Types of Nucleic Acid Testing for HIV

STD/STI Tests at Clinics in London & UK »

Nucleic acid testing, often abbreviated to NAT, for HIV is a growing technology increasing in popularity thanks to its reliability and accuracy. NAT is actually an umbrella term which refers to a number of different technologies, all of which operate on the same basic principle but differ in terms of the specifics and how they go about detecting the virus. In this article we look at a couple of the main NAT techniques and how they are used.

What do all NATs have in common?

All NATs take the same basic approach towards the detection of HIV. The technique relies on detecting the genetic material specific to the virus, an approach which makes nucleic acid testing extremely accurate and reliable.

All living things possess a unique genetic code made up of sequences of nucleic acids, and by looking for particular sequences NAT techniques can allow for a reliable diagnosis of HIV.

PCR nucleic acid testing

PCR testing is a fairly widespread method of NAT which can reliably detect HIV within as little as 17 days of infection. PCR stands for Polymerase Chain Reaction, and you may hear this technique referred to as RT-PCR, or reverse transcriptase polymerase chain reaction. These are fancy titles for a technique which is in principle quite simple.

PCR is an effective method of detecting small amounts of viral RNA (genetic material). This is because the technique starts off by amplifying any viral nucleic acid sequences present in a sample, and in doing so any HIV can be accurately detected.

All PCR needs is a sample of plasma, which is basically the liquid component of human blood. Plasma is easily obtained from whole blood by a process called centrifugation, which involves spinning a sample at high speed until it separates into its constituent components. This can actually make the procedure more accurate as a lot of the material in whole blood can potentially interfere with the PCR test.

PCR isn’t only used for HIV testing, it is in fact a widely used and extremely powerful tool in a number of different sciences. This is one of the reasons why this particular technology is constantly improving in terms of its cost and effectiveness. The hope is that in time PCR tests will be simplified into a simple desk top kit which generates results quickly and is easy to use.

Branched DNA or Quantiplex bDNA Nucleic Acid Test for HIV

The Quantiplex approach takes a slightly different approach, although as mentioned previously, in principle the test works in the same way as PCR, through the detection of nucleic acid sequences. While PCR involves a series of cyclic reactions which increase the amount of viral RNA present in a sample, the Quantiplex approach concentrates any existing RNA for analysis.

Using a process similar to the one used to generate plasma (centrifugation), a sample is spun until all the virus present is concentrated. This condensed viral sample is then treated in such a way that HIV opens and releases its genetic content (viral RNA). This procedure is performed in a specially designed vessel lined with molecules to which, in short, RNA binds to causing a color change that indicates both the presence of RNA and the quantities in which it is made.

The Quantiplex Method offers its own distinct advantages, not the least of which is that the results of the test are an easy to interpret color change that would be relatively easy to translate into a simple home kit in the future. At present however, PCR remains the more popular method of NAT, and overtime these technologies will undoubtedly be vastly improved.

« How are Nucleic Acid Tests for HIV Performed? Why is Nucleic Acid Testing More Accurate than Antibody Testing? »

STD's & STI's