Evaluation of amyloid A and haptoglobin in the serum of cats with respiratory diseases.

Abstract

BACKGROUND: Acute-phase proteins (APPs) change in concentration during systemic inflammation. OBJECTIVES: To investigate serum concentrations of amyloid A (SAA) and haptoglobin (Hp) in various respiratory diseases in cats, and assess their potential to distinguish between different respiratory conditions. MATERIAL AND METHODS: Serum samples of 102 cats with respiratory signs and 20 healthy control cats were prospectively collected and tested for SAA and Hp. Cats were grouped based on conditions into feline lower airway disease (FLAD,=&#x202f;26), infectious lower airway or pleural space disease (=&#x202f;12), neoplastic lower airway or pleural space disease (=&#x202f;17), congestive heart failure (CHF,=&#x202f;29) and upper airway disease (UAD,=&#x202f;18). RESULTS: Median SAA concentrations were significantly higher in cats with infectious lower airway or pleural space disease (2.61&#x202f;&#x3bc;g/mL, IQR: 0.57-15.45&#x202f;&#x3bc;g/mL) compared to cats with FLAD (0.14&#x202f;&#x3bc;g/mL, IQR: 0.10-0.63&#x202f;&#x3bc;g/mL;<&#x202f;0.001). However, median values in all groups were within the reference range (< 6.7&#x202f;&#x3bc;g/mL) and did not significantly differ from healthy controls. Median Hp levels were significantly higher in cats with UAD (2.41&#x202f;g/L, IQR: 2.21-2.87&#x202f;g/L;=&#x202f;0.001), neoplastic (2.45&#x202f;g/L, IQR: 2.10-2.86&#x202f;g/L;<&#x202f;0.001) and infectious lower airway or pleural space disease (2.60&#x202f;g/L, IQR: 2.40-2.67&#x202f;g/L;<&#x202f;0.001) compared with FLAD (1.76&#x202f;g/L, IQR: 0.99-2.26&#x202f;g/L). Cats with UAD (<&#x202f;0.001), neoplasia (<&#x202f;0.001), infectious lower airway or pleural space disease (p&#x202f;<&#x202f;0.001) and CHF (2.31&#x202f;g/L, IQR: 0.84-2.57&#x202f;g/L;=&#x202f;0.002) showed significantly higher Hp values compared to healthy cats (1.25&#x202f;g/L, IQR: 0.81-1.83&#x202f;g/L) (reference range < 1.9&#x202f;g/L). CONCLUSION: SAA and Hp are not suitable for clearly differentiating between different respiratory conditions in cats. However, increased SAA levels are more indicative of infections of the lower airways or pleural space than of FLAD, which could be helpful for therapeutic considerations.