Serum Thymidine Kinase 1, Canine-C-Reactive Protein, Haptoglobin, and Vitamin D Concentrations in Dogs with Immune-Mediated Hemolytic Anemia, Thrombocytopenia, and Polyarthropathy

Background: Relapses of immune-mediated hemolytic anemia (IMHA), thrombocytopenia (ITP), or polyarthropathy (IMPA) occur despite normal hematologic and cytologic parameters. Thymidine kinase 1 (TK1), canine C-reactive protein (c-CRP), haptoglobin (HPT), and 25-Hydroxyvitamin-D (25(OH)D) might be adjunct to current monitoring strategies. Hypothesis/Objectives: Compare serum concentrations of TK1, c-CRP, HPT, and 25(OH) D in dogs with well-and poorly controlled primary IMHA, ITP, or IMPA. Animals: Thirty-eight client-owned dogs. Methods: Prospective descriptive study. Dogs diagnosed with IMHA, ITP, or IMPA had serum biomarker concentrations measured commercially. Disease control was assessed by hematocrit/PCV and reticulocyte count, platelet count, and synovial fluid cytology for IMHA, ITP, and IMPA, respectively. Statistical analysis performed by Mann-Whitney rank-sum tests and receiver operating characteristic curves. Results: TK1 and c-CRP, but not HPT significantly decreased with well-versus poorly controlled IMHA (P = 0.047, P = 0.028, P = 0.37). C-CRP, but not TK or HPT was significantly lower with well-versus poorly controlled IMPA (P = 0.05, P = 0.28, P = 0.84). Sensitivity and specificity of TK and c-CRP (simultaneously) for detecting dogs with poorly controlled IMHA were 88 and 100%, respectively. Sensitivity and specificity of c-CRP for detecting poorly controlled dogs with IMPA were 13 and 100%, respectively. 92% of dogs were vitamin D insufficient (<100 ng/mL) regardless of disease control. Conclusions and Clinical Importance: Combining TK1 and c-CRP might act markers of disease control in dogs with IMHA. Canine-CRP cannot be recommended as an independent marker of disease control in IMPA. 25(OH) D insufficiency in immune-mediated disorders might benefit from further study to determine if supplementation could improve therapeutic response or reduce disease risk.