CTSB and respiratory system disorder: <h4>Background</h4>Acute-phase proteins (APPs) change in concentration during systemic inflammation.<h4>Objectives</h4>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.<h4>Material and methods</h4>Serum samples of 102 cats with respiratory signs and 20 healthy control cats were prospectively collected and tested for SAA and Hp.