Serum PCT concentrations in dogs with bacterial diseases (BP mean 51.8 ng/L ± standard deviation [SD] 40.6 and BB mean 61.4 ± SD 35.3 ng/L) were not significantly different when compared to dogs with a non‐bacterial respiratory disease (CB mean 89.7 ± SD 73.5 ng/L) or to healthy dogs (mean 51.0 ± SD 37.5 ng/L, P > 0.05 in all comparisons). This evidence concerns the gene CALCA and bacterial infectious disease.