At a glance

Also known as

Whooping cough tests

Why get tested?

To detect and diagnose a Bordetella pertussis infection

When to get tested?

When you have persistent, sharp spasms or fits of coughing (paroxysms) that the doctor suspects is due to pertussis (whooping cough); when you have symptoms of a cold and have been exposed to someone with pertussis

Sample required?

A nasopharyngeal (NP) swab or a nasal aspirate; occasionally, a blood sample drawn from a vein in your arm

Test preparation needed?

None

What is being tested?

This is a group of tests that are performed to detect and diagnose a Bordetella pertussis infection. B. pertussis is a bacterium that targets the lungs, typically causing a three-stage respiratory infection that is known as pertussis or whooping cough. It is highly contagious and causes a prolonged infection that is passed from person to person through respiratory droplets and close contact. Most cases of pertussis in Australia occur between August and February each year.

The incubation period for pertussis varies from a few days to up to three weeks. The first stage of the disease, called the catarrhal stage, usually lasts about two weeks and symptoms may resemble a mild cold. It is followed by the paroxysmal stage, which may last for one or two weeks or persist for a couple of months and is characterised by severe bouts of coughing. Eventually, the frequency of the coughing starts to decrease and the infected person enters the convalescent stage, with coughing decreasing over the next several weeks. Pertussis infection, however, can sometimes lead to complications such as pneumonia, encephalitis, and seizures, and it can be deadly. Infants tend to be the most severely affected and may require hospitalisation.

Pertussis infections used to be very common in Australia affecting a peak of 49,500 people in 1930 (800 cases per 100,000 population). Improved living conditions and the introduction of mass vaccination with the pertussis vaccine in 1953, had decreased this number to less than 5,000 in 2007 (3 cases per 100,000). However, neither the vaccine nor previous whooping cough infection confers lifetime immunity and  there are still periodic outbreaks of pertussis in young unvaccinated infants, in adolescents, and in adults. Improved diagnostic tests for pertussis have also contributed to the greater number of cases reported. In 2014, 11,866 cases of pertussis were notified nationally to public health units (70 cases per 100,000).

Pertussis testing is used to diagnose these infections and to help minimise their spread to others. Several different types of tests are available to detect pertussis infection. Some of these include:

Pertussis can be challenging to diagnose at times because the symptoms that present during the catarrhal stage are frequently indistinguishable from those of a common cold or of another respiratory illness such as bronchitis, influenza, and, in children, Respiratory Syncytial Virus (RSV). In the paroxysmal stage, many adults and vaccinated patients who have pertussis will present with only persistent coughing. Suspicion of pertussis infection is increased in patients who have the classic “whoop,” in people who have cold symptoms and have been in close contact with someone who has been diagnosed with pertussis, and when there is a known pertussis outbreak in the community. A pertussis PCR test will usually be ordered on these patients but should not be performed on close contacts that do not have symptoms.

How is the sample collected for testing?

Sample collection technique is critical in pertussis testing. For testing by PCR and culture, a nasopharyngeal (NP) swab or nasal aspirate is used. The nasopharyngeal swab is collected by having you tip your head back and then a swab is gently inserted into one of your nostrils until resistance is met. It is left in place for several seconds, then rotated several times to collect cells, and withdrawn. This is not painful, but it may tickle a bit, cause your eyes to tear, and provoke a coughing paroxysm. For a nasal aspirate, a syringe is used to push a small amount of sterile saline into your nose, and then gentle suction is applied to collect the resulting fluid. For antibody testing, a blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

Pertussis tests are used to detect and diagnose a Bordetella pertussis infection. Early diagnosis and treatment is critical to help limit spread of the disease.

There are several tests that may be used when a pertussis infection is suspected:

  • Culture – patient sample is placed into specialised and enriched nutrient media to grow and identify B. pertussis; results are available in 1-2 weeks. This test has been the "gold standard" for identifying pertussis and is used to diagnose a pertussis infection, although because the bacteria is fragile and can easily die during the specimen transport process, false negative results can occur when samples are collected in patients in the community setting.
  • Polymerase Chain Reaction (PCR) – this test amplifies the genetic material of the bacteria in a sample. Results are available within a couple of days.
  • Serology (antibodies), IgA, IgG, IgM – these blood tests measure the body's immune response to a pertussis infection or vaccination.

Direct Fluorescent Antibody (DFA) is an older technique that is no longer used in routine diagnosis of pertussis as it is less specific and less sensitive than pertussis culture and PCR.

Typically a pertussis culture and PCR test will both be ordered, as early in the illness as possible. Cultures are less likely to grow the organism 2-3 weeks into the illness, and cultures will be affected by some antimicrobial agents if the patient has been treated.

