ASVCP reference interval guidelines: determination of de novo reference intervals in veterinary species and other related topics


  • Position Statements and Special Reports developed by the American Society for Veterinary Clinical Pathology (ASVCP) provide current information on topics in veterinary clinical pathology that are important to the veterinary community. The procedure for submitting statements is detailed at The ASVCP Executive Board is responsible for the review and approval of all statements, often following a period of input from the ASVCP membership and experts in the field. The final draft is then submitted to Veterinary Clinical Pathology and is edited prior to publication.


Dr. Kristen R. Friedrichs, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin–Madison, 2015 Linden Dr., Madison, WI 53706, USA



Reference intervals (RI) are an integral component of laboratory diagnostic testing and clinical decision-making and represent estimated distributions of reference values (RV) from healthy populations of comparable individuals. Because decisions to pursue diagnoses or initiate treatment are often based on values falling outside RI, the collection and analysis of RV should be approached with diligence. This report is a condensation of the ASVCP 2011 consensus guidelines for determination of de novo RI in veterinary species, which mirror the 2008 Clinical Laboratory and Standards Institute (CLSI) recommendations, but with language and examples specific to veterinary species. Newer topics include robust methods for calculating RI from small sample sizes and procedures for outlier detection adapted to data quality. Because collecting sufficient reference samples is challenging, this document also provides recommendations for determining multicenter RI and for transference and validation of RI from other sources (eg, manufacturers). Advice for use and interpretation of subject-based RI is included, as these RI are an alternative to population-based RI when sample size or inter-individual variation is high. Finally, generation of decision limits, which distinguish between populations according to a predefined query (eg, diseased or non-diseased), is described. Adoption of these guidelines by the entire veterinary community will improve communication and dissemination of expected clinical laboratory values in a variety of animal species and will provide a template for publications on RI. This and other reports from the Quality Assurance and Laboratory Standards (QALS) committee are intended to promote quality laboratory practices in laboratories serving both clinical and research veterinarians.