A measured or observed laboratory test result from a person (usually a patient) is compared with a reference interval for the purpose of making a medical diagnosis, therapeutic management decision, or other physiological assessment. It is important to develop reference intervals using a systematic process that takes into account the various influences on the measured laboratory test results.
Clinical and Laboratory Standards Institute (CLSI) recently published a document, Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Proposed Guideline–Third Edition (C28-P3), which offers a protocol for determining reference intervals that meet the minimum requirements for reliability and usefulness. The guideline focuses on health-associated reference values as they relate to quantitative clinical laboratory tests. Included are various requirements for studies to determine reference values for a new analyte or a new analytical method of a previously measured analyte. Also discussed is the transfer of established reference values from one laboratory to another.
Once approved, this document will replace the approved standard, C28-A2, which was published in 2000, and includes the following updates:
for some analytes, reference intervals have been replaced by decision limits, established by national (or international) consensus;
reaffirmation of the recommendation that reference intervals be established by collecting samples from a sufficient number of qualified reference individuals to yield a minimum of 120 samples for analysis, by nonparametric means, for each partition (eg, sex, age range);
new emphasis on the ability of every individual laboratory to verify reference intervals established elsewhere, a process requiring samples from as few as 20 reference individuals; and
introduction of recommendations regarding multicenter studies (to make it easier to collect large numbers of reference samples) and robust statistical methods (to make possible generation of reliable reference intervals with fewer than 120 samples).
This document is intended for diagnostic laboratories and diagnostic test manufacturers.
For additional information on CLSI or for further information regarding this release, visit our website at http://www.clsi.org or call +610.688.0100.
CLSI, formerly NCCLS, is a global, nonprofit, membership-based organization dedicated to developing standards and guidelines for the health care and medical testing community. CLSI’s unique consensus process facilitates the creation of standards and guidelines that are reliable, practical, and achievable for an effective quality system.
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