Investigations
1st investigations to order
FBC with differential
Test
Described in majority of patients in case series.
Result
leukopenia or normal WBC; lymphopenia; thrombocytopenia
LFTs
Test
Described in majority of patients in case series.
Result
elevated aspartate aminotransferase/alanine aminotransferase
chest x-ray
Test
A chest x-ray alone cannot exclude or differentiate viral or bacterial pneumonia.
Lung infiltrates are commonly bilateral, diffuse (lower, middle, and upper zones can be affected), and show both central and peripheral distribution.[122]
Result
may be normal; may show infiltrates consistent with pneumonia in severe cases
pulse oximetry
Test
Indicated in patients with dyspnoea or suspected pneumonia.
Result
may show hypoxia
sputum Gram stain
Test
Primary bacterial pneumonia and potential bacterial co-infection should be evaluated. Co-infections have been reported in Asian lineage A(H7N9) virus-infected patients, but mainly hospital-acquired bacterial infections and ventilator-associated pneumonia.
Result
visualisation of infecting organisms if bacterial pneumonia or potential bacterial co-infection
sputum and blood bacterial culture
Test
Primary bacterial pneumonia and potential bacterial co-infection should be evaluated in severely ill patients.
Result
growth of infecting organism if bacterial pneumonia or potential bacterial co-infection
reverse transcription polymerase chain reaction (RT-PCR)
Test
Recommended for diagnosis of Asian lineage A(H7N9) virus infection. Should be performed in patients with signs or symptoms consistent with influenza-like illness or acute respiratory tract infection who have a relevant epidemiological history.[111][115][116][117][118]
Infection prevention and control precautions are recommended when collecting specimens. Preferred specimens in non-intubated patients are upper respiratory tract specimens (e.g., oropharyngeal swab, nasopharyngeal swab, nasal aspirate or wash). Preferred specimens in intubated patients or patients with severe lower respiratory tract illness are lower respiratory tract specimens (e.g., endotracheal aspirate, bronchoalveolar lavage fluid). Multiple respiratory specimens should be collected from different sites on at least two consecutive days for hospitalised patients. Swabs with a synthetic tip (e.g., Dacron®, polyester) or an aluminium or plastic shaft should be used. Obtain specimens as soon as possible, ideally within 7 days of symptom onset.[111]
RT-PCR for A(H7N9) viruses is usually not available in many clinical settings, where detection of non-subtyped influenza A virus is more typical. Many regional public health laboratories, most national laboratories, and some private laboratories can perform RT-PCR for A(H7N9) virus, or RT-PCR for avian A(H7) viruses with subsequent virus characterisation by genetic sequencing. If subtyping of a detected influenza A virus has been attempted locally, but seasonal A(H1) and A(H3) viruses could not be detected ('unsubtypable influenza A'), the sample should be referred to a reference laboratory for further characterisation.
May take several hours to produce preliminary results, but transport time and testing logistics may delay testing results.
Result
positive for H7-specific viral RNA
Investigations to consider
viral culture
Test
Virus culture will not produce timely results for clinical management and must be performed in a biosafety level 3-enhanced (BSL 3+) laboratory. Viral culture can be performed at World Health Organization (WHO) avian influenza reference laboratories and WHO collaborating influenza centres.
Viral culture is important for virological surveillance, antigenic monitoring for vaccine strain selection, and assessment and analyses of viral characteristics such as genetic reassortment, receptor binding affinity, and antiviral susceptibility.
Clinical specimens testing positive for A(H7N9) virus RNA by reverse transcription polymerase chain reaction may be cultured by a WHO avian influenza reference laboratory or WHO collaborating influenza centre laboratory.
Result
positive for A(H7N9) virus
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