Diagnostic Testing for Nasal Disease

Causes of Nasal Disease

The most common causes of nasal disease in dogs and cats include nasal neoplasia, fungal infection, foreign body inhalation, dental-related nasal disease, and idiopathic or inflammatory rhinitis. Clinical signs are common for all etiologies and include sneezing, nasal discharge (mucoid, purulent, or hemorrhagic), and possibly facial pain or asymmetry. Nasal foreign bodies, which usually result from vomiting or regurgitation of oral foreign bodies into the nasopharynx, are often recognized by an acute onset of clinical signs while the other disorders are usually associated with chronic clinical signs. Foreign bodies usually result in unilateral disease, neoplastic of fungal disorders are often unilateral initially and then become bilateral, and inflammatory nasal disease can be unilateral or bilateral.

Physical Examination Features

Physical examination features that can help narrow the differential list include assessment of nasal airflow, determination of ocular retropulsion, palpation of the soft palate and regional lymph nodes, and examination for abnormalities in facial structures or the nasal planum. In dogs, fungal infections (usually due to aspergillosis) typically result in increased or preserved nasal airflow, nasal depigmentation, and facial pain, while nasal tumors usually lead to loss of nasal airflow, asymmetric ocular retropulsion, and resistance to depression of the soft palate. These same changes can be found on physical examination in cats with nasal tumors, however they may also be found with nasal fungal infections, which in cats are usually associated with cryptococcosis. Cryptococcosis might be associated with signs of disease in other organs, such as the skin, central nervous system, or the fundus. Dogs or cats with idiopathic rhinitis usually have copious mucoid nasal discharge but no systemic signs.

Cryptococcal Latex Agglutination Titer (LCAT)

The only diagnostic blood test available for nasal disease is the cryptococcal latex agglutination titer (LCAT). This test is very sensitive and specific for the diagnosis of cryptococcosis in dogs and cats, and false positive tests are rare. In contrast to serology for Cryptococcosis, Aspergillus serology cannot be relied on for the diagnosis because of the relatively high rate of false negative results. A recent study in dogs revealed that the sensitivity of the AGID for documenting canine aspergillosis was 68% and specificity was 98% (with only one false positive). Positive and negative predictive values were 94% and 84%. Therefore, a positive serology can be taken as evidence that Aspergillus is the likely cause of nasal discharge, however a negative test does not rule it out. In idiopathic rhinitis of dogs and cats, blood tests for viral organisms or Bartonella spp. are not helpful in disease management since the role of these organisms in disease has not been established.
In animals presenting with nasal signs, various samples can be collected for analysis, including a nasal swab, deep nasal flush, nasal biopsy, or a sample from the frontal sinus. Depending on the disease being investigated and the analysis to be performed, sampling methodologies will provide a variable yield. [...]