Reference intervals for hematology and plasma biochemistry and comparison with selected estimation methods in Northern boobooks (Ninox japonica ) undergoing rehabilitation

Abstract

The establishment of reliable physiological baselines is essential for the clinical diagnosis and treatment of rescued wildlife, but reference intervals (RIs) are limited for many species encountered in rehabilitation settings. The Northern boobook (Ninox japonica) is one of the most frequently rescued owl species at wildlife rescue centers in the Republic of Korea, yet veterinary research on this species is scarce. This study aimed to establish the hematologic and plasma biochemical RIs for rehabilitated Northern boobooks and assess the agreement between field estimation methods and standard analytical techniques for selected variables. These variables included hemoglobin (Hgb) derived from packed cell volume, total protein (TP) measured by refractometry, and total white blood cell (TWBC) counts obtained from blood films. The blood profiles for RI calculation were collected from 41 clinically normal, rehabilitated individuals, and no statistically significant differences were found between the sexes for any parameter. Method comparison analyses for Hgb, TP, and TWBC found significant differences between the estimation techniques and their respective reference methods. The Bland–Altman plots found systematic biases for all methods, because the 95% confidence interval for mean biases excluded zero, indicating poor concordance. Passing–Bablok regression further confirmed systematic deviations, identifying a mix of constant and proportional biases that varied among the analytes. These findings underscore the need for caution when interpreting the estimated values in clinical settings. In addition, because rehabilitated individuals may appear clinically stable while harboring subclinical pathologies, the results of this study should be considered within the context of rehabilitation.