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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Table 2 shows the results of each of these calculations.

Evaluating Assay Precision

Summary When evaluating the precision of a method it is necessary to assess the repeatability within-run and the total or within-laboratory precision.

As alluded to above, EPA2 is generally used to verify that a method is performing as is claimed by the manufacturer. For bias relative to the quality control peer group, quality control materials with peer group values for the measurement procedure are appropriate.

Please review our privacy policy. If the p-value is significant the observed precision is outside the goal. Finally, we can calculate the total or within-laboratory SD cpsi l using the equation:. Calculation of the verification interval would be complicated, clsii the committee simplified it greatly by providing tables for the difficult-to-calculate quantities based on the number of replicate measurements per run, the number of runs, and the uncertainty of the target value.

Acknowledge Committee Members The EPA3 document development committee was team of experts who worked together well. Goal total precision, calculated from the imprecision specification and the concentration level, and a hypothesis test to test if the observed precision is within the goal are shown.

Elsevier Saunders; St Louis: The Concentration if the pre-assigned concentration was specified and the Mean concentration lcsi all replicates are shown.

The width of the verification interval depends on the uncertainty of the target value of the reference material and the standard error of the calculated mean concentration from the experiment. If the mean concentration from the user’s experiment is within the verification interval, there is no statistically significant bias. Estimating Precision 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 user is interested in estimating bias relative to the peer group for proficiency testing, and wants to estimate how the measurement procedure will perform well on proficiency testing, proficiency testing materials with peer group values for the measurement procedure being evaluated are appropriate.

The assessment is performed on at least two levels, as precision can differ over the analytical range of an assay. Estimation of Bias Because the precision experiment has so wp5 replicate measurements, collected over several days, results e5p the precision experiment clso be used to make a reliable estimate of the bias of the measurement procedure relative to the assigned target values of the sample materials used in the experiment.

Evaluating Assay Precision

Enter Total and Repeatability precision as absolute values, as percentages of analyte concentration, or as a combination, from the manufacturer’s claims. Internationally recognized high order reference materials, such as a material from c,si U. To allow for this possibility, the user calculates a “verification limit” based on the published standard deviation and the size of the user’s experiment.

Privacy policy Contact us. 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. If the pre-assigned concentration is not known, the mean is used as an estimate of the true concentration. If QC material is being used for the precision assessment, it should be different to that used to control the assay.

Each level is run in duplicate, with two runs per day over 20 days, and each run separated by a minimum of two hours. Using the example data and assuming the claimed repeatability is an improbable CV of 1. The reader is referred to the CLSI documents for details. Cclsi example, if the true standard deviations were actually exactly equal to their claimed counterparts, the calculated standard deviations would exceed their published counterparts fifty percent of the time in verification experiments.

The first step is to calculate the mean of the replicates for each day, then for each result subtract the mean for that day and square the resultant value. The report shows the total number of observations analysed, number of days analysed including the number of days excluded due to outliers or missing values, runs per day, and replicates per run are dlsi. The user must evaluate the estimated bias versus allowable bias.


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Repeatability Repeatability is estimated using the equation below. For new licenses Buy new licence Clsk prices, get a quote, or purchase online or through an authorised reseller. This article has been cited by other articles in PMC.

There were two problems with this approach. If this is true then using the principle of analysis of variance components:. The powerful statistical analysis you’d expect from an expensive statistics package.

What are perpetual vs annual licenses What is per-user vs floating-user licenses What is maintenance? Unfortunately this approach is insufficient, as it tends to under-estimate repeatability, as the operating conditions in epp5 at the time may not reflect usual operating parameters.

The document includes tables to simplify the calculation of the verification limit. Evaluation of precision performance of quantitative measurement methods. The EPA3 document development committee was team of experts who worked together well.

Evaluation of Results As alluded to above, EPA2 is generally used to verify that a method is performing as is claimed by the manufacturer. If the p-value is significant the observed precision is statistically worse than the claim. T is best calculated in a spreadsheet and is given by:.

Latest blog post Analyse-it 5. Previous versions of EP15 included a small comparison experiment, involving 20 patient samples, which was to be used to verify a manufacturer’s claimed bias. Statistical process control and quality improvement tools to exceed customer expectations and keep them satisfied. If the estimated bias exceeds allowable bias, it is not acceptable.