Medical professionals can usually collect samples very quickly. However, people may have to wait for the results. While rapid tests take only around 15 minutes, slower tests may require an 8-hour wait.
Influenza, or flu,
Flu tests are important as they speed up the treatment process and help stop the flu from spreading.
This article examines how long flu tests take, test types, accuracy, and more.
All flu tests involve taking a sample of bodily fluids to test in a lab. The sample collection should take less than a minute, but some procedures, such as those requiring a bronchoscope, can take up to several minutes.
Different flu tests use different sample collection methods,
- Nasopharyngeal (NP) swab: This technique uses a swab that goes through the nose and into the nasopharynx to collect mucus. The nasopharynx is the uppermost part of the throat, which makes contact with the nasal cavity.
- Nasal or throat swab: This collects mucus from the nasal cavity or throat.
- Bronchial wash: This technique uses a bronchoscope, a thin tube that can enter the respiratory system. Doctors will place a saline solution into the bronchoscope before washing the airways. They will then use the bronchoscope to collect the washed mucus.
- Nasopharyngeal (NP) wash: This is similar to a bronchial wash, but it does not use a bronchoscope and washes mucus from the nasopharynx.
- Sputum: This technique involves collecting a sample of spit.
- Nasal aspirate: This involves using a thin tube and suction device to suck mucus from the nasal cavity.
- Endotracheal aspirate: Like a nasal aspirate, except that the mucus is from the windpipe, or trachea.
The table below summarizes the test types, collection methods, and general waiting times for results.
| Test | Sample collection methods | Time to results |
|---|---|---|
| Rapid influenza diagnostic tests | NP swab, nasal swab, and throat swab | |
| Rapid molecular assay | NP swab and nasal swab | Between 15 and 30 minutes |
| Immunofluorescence | NP swab or wash, bronchial wash, and nasal or endotracheal aspirate | Between 1 and 4 hours |
| Reverse transcription polymerase chain reaction (RT-PCR) and other molecular assays | NP swab, throat swab, NP or bronchial wash, and nasal or endotracheal aspirate, sputum | Between 1 and 8 hours |
| Rapid cell culture | NP swab, throat swab, NP or bronchial wash, nasal or endotracheal aspirate, and sputum | Between 1 and 3 days |
| Viral tissue cell culture | NP swab, throat swab, NP or bronchial wash, nasal or endotracheal aspirate, and sputum | Between 3 and 10 days |
The Centers for Disease Control and Prevention (
- Molecular assays: These include rapid molecular assays, RT-PCRs, and other nucleic acid amplification tests. They detect RNA from the flu virus, a substance that only exists when the virus is replicating.
- Antigen detection tests: These include rapid influenza diagnostic tests and immunofluorescence assays. The tests look for flu antigens — proteins on the surface of flu viruses that the immune system “recognizes” as a threat.
- Viral cultures: These include rapid and viral tissue cell cultures. They involve providing the flu virus with an ideal environment to replicate. This allows public health officials to test them more thoroughly. However, viral cultures are not useful from a diagnostic perspective, as they take too long.
Research has shown that different flu tests vary in accuracy. The following table summarizes what scientists know about this, according to the CDC:
| Test | Accuracy |
|---|---|
| rapid influenza diagnostic tests | can detect between |
| rapid molecular assay | can detect between 90% and 95% of flu infections |
| immunofluorescence | can detect between |
| RT-PCR and other molecular assays | can detect up to |
A variety of locations can provide flu tests. These include doctor’s offices, hospitals, and some pharmacies.
An individual who thinks they may have the flu can discuss this with a doctor, who can recommend the best place for testing.
This section answers some frequently asked questions about flu tests.
How long does flu show up on PCR?
There is some variation in how long PCR tests take to detect flu. It all depends on the specifics of the sample and the test.
Generally speaking, such tests can take between
How accurate is the rapid flu test?
There are two main types of rapid flu tests: rapid influenza diagnostic tests and rapid molecular assays.
Rapid influenza diagnostic tests can detect between
To perform flu tests, doctors must collect a sample. The sample collection process should only take a few moments.
Rapid influenza diagnostic tests and rapid molecular assays only take between 15 and 30 minutes to provide results.
Immunofluorescence, RT-PCR, and other molecular assays take between 1 and 8 hours. Viral cultures, which are not useful for diagnostic purposes, can take several days.