Serum procalcitonin as a diagnostic biomarker in dogs with bacterial respiratory diseases

Background: Procalcitonin (PCT) is a useful biomarker in humans in the identification of bacterial respiratory infections. Objectives: The aim of this study was to investigate the utility of serum PCT measurements as a diagnostic biomarker in canine bacterial lower respiratory tract diseases. Methods: PCT concentrations were measured in serum samples with an ELISA method previously validated for dogs. All dogs underwent thorough clinical examinations, and the diagnosis of respiratory disease was based on clinical and laboratory findings, diagnostic imaging, as well as cytology and bacterial culture of respiratory samples. PCT concentrations between different cohorts of dogs were compared with an ANOVA-model. Results: Sixty-two privately owned dogs with respiratory diseases, 25 with bacterial pneumonia (BP), 17 with bacterial bronchitis caused by Bordetella bronchiseptica (BB), and 20 with chronic bronchitis (CB) as well as 44 healthy controls were included in the study. Serum PCT concentrations in dogs with bacterial respiratory diseases (BP mean 51.8 ng/L +/- standard deviation [SD] 40.6 ng/L and BB mean 61.4 ng/L +/- SD 35.3 ng/L) were not significantly different when compared with dogs with a non-bacterial respiratory disease (CB mean 89.7 +/- SD 73.5 ng/L) or healthy dogs (mean 51.0 ng/L +/- SD 37.5 ng/L, p > .05 in all comparisons). Conclusions: These results indicate that despite being a valuable diagnostic, prognostic, and follow-up marker in humans with pneumonia, serum PCT concentrations are not elevated in dogs with bacterial respiratory diseases and, therefore, cannot be used as a diagnostic biomarker in dogs.