1- & 2- precision over days, CLSI-EP5. This procedure is available in the Analyse -it Method Evaluation edition. Precision determines the variation of a method. NCCLS document EP5-A2 (ISBN ). NCCLS, West Valley Road, Suite , Wayne, Pennsylvania USA, THE NCCLS . Buy CLSI EP5 A2 Ed. 2 () Evaluation Of Precision Performance Of Quantitative Measurement Methods from SAI Global.

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Patient samples, reference materials, proficiency testing samples, or control materials may be used as the test samples, provided there is sufficient sample material for testing each sample five times per run for five to seven runs.

Note, some authors refer to total variation as just the between-run component instead of combined between-run and within-run shown above. However, for a method developed in-house a higher level of proof is required to validate the method, in which case EPA2 would be the appropriate guideline to use. Goal total and repeatability precision, calculated from the claim using the concentration level, and hypothesis tests to test if the observed precision is within the claim are shown.

Enter Allowable imprecision as an absolute value, as a percentage of analyte concentration, or enter both values for a combination. If the estimated bias is less than allowable bias, the bias is acceptable. National Center for Biotechnology InformationU.

CLSI EPA3: verification of precision and estimation of bias – Westgard

Introduction Part of the process of verifying or validating a method to confirm that it is suitable for use is an assessment of precision.

Total allowable error can be specified in absolute units of the analyte, as a percentage of analyte concentration, or as a combination of the two in which case the larger of the absolute and percentage level is used. The most significant change is the creation of a relatively simple experiment that gives reliable estimates of a measurement procedure’s imprecision and its bias.


Here’s a brief description of the protocol. If the p-value is significant the observed precision is statistically worse than the claim. As alluded to above, EPA2 is generally used to verify that a method is performing as is claimed by the manufacturer. When evaluating the precision of an assay, the trivial approach for estimating repeatability for any given level is to perform 20 replicate analyses in a single run on a single day.

If the calculated standard deviations are less than the published values, the user has verified the claim. ISSN — The contents of articles or advertisements in The Clinical Biochemist — Reviews are not to be construed as official statements, evaluations or endorsements by the AACB, its official bodies or its agents.

Privacy policy Contact us. There is some variation in the terminology used but for the purposes of this discussion, repeatability, also known as within-run precision, is defined as the closeness of agreement between results of successive measurements obtained under identical conditions.

Guest Essay

Part of the process of verifying or validating a method to confirm that it is suitable for use is an assessment of precision. The following example relates to the verification of performance of calcium according to EPA2 using a five day protocol.

Comparing against a performance claim Total precision within device or laboratory and repeatability within run can be compared against a manufacturer’s claim to demonstrate a method is operating correctly.


Save and re-apply filters Read the blog post. If the measurement procedure’s imprecision reported in publications, such as the manufacturer’s stated imprecision, does not meet the criterion, the precision verification procedure described in EPA3 is not appropriate.

If QC material is being used for the precision assessment, it should be different to that used to control the assay. Various materials may be used to complete the assessment with either protocol. First, users rarely have access to the measurement procedure used by the manufacturer or authors of a publication as the comparative method for the published bias.

There should be at least one quality control QC sample in each run. Sometimes the calculated standard deviations may exceed the published values, and yet the true standard deviations are less than the published values. If left blank Analyse-it will use the mean of all observations as an estimation of the true concentration.

Use of these materials is important in establishing the traceability of measurement procedures. Estimation of Repeatability and Within-Laboratory Precision The following lcsi relates to the verification of performance of calcium according to EPA2 using a five day protocol.

If this is true then using the principle of analysis of variance components: The dataset must contain at least two continuous scale variables containing the observations in replicate for a run of the method.

Repeatability Repeatability is estimated using the equation below.