From the Guidelines
Diagnosing croup and pertussis requires a comprehensive assessment of clinical symptoms and confirmatory testing, with pertussis diagnosis primarily based on clinical judgment and laboratory confirmation through methods like PCR or culture of Bordetella pertussis, as recommended by the most recent guideline 1.
Diagnostic Criteria for Croup
- Croup diagnosis is primarily clinical, based on the characteristic "barking" cough, inspiratory stridor, hoarseness, and respiratory distress that typically worsens at night.
- A lateral neck X-ray may show the classic "steeple sign" indicating subglottic narrowing.
- Croup most commonly affects children aged 6 months to 3 years and is usually preceded by upper respiratory symptoms.
Diagnostic Criteria for Pertussis
- Pertussis diagnosis involves recognizing the distinctive paroxysmal coughing fits followed by the characteristic high-pitched "whoop" sound during inspiration, particularly in children.
- Early symptoms resemble a common cold with runny nose and mild cough.
- Laboratory confirmation is essential through nasopharyngeal swab for PCR testing or culture of Bordetella pertussis, with the most recent study 1 emphasizing the importance of clinical judgment in diagnosis.
- Blood tests showing elevated white blood cell count with lymphocytosis can support the diagnosis.
- Pertussis should be suspected in patients with prolonged cough (>2 weeks), especially if unvaccinated or with incomplete vaccination, as suggested by earlier guidelines 1.
- Early diagnosis of both conditions is crucial for appropriate management and preventing complications such as respiratory failure in severe cases.
- The decision to treat with antibiotics is frequently based on a clinical diagnosis rather than waiting for laboratory confirmation, highlighting the need for prompt action in suspected cases of pertussis 1.
From the Research
Diagnostic Criteria for Croup
- Croup is characterized by upper airway obstruction resulting from swelling of the larynx, trachea, and bronchi, leading to inspiratory stridor and a barking cough 2, 3
- Many patients experience low-grade fevers, but fever is not necessary for diagnosis 2
- Laboratory studies are seldom needed for diagnosis of croup, and viral cultures and rapid antigen testing have minimal impact on management 2
- A careful history and physical examination is necessary to confirm the diagnosis of croup and rule out potentially serious alternative causes of upper airway obstruction 3
Diagnostic Criteria for Pertussis (Whooping Cough)
- Typical symptoms of pertussis include paroxysmal cough with characteristic whoop and vomiting 4
- Laboratory confirmation can be performed by isolation, detection of genomic DNA or specific antibodies 4
- PCR is a useful tool for pertussis diagnosis, particularly in pre-vaccinated infants 5
- Clinical criteria have no significant association with infection in recently and post-vaccinated children, and the yield of culture and serology is limited, especially among pre- and recently vaccinated children 5
- A variety of laboratory tools are available to aid in the diagnosis of pertussis, including culture, direct fluorescent antibody testing, PCR, and paired and single serology techniques 6