Laboratory and diagnostics · Treatment guide
PCR Testing
Sampling conditions for PCR testing, the effect of timing on the result, and interpretation of the result alongside clinical findings.
Updated: · General information
PCR Testing: what approach is taken?
PCR (polymerase chain reaction) is a molecular method that amplifies and directly detects a pathogen's genetic material. Unlike antibody tests, it does not indicate a past infection but the presence of the pathogen at the moment the sample was taken. Because how and when the sample is collected can affect the result, the decision to test and its timing are determined by clinical assessment. The result is interpreted together with symptoms and examination findings, never in isolation.
Areas of assessment and treatment
- Direct detection of the pathogen by molecular method
- Correct sampling technique and timing
- Interpretation of the result alongside clinical findings
Timing can change the result
PCR shows the pathogen present at the moment the sample was taken. In a sample collected too early, the pathogen may not yet have reached detectable levels; after symptoms have resolved, residual genetic material may still be detected for some time. The timing of the test is therefore set according to the onset of symptoms and any history of exposure.
It is not the same as an antibody test
PCR looks for the pathogen itself, whereas antibody tests measure the immune response. The two answer different questions and are not interchangeable. Which test is appropriate depends on what is being investigated and at what stage of the illness.
What is assessed at the first consultation?
Your medical history, your current symptoms, the medicines you take and your needs in daily life are all discussed. You may share any previous investigations you have. Suitable options are considered together after the physician’s assessment.
Your questions
Patient information
Does a negative result definitively rule out illness?
Not on its own. Sampling technique, timing and the site from which the sample was taken can all affect the result. If symptoms persist, your doctor may request a repeat test or a different investigation.
How long do results take?
This depends on the panel being run and the laboratory's schedule. You can obtain current information from our centre when booking your appointment.
