1. 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

2. 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

3. 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’

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

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

12. 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

13. 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.

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

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

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

17. E-mail: kathy-freeman@talktalk.net
ECVCP
Thank You!
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