It is essential to definitively diagnose nasal aspergillosis before starting treatment. As most of the available diagnostic
tests have limitations, a combination of tests is often necessary to confirm a diagnosis. These tests include serology, imaging
studies, rhinoscopy, cytologic and histologic examinations of affected tissues, and fungal culture. Before inducing anesthesia,
perform a complete blood count, serum chemistry profile, and urinalysis to rule out concurrent systemic disease.
Serology. Tests that can detect serum antibodies against Aspergillus species include agar gel immunodiffusion (AGID), complement fixation, and ELISA techniques. The antibodies detected with
AGID vary depending on the laboratory; however, most commercial laboratories detect antibodies to A. fumigatus, A. niger, and A. flavus.6 This test is widely available through veterinary diagnostic laboratories and is probably the most commonly performed fungal
serologic test at this time. However, a recent study indicated a test sensitivity of only 67% in dogs with sinonasal aspergillosis,
suggesting that one-third of affected dogs would have a negative result.7 This reduced sensitivity may be due to infection with a less common Aspergillus species. The test specificity was high at 98%, indicating that false positive results are unlikely. It is important to remember,
however, that a positive result with any serologic test does not eliminate the possibility of nonfungal rhinitis and is not
enough evidence for a definitive diagnosis of sinonasal aspergillosis.7
In human patients, a sandwich enzyme immunoassay (Platelia Aspergillus EIA—Bio-Rad Laboratories, Marnes-la-Coquette, France) has been used to confirm infection with Aspergillus species by the detection of a cell wall component called galactomannan. This component can be identified in serum and other body fluids such as cerebrospinal fluid or bronchoalveolar lavage fluid.8 Limited information is available on the reliability of antigen detection tests in veterinary medicine, but in a recent study,
the sensitivity of this test in dogs with sinonasal disease was only 23.5%.6 The poor sensitivity may reflect the noninvasive nature of this disorder, with limited release of antigens into the circulation.
A recent study evaluated the use of real-time broad-spectrum polymerase chain reaction test fungal DNA detection in whole
blood or tissue samples. Detection of fungal DNA in blood was of little diagnostic use because of low positive and low negative
predictive values, while identification of Penicillium and Aspergillus species DNA in nasal tissues lacked specificity for sinonasal aspergillosis.9
Imaging studies. All imaging studies should be completed before rhinoscopy and the collection of biopsy samples as hemorrhage can limit lesion
detection. Radiographs of the nasal cavity and frontal sinus can be diagnostically useful, but the patient must be anesthetized
during the radiographic examination to permit proper positioning. Ideally, lateral, ventrodorsal (both open- and closed-mouth)
and rostrocaudal views should be obtained. Common radiographic changes associated with aspergillosis are areas of increased
radiolucency, which suggest turbinate destruction.10 Opacification of the nasal cavities and frontal sinuses may also be noted.