Median Hp levels were significantly higher in cats with UAD (2.41 g/L, IQR: 2.21-2.87 g/L; <i>p</i> = 0.001), neoplastic (2.45 g/L, IQR: 2.10-2.86 g/L; <i>p</i> < 0.001) and infectious lower airway or pleural space disease (2.60 g/L, IQR: 2.40-2.67 g/L; <i>p</i> < 0.001) compared with FLAD (1.76 g/L, IQR: 0.99-2.26 g/L). Here, HP is linked to urethra adenocarcinoma.