Validation of a point-of-care clinical chemistry analyser generation of clinical chemistry reference intervals and evaluation of serum protein electrophoresis in the southern white rhinoceros Ceratotherium simum simum

Abstract

The southern white rhinoceros, Ceratotherium simum simum, is heavily poached in southern Africa, with over 4 000 animals killed in South Africa between 2013 and the end of 2016. White rhinoceros that survive poaching attempts, or those that are wounded during fighting, require veterinary care for their injuries. Both injured and orphaned rhinoceros also require veterinary care during the process of rehabilitation and return to the wild. Clinical pathology plays an important role in the initial evaluation and ongoing monitoring of these animals, but it can only become a truly useful tool for this species if wildlife veterinarians have access to validated analytical methods and accurate reference intervals. The broad objectives of this study were therefore to 1) validate a point-of-care clinical chemistry analyser for use in the white rhinoceros, and assess its performance under field conditions; 2) generate clinical chemistry reference intervals on the point-of-care analyser, and a reference laboratory analyser, for the white rhinoceros; and 3) explore serum protein fractions in both healthy and injured white rhinoceros. Best-practice guidelines for method validation, quality control and reference interval generation, as published by the American Society for Veterinary Clinical Pathology, were followed throughout. The IDEXX VetTest was selected as the point-of-care analyser. Method validation was performed by assessing differences between white rhinoceros heparin plasma and serum, short-term imprecision, long-term imprecision and reportable range. The VetTest was found to be suitable for use in the white rhinoceros, although imprecision was high for alkaline phosphatase (ALP), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) at low activities, and the reportable range for AST and lactate dehydrogenase (LDH) differed from the manufacturer’s specifications. Statistical quality control methods were used to develop a quality control strategy for the analyser and this protocol was used to evaluate the performance of the VetTest under typical field conditions. Eleven analytes were suitable for statistical quality control using the 13s rule, three using the 2s rule; ALP was not suitable. In the field, the observed analytical error was less than the allowable analytical error for all fifteen analytes and sigma metric values were >3.0 for twelve analytes. This study showed that statistical quality control protocols are useful for monitoring the performance of point-of-care analysers, and that the VetTest can be used out in the field for white rhinoceros. Clinical chemistry reference intervals are used as an indication of normal values in health, against which the results of ill animals are compared. These reference intervals should be not only species-, but also analyser-specific, as different analytical methods may produce different results. A method comparison study was carried out to assess analytical differences between the VetTest and the Roche Cobas Integra 400 Plus, using white rhinoceros plasma. Significant differences were found for all of the ten analytes examined. Separate reference intervals were subsequently generated for each analyser from 51 healthy wild rhinoceros. Noteworthy findings from this study were the low ALT activity and high total protein and globulin concentrations in this species.