Microbiological diagnosis of invasive aspergillosis

Abstract

Background: Invasive aspergillosis is an important opportunistic fungal infection in highly immunocompromised patients. Clinical diagnosis of invasive aspergillosis remains difficult in that clinical signs and symptoms are nonspecific. Radiologic findings are not pathognomonic but can be suggestive. The isolation of aspergilli from a normally sterile environment, which lacks sensitivity, usually represents a problem. Blood cultures are of limited utility, because the recovery of Aspergillus species from blood cultures invariably represents contamination. Early diagnosis is critical to a medical treatment, but is difficult to achieve with current methods. Measurement of galactomannan and β-D-glucan can be used as an aid in the diagnosis of invasive aspergillosis and it might promote a favourable outcome. The use of polymerase-chain-reaction assay (PCR), although promising, is currently investigational. Conclusions: The verification of aspergillosis requires isolation and microscopic analysis of sterile material showing the fungal structures. Non-culture-based mycological tests, especially assays for the detection of Aspergillus galactomannan and β-D-glucan in serum, or Aspergillus galactomannan in BAL and cerebrospinal fluid specimens are fit to convey useful information and may enable a diagnosis of probable invasive aspergillosis. We may hope that PCR will be improved enough to overcome the limitations of current methods and be developed into a better diagnostic modality for this disease.