There is no single test that will conclusively confirm whether a cat is coughing, wheezing or having other breathing difficulties because it has asthma or some other respiratory condition. The attending veterinarian presented with such a cat most likely will conduct a thorough physical examination and take a full history from the cat’s owner about its medical history and the onset and nature of its present symptoms. But further diagnostics will almost certainly be necessary to make a definitive determination as to the causes of the cat’s condition.
The veterinarian must rule out other disorders that could cause or contribute to the cat’s respiratory symptoms. These might include pneumonia, bronchitis, ingested hair balls, cancer, heartworm infection or lung parasites, among other things. The results of routine blood work (a complete blood count and serum biochemistry profile) and a urinalysis typically are normal in asthmatic cats, although certain white blood cells called eosinophils may be elevated if heart or lung parasites are present. Other laboratory tests, such as fecal flotation and heartworm testing, may be helpful if parasites are involved. Allergy tests, called intradermal skin tests, have not proven promising in helping to identify the cause(s) of asthma in cats.
Chest X-rays (thoracic radiographs) are extremely important when trying to diagnose the cause of feline asthma. Chest films can reveal inflammation, infection or scarring of the lungs, or they may be normal. The presence, absence or severity of any radiographic changes does not always correlate with the seriousness of a cat’s asthma. An echocardiogram (ECG) can be used to detect heartworm infection or other possible heart involvement. This is a non-invasive test that most cats tolerate quite well, although sedation may be necessary to quiet the cat for this procedure.
Other, more advanced tests that may help to confirm or rule out feline asthma include transtracheal wash (TTW), bronchoalveolar lavage (BAL) and bronchoscopy. A urine evaluation can be done to assess the cat’s overall health and organ function. The samples obtained through TTW, BAL and/or bronchoscopy are assessed microscopically through a procedure called cytology, where a veterinary pathologist or pathology technician analyzes the samples at a cellular level. If abnormal levels of bacteria are found, they can be cultured (grown) in the laboratory so that an appropriate antibiotic can be prescribed. Lung biopsy is also available, although it is rarely used in cats because it is so invasive and usually isn’t necessary. Sometimes, a positive response to treatment with medication will help to confirm a diagnosis of asthma, when other tests are inconclusive. Fortunately, feline asthma typically can be treated successfully, although it may require lifelong medical therapy.
Owners should keep notes of when their cats show signs of asthma, and the nature and extent of those signs. This can be quite helpful to the cat’s veterinarian, especially if there is any seasonality of the cat’s symptoms that might be due to seasonal exposure to the offending allergens.