From the Guidelines
Testing for varicella pneumonia involves a combination of clinical evaluation, imaging, and laboratory tests, with PCR testing of respiratory specimens being the most sensitive method for detecting varicella-zoster virus (VZV) DNA 1.
Diagnosis Approach
The diagnosis typically begins with recognizing characteristic symptoms such as fever, cough, shortness of breath, and chest pain in a patient with active chickenpox (varicella) rash.
- A chest X-ray is essential and usually shows diffuse nodular or interstitial infiltrates throughout both lungs.
- CT scans may provide more detailed imaging if needed.
- Laboratory confirmation includes PCR testing of respiratory specimens (like sputum or bronchoalveolar lavage fluid) to detect VZV DNA.
- Serological tests for VZV antibodies (both IgM and IgG) can support the diagnosis, with IgM indicating recent infection.
- In some cases, bronchoscopy with lung tissue biopsy may be necessary, where histopathological examination can reveal characteristic viral inclusions.
- Viral culture of respiratory specimens, though less commonly used due to longer turnaround time, can also isolate the virus.
Importance of Early Diagnosis
Early diagnosis is crucial as varicella pneumonia can be severe, particularly in adults, pregnant women, and immunocompromised individuals, with prompt antiviral therapy (typically intravenous acyclovir 10 mg/kg every 8 hours for 7-10 days) being essential for treatment 1.
- The choice of diagnostic tests should be guided by the clinical presentation and the likelihood of varicella pneumonia.
- In patients with severe illness, invasive diagnostic techniques such as bronchoscopy with a protected brush catheter or bronchoalveolar lavage may be necessary to establish a definitive diagnosis.
- The use of quantitative cultures of bronchoscopic or other specimens from lower airways may also facilitate the distinction between colonizing bacteria and pathogens, although this requires specialized expertise and equipment 1.
From the Research
Testing for Varicella Pneumonia
To test for varicella pneumonia, several methods can be employed, including:
- Chest radiographs to show bilateral infiltrates, as seen in patients with varicella pneumonia 2, 3
- Laboratory tests such as enzyme-linked immunoassay to detect varicella zoster virus (VZV) immunoglobulin (Ig) G, IgM, and IgA antibody 4
- Direct fluorescent antibody to detect VZV antigen 4
- Polymerase chain reaction (PCR) to detect VZV DNA, which is a convenient and accurate method for diagnosing varicella disease, including varicella pneumonia 4
- PCR testing of skin lesion specimens, which remains a sensitive method for diagnosing varicella disease 4
- PCR of oral specimens, which can sometimes aid in diagnosis of varicella disease, even after the rash resolves 4
Radiological Techniques
Radiological techniques such as chest X-ray and CT scans can be used to analyze lung changes and determine the presence of pneumopathies in varicella patients 3. These techniques can help identify the types of lung changes according to X-ray presentation and changes on computed tomography.
Importance of Early Detection
Early detection and prompt treatment of varicella-related complications, including varicella pneumonia, are crucial to reduce morbidity and mortality and improve overall clinical outcomes 2, 5. Intravenous acyclovir therapy should be instituted as early as possible in patients who may have varicella pneumonia 5.