window period of about 17 days, much shorter than the several weeks minimum antibody tests often involve.

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