ECVCP Recommendations On Reference Values 2008 Practice Laboratory ECVCP Recommendations On Reference Values 2008 K. Freeman, S. Thoresen, A.L. Jensen, N. Bauer, T. Furlanello, S. Neumann (Members of the ECVCP Laboratory Standards Committee) 01/2002

Reference Values and Reference Intervals ‘the most widely used medical decision-making tool’ used as guidelines when there are no better means for distinguishing health and disease

Reference Values and Reference Intervals ’the purpose of reference values, and of the reference limits or intervals derived from them, is to provide a basis for interpreting laboratory results obtained in clinical settings’

Reference Values and Reference Intervals derivation and use should be based on clinical practice and need guided by considerations as to: the purpose of the test patient population being tested consequences of false negative or false positive results

Reference Values and Reference Intervals Disease status of the patient and likelihood of single or multiple problems that may result in changes in laboratory values

Reference Interval Challenges Multiple species and age groups Males, females, altered animals acquisition of specimens definition of the reference population adequate numbers of specimens identification and removal of outliers

Reference Interval Challenges determination of the need for partitioning of data type of statistical analyses to be performed and working knowledge and understanding of various statistical packages

ECVCP Recommendations (1) Information should be available to clients upon request (a) about the reference population, and its distribution (b) characteristics of the reference data (c)numbers of specimens used (d) statistical methods used to determine reference intervals

ECVCP Recommendations (2) Patient data may provide a source for reference values, provided there are sufficient numbers of specimens and rigorous exclusion criteria are applied

ECVCP Recommendations (3) Data should be scrutinized early in the process to determine if the distribution of data is Gaussian or not, whether Gaussian distribution can be obtained with data transformation, and, thus, whether parametric or non-parametric methods should be used

ECVCP Recommendations (4) Transference of reference intervals is acceptable (a) Population comparable (b) Instrument/method same (c ) Transference validation

ECVCP Recommendations (5) Transference of reference intervals for methods that differ also may be acceptable (a) using linear regression equation obtained from a comparative study (b) with validation

Quality Systems and Reference Intervals Periodic review of reference intervals often a requirement Careful consideration of how this should be accomplished is recommended. Changes or adjustments should have sound basis and veterinary input as to their validity and application.

Current and Future Concepts Reference values for nonhealthy patients Multivariate reference profiles LIMS applications for probability analyses Subject-based reference intervals

Current and Future Concepts Index of individuality Reference change values Refined statistical analyses

ECVCP Laboratory Standards Committee An honour to work with my colleagues in ECVCP Knowledgeable professionals dedicated to promotion of quality in veterinary laboratory testing

E-mail: kathy-freeman@talktalk.net ECVCP Thank You! Contact information: Home: +44 (0)1567 820 580 Mobile: +44 (0) 77 666 00274 Idexx Laboratory: +44 (0)1937 544 000 E-mail: kathy-freeman@talktalk.net