ABSTRACT
Detailed knowledge of biological variation can facilitate accurate interpretation of clinical pathology parameters. A recent biological variation study in Asian elephants (Elephas maximus) found that hematology parameters had high individuality, which suggests that population-derived reference intervals may be an insensitive diagnostic tool. In elephant medicine, sensitive hematology-related diagnostics are crucial for clinical decision-making, particularly in elephants at risk for elephant endotheliotropic herpesvirus hemorrhagic disease (EEHV-HD). The objective of this study was to assess biological variation of hematology parameters in African elephants to determine whether population-derived reference intervals are a sensitive diagnostic tool for interpreting results and to provide a useful alternative. Eight healthy African elephants had blood collected under behavioral training every other week for 8 wk. Complete blood cell count (CBC) analysis was performed in duplicate to assess analytical variation. Previous methods were used to determine between-individual variation, within-individual variation, index of individuality, and reference change values (RCV). This study found that most hematology parameters displayed intermediate-to-high individuality, which suggests that alternatives to population-derived reference intervals are necessary to detect pathologic changes. To test the results of our biological variation data, a case of EEHV-HD was retrospectively evaluated. Individual normal values and calculated RCV detected a clinically significant monocytopenia, leukopenia, and thrombocytopenia associated with EEHV2 viremia. However, none of these parameters fell outside a population-derived reference interval. This study highlights the utility of biological variation in clinical decision-making and demonstrates that individual normal values and RCV may be important diagnostic tools for CBC interpretation in African elephants.
