EP5-A2. ISBN Volume 24 Number ISSN Evaluation of Precision Performance of Quantitative Measurement. Methods; Approved. Evaluation of Precision Performance of Quantitative Measurement Methods; Approved Guideline, EP05A2E. Clinical and Laboratory Standards Institute (CLSI) document EPA2 describes the protocols for determining the precision of a method. The precision of a.

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In order to compare the estimated repeatability to a claimed value we can calculate the critical or verification value using the equation:. 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.

Description Usage Format References. Reproducibility is at the other extreme and refers to the closeness of agreement between results of successive measurements obtained under changed conditions time, operators, calibrators, reagents, and laboratory.

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.

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Finally, we can calculate the total or within-laboratory SD s l using the equation:. For this, longer-term assessment is required.

Each level is run in duplicate, with two runs per day over 20 days, and each run separated by a minimum of two hours. Alternatively one can use the variance, which is simply the square of the SD.


Evaluating Assay Precision

NCCLS document EP5-A2, Evaluation of Precision Performance of E;05 Measurement Methods; Approved Guideline – Second Edition provides guidance and procedures for evaluating the precision of in vitro diagnostic devices and includes recommendations for manufacturers in evaluating their devices and methods when establishing performance claims. Table 3 shows the results of the same calculation for the remaining days.

Subscription pricing is determined by: Open in a separate window. If the repeatability and within-laboratory SD are less than that indicated by the manufacturer, then the user has demonstrated precision consistent with the claim and no further calculations are required.

As alluded to above, EPA2 is generally used a22 verify that a method is performing as is claimed by the manufacturer. Precision claims by a manufacturer should be tested at at-least two levels, by running three replicates over five days. Standards Subscriptions from ANSI provides a money-saving, multi-user solution for accessing standards. Variance Component Analysis Description Usage Format References Description This data set consists of simulated measurements for an experiment conducted to evaluate the precision performance of measurement methods.

Evaluating Assay Precision

2a What can we improve? Dr Douglas Chesher e-mail: Unfortunately this approach is insufficient, as it tends to under-estimate repeatability, as the operating conditions in effect at the time may not reflect usual operating parameters.

EPA2 should be used to validate a method against user requirements, and is generally used by reagent and instrument suppliers to demonstrate the precision of their methods. Clinical and Laboratory Standards Institute.

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.


These include pooled patient samples, quality control material, or commercial standard material with known values. Care must be taken in knowing which term is being referred to. Marginal Effects for Model Objects. Thus, factor ‘day’ is the top-level random factor variance componentfactor ‘run’ is nested within ‘day’. When undertaking the assessment the data must be assessed for outliers, which are considered to be present if the absolute difference between replicates exceeds 5.

Introduction Part of the process of verifying or validating a method to confirm that it is suitable for use is an assessment of precision. The figure of 5. Summary When evaluating the wp05 of a method it is necessary to assess dp05 repeatability within-run and the total or within-laboratory precision.

Summing the square of the differences gives a total of 0. On 20 days two separate runs with two replicates of the same sample are measured. The page or its content looks wrong.

If an outlier is found the pair should be rejected and the cause investigated and resolved before repeating the run. For the purposes of this discussion reproducibility will not be considered, as it involves multiple laboratories.

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