Plasma concentration of thrombopoietin in dogs with immune thrombocytopenia

Abstract

Abstract Background Immune thrombocytopenia (ITP) is a common cause of severe thrombocytopenia in dogs. The pathogenesis of nonassociative, primary ITP (pITP) appears complex, with ill‐defined thrombopoietic response. Objectives Develop an immunoassay to measure plasma canine thrombopoietin (TPO) concentration and characterize TPO concentrations in dogs with pITP. Animals Forty‐one healthy dogs, 8 dogs in an induced ITP model (3 control, 5 ITP), and 58 pITP dogs. Methods Recombinant canine TPO (rcTPO) was purchased and its identity confirmed by mass spectrometry. Monoclonal antibodies were raised to rcTPO and used to configure a sandwich ELISA using streptavidin‐biotin detection. Assay performance, coefficients of variability, and healthy dog plasma TPO reference interval (RI) were determined, followed by assay of ITP samples. Results Assay dynamic range was 15 pg/mL (lower limit of detection) to 1000 pg/mL TPO, with limit of quantitation of 62 pg/mL. Plasma TPO RI was 0 to 158 pg/mL, with plasma TPO 6000 pg/mL. In contrast, only 2/58 pITP dogs had TPO values above RI. Conclusions and Clinical Importance Plasma TPO concentration is paradoxically low at diagnosis for most dogs with pITP. This finding suggests that ineffective thrombopoiesis contributes to thrombocytopenia in pITP dogs and supports evaluating TPO receptor agonist treatment as used for pITP in humans. The TPO assay provides a new tool to study thrombopoiesis in pITP and other thrombocytopenic syndromes in dogs.

Keywords

• autoimmune disease
• blood platelets
• clinical pathology
• enzyme‐linked immunosorbent assay
• hematopoiesis
• hematopoietic growth factors