Nucleated red blood cells for characterization of systemic inflammatory response syndrome in dogs

Abstract Background Nucleated red blood cells (nRBCs) are increased by disease processes and hematopoietic stress. Objectives To evaluate the utility of nRBCs as a marker of disease severity and prognosis in dogs with systemic inflammatory response syndrome (SIRS). Animals Sixty‐two client‐owned dogs met the criteria of SIRS without anemia. Methods nRBC‐positive (nRBCs: ≥5/500, n = 32) and nRBC‐negative (nRBCs: <5/500, n = 30) dogs were classified, and clinicopathological data, Acute Patient Physiologic and Laboratory Evaluation (APPLEfast) scores, cytokines, 2‐ and 4‐weeks survival were compared. Results The median WBC (17.63, interquartile range [IQR]: 11.72‐20.24 × 109/L), neutrophils (12.28, IQR: 7.17‐16.88 × 109/L), band neutrophils (1288.5, IQR: 252.5‐2575 cells/μL), serum IL‐6 (731.80, IQR: 299.79‐5522.05 pg/mL), and plasma C‐reactive protein (4.10, IQR: 1.00‐8.58 mg/L) were significantly higher in nRBC‐positive dogs than negative dogs (11.27, IQR: 7.63‐15.13 × 109/L; 7.57, IQR: 4.96‐11.71 × 109/L; 62.5, IQR: 0‐350.25 cells/μL; 232.30, IQR: 99.33‐447.01 pg/mL; 0.40, IQR: 0.10‐3.00 mg/L, respectively; P < .05). The median reticulocyte count (87.95, IQR: 52.45‐130.55 × 103/μL) and serum IL‐3 (40.94, IQR: 29.85‐53.52 ng/L) were also significantly greater in nRBC‐positive dogs than nRBC‐negative dogs (46.00, IQR: 26.43‐68.15 × 103/μL; 25.24, IQR: 21.65‐37.40 ng/L, respectively; P < .01). The presence of circulating nRBCs, but not the reticulocyte count, at admission was predictive of death in dogs with SIRS at 2 weeks (P = .01, AUC: 0.729) and 4 weeks (P = .002, AUC: 0.731). The overall survival time was shorter in nRBC‐positive dogs (95% CI, 47.35‐113.90) than nRBC‐negative dogs (95% CI, 90.92‐135.55; P = .03). Conclusions and Clinical Importance Measuring peripheral nRBCs in dogs with SIRS is rapid and clinically applicable, reflecting disease severity and associated prognosis.