Serology is commonly used by medical practitioners in Australia but may be tricky to interpret. PCR and/or culture is preferred in the early stages of pertussis infection; serology on the other hand is best used in situations where a person has not sought treatment until late in their illness, or in an adult who has had a cough for an extended period of time. At present there is still significant variation in the types of serology tests used for the diagnosis of pertussis, therefore for an accurate interpretation of the serology results, your doctor may need to find out from the laboratory the type of antigen used in the serology test and liaise with a microbiology specialist.

Pertussis IgG antibodies will be present in anyone who has been vaccinated. Pertussis IgM and IgA antibodies will usually only be present a short time after vaccination or infection. These tests may sometimes be ordered to help evaluate and study the spread of pertussis in the community. Rarely, an antibody test may be performed to evaluate the adequacy of a person’s immune response to a pertussis vaccine.

When is it requested?

Pertussis tests are ordered when your doctor suspects that you have a Bordetella pertussis infection. A pertussis PCR and/or culture are typically performed when you have symptoms suggestive of pertussis, and as early in the illness as possible.

PCR testing should not be used to diagnose outbreaks of the disease. False positive results may occur when PCR is used to screen people who may have been exposed but have no symptoms of disease.

Symptoms during the first stage of the infection, called the catarrhal stage, may include typical cold symptoms such as a runny nose, sneezing, mild cough and/or a low-grade fever. After about two weeks, the paroxysmal stage begins and may include symptoms such as:

  • Frequent severe bouts of coughing sometimes followed by vomiting
  • Several rapid coughs followed by a whooping sound as the person inhales; affected adults may cough but not whoop, and infants may have trouble breathing and may choke more than whoop

These symptoms may last for one or two weeks or persist for a couple of months. During the convalescent stage, the severity of symptoms lessens, with the frequency of coughing gradually decreasing over the next several weeks.

What does the test result mean?

A positive culture is diagnostic for a B. pertussis infection, but a negative culture does not rule it out. Culture results are dependent on proper specimen collection and transport, duration of symptoms when the sample is collected, and prior antimicrobial therapy administered before the culture is taken.

A positive PCR test means that it is likely that the patient has pertussis. However, the PCR test may also be positive with other members of the Bordetella family. A negative PCR test means that it is less likely that the person has pertussis but does not rule it out. If there are an insufficient number of organisms in the sample, then they may not be detected. Both culture and PCR tests are less likely to be positive as the illness progresses.

The direct fluorescent antibody test is not as sensitive or specific as other methods. If it is positive, then the person may have pertussis, but this should be confirmed with a culture. A negative direct fluorescent antibody test does not rule out pertussis.

The presence of IgG B. pertussis antibodies may be seen with a recent infection but also after vaccination. A rise in the quantity of IgG B. pertussis antibodies between the acute and convalescent samples and the presence of IgM and IgA antibodies are evidence of a recent pertussis infection.

Is there anything else I should know?

The pertussis vaccination is given to infants as a series of injections. Those children who have not completed the series of pertussis vaccinations are at a higher risk of becoming infected. Even some people who have been vaccinated may be infected by Bordetella pertussis, but they will tend to have a less severe illness. Currently in some states of Australia a free pertussis vaccine is offered to parents and carers of young children.

International travellers should be aware that many less developed countries do not have widespread vaccination for pertussis. Infants who have not completed their series of vaccinations and people who have not had a booster vaccination in many years may be at an increased risk of contracting pertussis.

Common Questions

Can a throat culture be used instead of a nasopharyngeal sample from my nose?

A throat culture is not generally acceptable. During a pertussis infection, the organism is found in the tissues in the back of the nose, not in the throat or the front portion of the nose.

Can pertussis testing be done in my doctor's office?

No. There is no simple, rapid diagnostic test for pertussis. It requires specialised equipment and is typically performed in laboratories. Not every laboratory performs this testing – samples may need to be sent to a public health laboratory.

Why did my doctor report my child's pertussis infection?

Doctors are required to report pertussis to state health departments. Outbreaks are tracked and interventions, such as vaccination and appropriate antimicrobial therapy, are used to stop the outbreak.

Why do I hear so little about pertussis?

The number of people affected has dropped since widespread vaccination was instituted in Australia. Infants are routinely vaccinated, reducing the population who are susceptible. Pertussis outbreaks are sporadic instead of seasonal like influenza and RSV and may be under-reported and under-diagnosed, especially in adults who may not seek treatment when they have cold symptoms or a persistent cough.

My doctor said I have Bordetella parapertussis. Is this the same as whooping cough?

B. parapertussis is a bacterium that can infect humans in the same manner as B. pertussis, but the infection usually causes a milder respiratory illness. Culture methods and PCR tests can detect and distinguish B. parapertussis from B. pertussis, and both agents are commonly tested for since the clinical presentation may be similar in patients with either infection. There is no vaccine to prevent B. parapertussis infections.


Last Review Date: November 2, 2015