Imagine this clinical scenario: you examine a four-year-old cat with a recent history of intermittent coughing, acute wheezing and respiratory difficulties. You investigate bloodwork, thoracic radiography and bronchoalveolar lavage, which reveal an eosinophilia, bronchial pattern and eosinophilic infiltrate, respectively. You diagnose the patient with feline asthma and decide to treat it with glucocorticoids; however, you are unsure whether oral therapy or inhalant therapy is most effective at controlling clinical signs. You decide to consult the evidence to find the answer.
The evidence
Three studies were critically reviewed. These were a randomised prospective non-blinded clinical pilot trial (Verschoor-Kirss et al., 2021), a randomised prospective crossover clinical trial (Leemans et al., 2012) and a randomised prospective placebo-controlled crossover study (Reinero et al., 2005).
Verschoor-Kirss et al. (2021) observed nine naturally asthmatic cats that had not previously received treatment. The cats were randomly allocated to two study groups: one group received oral prednisolone, while the other received oral prednisolone and inhaled fluticasone. The outcomes evaluated were:
- Changes on thoracic radiography
- Lung function testing
- Total nucleated cell count and percentage of eosinophil count from bronchoalveolar lavage (BAL) samples
- Serum fructosamine and serum allergy testing
Leemans et al. (2012) observed six cats with experimentally induced asthma sensitised to the Ascaris suum allergen. The authors induced feline asthma in all six cats via intramuscular injections of A. suum. In a crossover design, oral prednisolone, a combination of inhaled fluticasone propionate and salmeterol, fluticasone propionate via inhaler and no treatment were administered. Thoracic radiological assessment, lung function and airway responsiveness, haematology and matrix metalloproteinase analysis, bronchoscopic findings and BAL fluid assessment were all studied.
Reinero et al. (2005) observed six cats sensitised to Bermuda grass allergen (BGA). Feline asthma was induced in each cat via subcutaneous administration of BGA. All cats were then exposed to prednisone, inhaled flunisolide, an LT-receptor antagonist, an antiserotonergic and a control substance. The outcomes studied included:
- Airway resistance
- Percentage of eosinophils in BAL fluid
- Blood lymphocyte phenotype
- Serum content of allergen-specific immunoglobulin E
- Serum and BAL fluid content of allergen-specific immunoglobulin E and immunoglobulin A
Limitations of the evidence
The quality of the evidence to support the research question is weak. All three papers studied had limitations. They all had small sample sizes and short durations. Additionally, none of the studies are directly comparable due to differences in study population type and drug regimens. All studies also had weaknesses in their study design.
The quality of the evidence to support the research question is weak. All three papers studied had limitations
Verschoor-Kirss et al. (2021) had the following additional weaknesses: lack of placebo group, providing inhalant and oral treatment and findings that are potentially unrepresentative of asthmatic cats due to the lung function testing approach.
Leemans et al. (2012) lacked a crossover evaluation of untreated cats. Further, findings from experimental asthma induction may not accurately reflect naturally asthmatic cats, and there were thoracic radiography weaknesses (no sedation and limited views were taken). Reinero et al. (2005) also studied a disease model that may not reflect all facets of natural asthma.
Summary of findings
All the examined papers found oral or inhalant therapy using glucocorticoids resulted in a reduction in airway eosinophilia, with no significant differences between the two administration methods. However, we must consider this in the context of the limitations outlined above, which weaken the strength of these findings.
All the examined papers found oral or inhalant therapy using glucocorticoids resulted in a reduction in airway eosinophilia, with no significant differences between the two administration methods
Verschoor-Kirss et al. (2021) found that 3/4 (75 percent) of the cats on oral therapy reached the therapeutic target point for eosinophilia, compared with 2/5 (40 percent) of the cats treated with inhalant therapy. Improvement in airway resistance was more notable in cats treated with oral therapy, though the baseline resistance was higher in this group. Cats treated with both therapies were observed to have improved lung function and airway eosinophilia.
Leemans et al. (2012) found no significant difference in lung function and airway responsiveness between treatment groups. All medications caused a reduction in BAL fluid eosinophil percentage, with the oral and combined treatments causing a significant reduction.
Reinero et al. (2005) found that airway resistance was not consistently reduced by any of the drugs administered. However, cats that received oral prednisolone or inhaled flunisolide had a significantly reduced mean percentage of eosinophils in BAL fluid compared to the control group.
Conclusion
There is weak evidence to suggest equal treatment efficacy of oral and inhaled glucocorticoid therapy for the management of feline asthma. However, it must be noted that the quality of evidence across all papers studied was weak, and none of them addressed the research question directly.
There is weak evidence to suggest equal treatment efficacy of oral and inhaled glucocorticoid therapy for the management of feline asthma
Stronger evidence is required to verify these findings. This could be achieved by carrying out a well-designed randomised double-blinded placebo-controlled trial with an adequate sample size that focuses solely on the differences in the efficacy of treating cats with oral glucocorticoids versus inhalant glucocorticoids.
| The full Knowledge Summary can be read in RCVS Knowledge’s open access journal Veterinary Evidence. |
Disclaimer
The application of evidence into practice should take into account multiple factors, not limited to individual clinical expertise, patient’s circumstances, owner’s values, the individual case in front of you, the availability of therapies and resources, and the country, location or clinic where you work.
Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.
