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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The first replicate on day 1 is 2.

User verification of performance for precision and trueness; approved guideline. 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.

Standards Subsctiption ep5 be the perfect solution. Already Subscribed to this document. No literary matter in The Clinical Biochemist — Reviews is to be reproduced, stored in a retrieval system or transmitted in any form by electronic or mechanical means, photocopying or recording, without permission.

Please first verify your email before subscribing to alerts. The procedures are designed for manufacturers or developers of clinical laboratory measurement methods, and for users of those methods who wish to determine their own performance capabilities or to verify claims from a manufacturer.

Subscription pricing is determined by: The first step is to calculate the s2 of the replicates for each day, then for each result subtract the mean for that day and square the resultant value. Need more than one copy?

Evaluating Assay Precision

Statements of opinion in AACB publications are those of the contributors. These include pooled patient samples, quality control material, or commercial aa2 material with known values.

Selection and analytical evaluation of methods with statistical techniques. The reader is referred to the CLSI documents for details. Support Center Support Center.


Proceed to Checkout Continue Shopping. For the purposes of this example the results of only a single level are shown Table 1. Each level is run in duplicate, with two runs per day over 20 days, and each run separated by a minimum of two hours. R Package Documentation rdrr. As the period of assessment is quite short, the total SD epp05 within-laboratory SD derived from these experiments should not generally be used to define acceptability limits for internal quality control.

Evaluating Assay Precision

CLSI document EPA2 describes the protocols that should be undertaken by the user to verify precision claims by a manufacturer.

While the term precision relates to the concept of variation around a central value, imprecision is actually what is measured. Repeatability Repeatability is estimated using the equation below. For a normal distribution the measure of imprecision is the standard deviation SD. Similarly the within-laboratory precision is estimated by measuring a sample 20 times over multiple days.

Elsevier Saunders; St Louis: Precision claims by a manufacturer should be tested at at-least two levels, by running three replicates over five days.

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It is generally assumed in the laboratory that the variation associated with ep5 analysis will follow a normal distribution, also known as eo05 Laplace-Gaussian or Gaussian distribution. There e05 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.

Finally, we can calculate the total or within-laboratory SD s l using the equation:. NCCLS document EP5-A2, Evaluation of Precision Performance of Quantitative 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. Included are guidelines for the duration, procedures, materials, data summaries, and interpretation techniques that are adaptable for the widest possible range of analytes and device complexity.


This standard is also available to be included in Standards Subscriptions. On day 1 the mean of the three replicates was 1.

The EPA2 protocol is similar except that the experiment is undertaken with three replicates over five days for at least two levels. Unfortunately this approach is insufficient, as it tends to under-estimate repeatability, as the operating conditions in effect at the x2 may not reflect usual operating parameters.

Within-Laboratory Precision Finally, we can calculate the total or within-laboratory SD s l using the equation: For example, on day 1 the average of the three values is 2.

The figure of 5. E;05 one can use the variance, which is simply the square of the SD.

Using the example data and assuming the claimed repeatability is an improbable CV of 1. 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.

Various materials may be used to complete the assessment with either protocol. If this is true then using the principle of analysis of variance components:. 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.