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This article has been cited by other articles in PMC. While the term precision relates to the concept of variation around a central value, imprecision is actually what is measured. If this is true then using the principle of analysis of variance components: 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. As alluded to above, EPA2 is generally used to verify that a method is performing as is claimed by the manufacturer.

If there is only one run per day, the Runs: Thus the variance of the daily means is:. Clinical and Laboratory Standards Institute.

Furthermore, EP5 q2 that the experiment is performed at two different concentrations. In EP5 there should be two runs on each day, where each run consists of two test samples.

Reproducibility is at the other extreme and refers to the closeness of agreement between results of successive measurements obtained under changed conditions dlsi, operators, calibrators, reagents, and laboratory. The assessment is performed on at least two levels, as precision can differ over the analytical range of an assay. Linnet K, Boyd JC. Selection and eo5 evaluation of methods with statistical techniques.

The report shows the total number of observations analysed, number of days analysed including the number of days excluded due xlsi outliers or missing values, runs per day, and replicates per run are shown.

To compare precision against a manufacturers claim: This period is intended for the experimenter to learn the experimental protocol, and also to put quality controls into place, and perform an initial evaluation of precision and other acceptance tests, e. Open in a separate window. On day 1 the mean of the three replicates was 1.

### Evaluating Assay Precision

The runs should be separated by at least two hours, or if they take very long time to perform, one run per cosi is acceptable. If two runs are observed then a List dataset with repeat-measures and replicates layout should be used to arrange the two runs and replicates for each run.

Journal List Clin Biochem Rev v.

You are viewing documentation for the old version 2. Enter Allowable imprecision as an absolute value, as a percentage of analyte concentration, or enter both values for a combination.

### Evaluation of Precision Performance (EP5-A2)

Australasian Association of Clinical Biochemists Website. Click Compare against and select Performance claim. If the pre-assigned concentration is not known, the mean is used as an estimate of the true concentration.

Elsevier Saunders; St Louis: When using quality control samples, these should be different to those used to ensure the instrument is in control at the time of the assessment. Summing the square of the differences gives a total of 0. Finally, we can calculate the total or within-laboratory SD s l using the equation:. The SD min and SD max values form a confidence interval for the precision estimate, hence the confidence interval is [2. The average of the two samples that form the run is marked with a red bar.

The between-runs and between-days precision estimates are also given on ep 10 and If you are using version 3. 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.

Instead total precision within a laboratory clai precision will be assessed. E5p procedure is available in the Analyse-it Method Evaluation edition.

We’ve been developing intuitive high-quality statistical software at an affordable price, backed up by fast friendly customer service for over 25 years We give below some of the main features of the EP5 guidelines, for a detailed description see the EP2-A2 document. If the p-value is significant the observed precision is outside the goal. Frequently asked questions What are the different editions?

## Evaluating Assay Precision

CLSI document EPA2 describes the protocols that should be undertaken by the user to verify precision claims by a manufacturer. EP5 also estimates the variance of the sum of the three errors, the e5p called within-laboratory precision. Each level is run in duplicate, with two runs per day over 20 days, and each run separated by a minimum of two hours. The dataset must contain at least two continuous scale variables containing the observations in replicate for a run of the method.

Within-Laboratory Precision Finally, we can calculate the total or within-laboratory SD s l using the equation: However, if the values achieved are greater than those reported by the manufacturer, a statistical test needs to be performed to determine whether this difference is statistically significant.

Support Center Support Center. A method measured on a continuous scale over a number of days, with one or two runs per day. Various materials may be used to complete the assessment with either protocol. For the purposes of this discussion reproducibility will not be considered, as it involves multiple laboratories. Click OK to run the test.