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Clsk feature is only available in GenEx Enterprise. The purpose of EP5 is to evaluate the precision of clinical laboratory measurement methods. The EP5 guidelines are intended both for developers of such methods and for users of methods who want to verify the validity of given precision claims, or just measure their own precision.
We give below some of e5 main features of the EP5 guidelines, for a detailed description see the EP2-A2 document.
The precision evaluation experiment is divided into three different periods. Device Familiarization Period is a period to learn the operation of equipment and preparation of samples required.
Evaluating Assay Precision
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. This period lasts until data are obtained without operational difficulty for five days. The measurements continue for another 15 days. Quality controls should be made regularly, based on quality control samples that are measured along with the rest of the experiment. Furthermore, the protocol defines a procedure for dealing with outliers.
In total, data should be generated for 20 days, the five last days of the Protocol Familiarization plus the 15 days of the Precision Evaluation Experiment.
CLSI EP5 1- & 2- run precision | Analyse-it®
In EP5 there should be two runs on each day, where each run consists of two test samples. The runs should be separated by at least two hours, or if they take very long time to perform, one run per day is acceptable.
Furthermore, EP5 recommends that the experiment is performed at two different concentrations. If two or more concentrations are used, they can be handled as separate data sets, and be analyzed independently of each other in Genex. We refer to the EP5-A2 document for details about the experiment protocol. Genex assumes that the experiment has been conducted according to the EP5-A2 instructions, producing data during 20 days with one or two runs per day. Genex will estimate the precision in the data by the statistical methods required by the EP5-A2 document.
The random error is modeled according to the hierarchical model. Where X drs is the measurement on day d in run r on sample s. The model assumes that all the U d are identically distributed, and similarly that the V dr are identically distributed and that the W drs are identically distributed.
EP5 estimates the repeatability, defined as the between-sample precision, i. EP5 also estimates the variance of the sum of the three errors, the so called within-laboratory precision. Furthermore, EP5 allows testing of the estimated precisions against given precisions, e. Using the EP5 module in Genex. The experiment produces a data set with one or two runs per day and two replicas per run.
The days and runs should be given as classification columns in the data input to Genex, as in the example. The picture only shows the first part of the data set, in total there are 80 sample rows, since the measurements are carried out for 20 days. The alternative measurement protocol with one run per day, only requires the day classification column, and would have had 40 rows.
The EP5 module is found by selecting the Quality Ctrl tab, and clicking on the button labeled EP5, shown below as the second button from the left.
The control panel for EP5. Use the menus to the right under Columns to tell Genex which classification column that corresponds to days, and which column corresponds to runs. If there is only one run per day, the Runs: The fields under manufacturers claimed precisions allow testing against a claimed precision.
Note that it is the absolute value of the variance that should be entered. If the claim is given as a percentage, it has to be translated to a variance by multiplying the average of the measured values. If testing against a claim is not desired, these fields can be left blank. After all fields have been 2a to appropriate values, press the run button to perform the analysis.
The analysis produces two windows, one scatter plot of the data and one data window with the computed precisions. This scatter plot displays the input data with the runs on the x-axis.
Each sample is displayed as a blue marker. The average of the two samples that form the run is marked with a red bar. The average of all measurements is shown on line 6. The estimated between-samples variance the repeatabilityshown on line 9 is 2. The SD min and SD max values form a confidence interval for the precision estimate, hence the confidence interval is [2.
Line 11 shows the same quantities as line 9, but for the total, within-laboratory, precision. The between-runs and between-days precision estimates are also given on lines 10 and Finally, the last two lines indicate whether the claimed precisions were consistent with the precision estimated from the measurements.