Serum acute phase protein concentrations in dogs with spirocercosis and their association with esophageal neoplasia - a prospective cohort study.

Spirocerca lupi, the dog esophageal worm, typically induces formation of esophageal nodules, which may transform to sarcoma. Ante mortem discrimination between benign and malignant esophageal masses is challenging. Serum acute phase proteins (APPs) are utilized in diagnosis and prognosis of various canine diseases as markers of inflammation. This study characterized serum APPs concentrations in dogs with benign and malignant esophageal spirocercosis and evaluated their accuracy in differentiating benign from malignant lesions. Seventy-eight client-owned dogs with esophageal spirocercosis were included. Serum C-reactive protein (CRP), haptoglobin, serum-amyloid A (SAA) and albumin concentrations were measured upon diagnosis and follow-up visits, and compared with healthy dogs, and between malignant and benign cases. Haptoglobin, CRP and SAA concentrations were higher, and albumin concentration was lower (P<0.001 for all) in infected dogs compared to healthy controls. Dogs with suspected neoplasia had significantly higher CRP (P=0.011), haptoglobin (P=0.008) and SAA (P=0.05), and lower albumin (P=0.012) concentrations compared to dogs with benign esophageal nodules. APPs moderately discriminated between suspected malignant and benign esophageal disease. None of the dogs with suspected neoplasia had concurrent normal concentrations of all APPs. The present results indicate that canine spirocercosis is characterized by an acute phase reaction, both at presentation and during treatment. When concentrations of all four APPs are within reference range, esophageal malignancy is highly unlikely. Although concentrations of all positive APPs were significantly higher in suspected neoplastic cases compared to benign ones, moderate discriminatory power limits their clinical use. Neither APP was useful to monitor response to treatment.