How COVID-19 testing works

There are 2 main types of COVID-19 tests in New Zealand: a rapid antigen test (RAT), which detects protein from the virus, and a Polymerase Chain Reaction (PCR), which identifies genetic material from the virus.

Rapid antigen tests (RATs)

Rapid antigen tests detect specific proteins of the COVID-19 virus, such as the spike protein. They are less accurate than PCR tests for detecting COVID-19, especially when you have no symptoms or the amount of virus in your system is low. This is the viral load.

RATs tend to be more accurate when the viral load is high and you are infectious. The main advantages of rapid antigen tests are that you:

  • can do these yourself at home
  • will have results within 20 minutes.

How to use a RAT

Reverse transcription polymerase chain reaction (PCR) test

The most accurate test for detecting if you have the virus for COVID-19 is a PCR test. This test detects genetic material from the virus in the sample. For the COVID-19 virus this is RNA.

Laboratories can sequence the genetic material from a PCR test to identify which variant of COVID-19 a person has. Whole genome sequencing takes the genetic material detected from a PCR sample. It then generates a complete RNA sequence of the COVID-19 virus. This helps trace outbreaks and new variants.

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