The Role of Imaging
At the initial presentation of FN, a chest x-ray may be useful.
The yield of routine chest x-rays is low in asymptomatic neutropenic patients, but an initial x-ray provides a baseline to further examination 7.
It also might reveal some subtle indication of an infectious pneumonic process which could lead to further imaging using high resolution CT (HRCT) and possible indication for a broncho-alveolar lavage (BAL).
Patients with persistent FN are at increased risk for invasive fungal disease (IFI) and are usually started on antifungal therapy at 3-5 days of fever.
The standard of care is now to perform a CT of the chest (+/- sinuses) at the time of starting antifungal therapy.
This practice leads to an earlier diagnosis of IFI, in particular with molds, such as with invasive pulmonary aspergillosis (IPA).
Invasive pulmonary aspergillosis (IPA)
- Patients characteristically develop a “halo-sign” (Figure 2) on CT early in the first week of the disease 28.
- In a study of patients with IPA, 95% of subjects had characteristic halo-sign lesions on HRCT when chest x-ray showed either normal (29%) or non-specific findings (71%) 29.
- It is important to stress that the halo-sign is only present in the first week in IPA, and then progresses to be a non specific infiltrate if the CT is performed at a later stage.
Figure 2: CT scan of the chest in a 12 yo patient with AML and history of long standing neutropenia and 5 days of fever. Lesion displays characteristic “Halo-sign” feature of a macronodule surrounded by an area with a ground glass appearance. Patient was treated with voriconazole IV, then orally with good clinical response.
Confirmation of the diagnosis by percutaneous biopsy has also shown great specificity and susceptibility in paediatric patients in should be performed whenever it is possible 30.