Respiratory
An 8 year old child is brought into the Emergency Department with a 1 week history of a violent paroxysmal cough. A classmate has recently been diagnosed with whooping cough. How should the diagnosis be confirmed in this patient?
Answer:
If the cough is of 2 weeks’ duration or less, culture of a nasopharyngeal aspirate or nasopharyngeal/pernasal swabs is recommended for people of all ages. However, a negative result does not exclude pertussis. Real-time PCR testing for the pertussis toxin S1 promoter region (ptxA-pr), and the insertion element IS481, of nasopharyngeal or throat swabs can also be used to confirm infection in people of all ages with symptoms of less than three weeks' duration.Pertussis
Respiratory
Last Updated: 12th February 2021
Whooping cough, also known as pertussis, is a highly infectious disease caused by the bacterium Bordetella pertussis, which produces pertussis toxin and other substances which are believed to have an important pathogenic role in the disease. Whooping cough is now relatively rare compared with the pre-vaccination era.
Clinical disease
The incubation period is about 7 - 10 days (range 5 - 21 days). Whooping cough is spread by aerosol droplets released during coughing and is considered to be infectious for from onset of symptoms until 48 hours of appropriate antibiotic treatment OR for 21 days from onset of symptoms if appropriate antibiotic therapy has not been completed.
- Catarrhal phase
- The catarrhal phase lasts between one and two weeks. Pertussis is rarely diagnosed during this stage unless there has been contact with a person who is known to be infected.
- Symptoms are often difficult to distinguish from those of other upper respiratory tract infections, and include: nasal discharge, conjunctivitis, malaise, sore throat, low-grade fever, dry, unproductive cough.
- Paroxysmal phase
- The paroxysmal phase typically occurs about 1 week after the catarrhal phase and lasts between one and six weeks. Between coughing fits (paroxysms), the person is usually relatively well, and has undisturbed sleep. The paroxysmal episodes during this phase:
- Typically consist of a short expiratory burst followed by an inspiratory gasp, causing the 'whoop' sound. The ‘whoop’ is less common in adults, and in children younger than 3 months of age (who may present with apnoea alone).
- May be severe enough to cause cyanosis in children, and are frequently associated with post-tussive vomiting. Adults may experience sweating attacks with facial flushing, and rarely, cough syncope.
- The paroxysmal phase typically occurs about 1 week after the catarrhal phase and lasts between one and six weeks. Between coughing fits (paroxysms), the person is usually relatively well, and has undisturbed sleep. The paroxysmal episodes during this phase:
- Convalescent phase
- A protracted cough can last for up to 3 months (convalescent phase), during which there is a gradual improvement in cough frequency and severity.
A previously infected person can become re-infected with pertussis, but subsequent infections are usually less severe. Vaccination does not always prevent infection, but it usually attenuates the disease.
Complications
Complications include:
- Secondary bacterial bronchopneumonia
- Secondary bacterial otitis media
- Apnoea following coughing spasms
- Seizures
- Encephalopathy
- Unilateral hearing loss
- Complications due to violent prolonged coughing
- Pneumothorax, abdominal/inguinal hernia formation, rectal prolapse, rib fracture, herniation of lumbar intervertebral discs, urinary incontinence, subconjunctival or scleral haemorrhage, facial/truncal petechiae, post-coughing vomiting leading to dehydration/malnutrition
Diagnosis
Whooping cough is a notifiable disease. If clinical features raise suspicion, investigations should be performed as per local health protection team advice and may include:
- If the cough is of 2 weeks’ duration or less, culture of a nasopharyngeal aspirate or nasopharyngeal/pernasal swabs is recommended for people of all ages. However, a negative result does not exclude pertussis.
- Real-time PCR testing for the pertussis toxin S1 promoter region (ptxA-pr), and the insertion element IS481, of nasopharyngeal or throat swabs can also be used to confirm infection in people of all ages with symptoms of less than three weeks' duration.
- If the cough is of more than 2 weeks’ duration, anti-pertussis toxin immunoglobulin G (IgG) serology may be employed in people aged over 17 years. Anti-pertussis toxin IgG detection in oral fluid can be used in children aged 5 to 16 years.
Treatment
Arrange admission if the person:
- Is 6 months of age or younger and acutely unwell.
- Has significant breathing difficulties (for example apnoea episodes, severe paroxysms, or cyanosis).
- Has a significant complication (for example seizures or pneumonia)
If admission is not needed, prescribe an antibiotic if the onset of cough is within the previous 21 days. A macrolide antibiotic is recommended first line: clarithromycin for infants < 1 month old, clarithromycin or azithromycin for children and adults and erythromycin for pregnant women. Co-trimoxazole is indicated if macrolides are contraindicated or not tolerated.
Otherwise, the mainstay of treatment is supportive and early treatment of secondary bacterial infections.
Prevention
Advise that children and healthcare workers who have suspected or confirmed whooping cough should stay off nursery, school, or work until 48 hours of appropriate antibiotic treatment has been completed, or 21 days after onset of symptoms if not treated. People who work in other settings should avoid contact with infants under one year of age who are unvaccinated or partially vaccinated until 48 hours of appropriate antibiotic treatment has been completed, or 21 days after onset of symptoms if not treated.
Offer antibiotic prophylaxis to close contacts of the ‘index case’ with suspected or confirmed pertussis (such as those living in the same household, or with overnight stays in the same room in an institutional setting), when the symptoms in the 'index case’ occurred within the previous 21 days, and the close contact is at increased risk of severe complications from pertussis (e.g. unvaccinated infants < 1 years) or when the close contact is at increased risk of transmitting infection to high-risk individuals (e.g. unvaccinated healthcare workers, pregnant women ≥ 32 weeks gestation).
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
