Procollagen type III amino terminal propeptide concentrations in dogs with idiopathic pulmonary fibrosis compared with chronic bronchitis and eosinophilic bronchopneumopathy

Idiopathic pulmonary fibrosis (IPF) is characterised by an abnormal accumulation of collagen type III in the pulmonary interstitium. Procollagen type III amino terminal propeptide (PIIINP) is used as a marker of collagen type III synthesis. In this study, the concentrations of PIIINP were investigated in dogs with IPF (n = 15), dogs with chronic bronchitis (CB, n = 19), dogs with eosinophilic bronchopneumopathy (EBP, n = 13) and healthy dogs (n = 25). PIIINP concentrations in serum and bronchoalveolar lavage fluid (BALF) were analysed by radioimmunoassay. Serum PIIINP values did not differ between groups, indicating that serum PIIINP is not useful in evaluating respiratory diseases in dogs. BALF PIIINP was significantly elevated in dogs with IPF compared with healthy dogs (P = 0.002) and dogs with CB (P < 0.001). BALF PIIINP was significantly higher in dogs with EBP than in dogs with CB (P = 0.003) or healthy dogs (P = 0.022). There were no differences in BALF PIIINP concentrations between dogs with IPF and dogs with EBP or between dogs with CB and healthy dogs. These results indicate that IPF is associated with elevated BALF PIIINP concentrations. BALF PIIINP concentrations also are elevated in EBP, possibly due to secondary fibrotic changes.