Pertussis (whooping cough) closely resembles many other upper and lower respiratory tract infections and a proper diagnosis is essential in order to commence with the appropriate treatment as soon as possible. Many cases of pertussis are initially misdiagnosed for more common respiratory tract infections.
It is only upon the onset of the typical ‘whooping’ cough (stage 2) or continuation of symptoms beyond the expected timeline of other respiratory tract infections that pertussis may be considered as a differential diagnosis.
Testing for Whooping Cough (Pertussis)
Ideally laboratory tests should confirm the presence of the Bordetella pertussis bacterium. However, if the typical symptoms associated with pertussis, especially those of stage 2 which are characteristic of the disease, are present coupled with the knowledge of any outbreak, your doctor may commence treatment without further testing.
In order to test for pertussis, a nasopharyngeal swab or aspirate (suctioned nasal discharge) can be sent for a culture. Any microorganisms are grown on a nutrient medium and identified. Isolating the bacteria by this method is conclusive for diagnosing pertussis and the appropriate treatment can be commenced.
In addition, a bacterial culture will help to identify the strain of the bacteria. The sample (swab or aspirate) must be taken within the first weeks from the onset of symptoms. A culture may take one to two weeks before the test results are available.
A PCR (polymerase chain reaction) test is quicker than a bacterial culture. By extracting and amplifying the genetic material of any microorganisms in a sample (nasopharyngeal aspirate), the type of microorganism can be identified.
It is effective for aspirates that are taken within the first 2 weeks of the onset of whooping cough symptoms or up to 4 weeks for infants and unvaccinated individuals. Results are available within a few days.
Pertussis Blood Tests
Blood tests are considered as an additional diagnostic tool, especially 2 weeks or more after the onset of symptoms.
- A complete blood count (CBC) will monitor the levels of the different type of blood cells. High levels of lymphocytes (white blood cells) indicates the body’s response to an infection. It will not conclusively identify the type of microorganism.
- Antibody tests may also be done to assess your immune system’s response to a specific antigen, either the bacteria itself or its toxin.
Results may be available within a few hours to a day or two.
Pertussis Chest X-Ray
A chest x-ray cannot conclusively confirm a diagnosis of pertussis, however, it will indicate complications and other upper respiratory tract disease. Fluid in the lungs, inflammation or consolidation of the lung tissue may be indicative of pneumonia, a common complication of an untreated pertussis infection in young children and infants. Dilatation of the bronchial tree is known as bronchiectasis, which is another complication of pertussis that may be detected upon a chest x-ray.
Pertussis, whooping cough, is a bacterial infection of the respiratory tract that is very contagious, especially among infants. It is caused by the bacteria Bordetella pertussis and first targets the upper respiratory tract although it can quickly spread to the lower respiratory tract where it may result in a host of complications. Depending on the stage of the condition, age of the patient and signs of any complications, the therapeutic approach may differ.
Immunization is the most effective means to prevent whooping cough although it does not guarantee 100% protection. The vaccine is routinely administered to children along with diptheria and tetanus. A pertussis shot immediately after contracting the infection will not provide any therapeutic benefit.
Children older than 12 years and adults should consider pertussis vaccine shots in the event of an outbreak. For more information on a pertussis shot, refer to the article on Whooping Cough Vaccine.
Antibiotic treatment is most effective in the first stage of pertussis known as the catarrhal phase. Refer to Whooping Cough Stages for more information on the different phases.
Antibiotics in the second stage (paroxysmal phase) may not reduce the severity or duration of the typical cough (whooping) associated with pertussis. However, it may be necessary if the bacteria are still present, which can be confirmed with a sputum culture or if there is a risk of transmission to younger household contacts, especially infants younger than 6 months.
Cough mixtures and expectorants are of little benefit in pertussis.
The antibiotics above are known as macrolides. Erythromycin and clarithromycin are not suitable for infants younger than 1 month of age. In cases of macrolide-hypersensitivity (drug allergy), co-trimoxazole (trimethoprim-sulfamethoxazole) may be used.
Household contacts should be treated with erythromycin to prevent secondary transmission.
- Infants younger than 6 months of age are routinely hospitalized to prevent complications like pneumonia, bronchiectasis, seizures and brain damage.
- In older patients, hospitalization is necessary in severe cases. Children between 6 months and 18 months of age are also high risk groups and should be hospitalized immediately if the first sign of any complication is present.
- Depending on individual cases, hospitalization may be necessary for anywhere between 3 to 10 days.