Diagnosis

The single most common (and frequently the only) clinical sign reported by caregivers is chronic coughing (Moise et al. 1989; Dye et al. 1996; Johnson and Vernau 2011; Lin et al.

In the mildly affected patient physical examination findings may be unremarkable. In more severely affected cats non-specific findings include respiratory distress, abnor­mal lung sounds (wheezing, crackles), tachypnea, and increased expiratory effort (Padrid 2014; Trzil and Reinero 2014).

In most instances, the diagnosis is usually a clinical one (i.e., there is no single confirma­tory test). A diagnosis is made by combining patient signalment, history, physical exami­nation, and diagnostic findings to complete a clinical picture (Reinero 2011; Lin etal. 2015). Excluding differentials is vital in the workup of the asthmatic patient. A full blood count may demonstrate eosinophilia in some cases, but this is neither specific nor sensitive for asthma. Fecal analysis is performed to look for parasites (Toxocara cati, Aelurostrongylus abtrusus) that may be associated with eosino­philic airway inflammation (Conboy 2009), and heartworm needs to be excluded in endemic areas. Thoracic radiographs remain the most readily available diagnostic tool; but is neither sensitive (up to 23% of cases may lack radiographic abnormalities) nor specific. It does, however, assist in ruling out differen­tials (Adamama-Moraitou et al. 2004). Thoracic ultrasound in the emergency setting is useful in excluding differentials causing respiratory distress and N-terminal pro-BNP can help distinguish congestive heart failure from primary respiratory disease. Bronchoscopy with broncho-alveolar lavage (BAL) for cytological evaluation, polymerase chain reaction (PCR) and culture is per­formed to exclude other airway diseases (e.g., bacterial bronchopneumonia, parasitic lung disease) (Johnson and Drazenovich 2007; Johnson and Vernau 2011).