Assays accuracy

Technology Throughput Cost per assay Accuracy Robustness Operational flexibility... 

Nominal concentration (jUg/ml or pg/g) Intra-assay precision (CV%) ( =10) Intra-assay precision (CV%) (n=6) Intra-assay accuracy (%> ( =10) Intra-assay accuracy (%) ( =6) Recovery (%) (mean SD)... 

Depending on the use of the assay, different parameters will have to be measured during the assay validation. Validation of analytical assays is the process of establishing one or more of the following as appropriate to the type of assay accuracy precision (repeatability, intermediate precision), linearity, range, limit of detection, limit of quantification, specificity, and robustness [1]. For physicochemical methods there are accepted defined limits for these test parameters ... 

The assay precision data is obtained from the 100% level of assay accuracy. (See Sec. 4.1). 

The RSD of the 100%-level assay accuracy values must not be more than 2.0%. 

Assay accuracy or percentage of recovery of the method is represented by a normal distribution centered at 100% and Cp = l (i.e., 6[Pg.411]

Purpose. To evaluate assay accuracy and precision based on the overall performance of analytical QCs as well as STDs. 

Lacking assay accuracy may also stem from the fact, that most LC-MS/MS methods used in clinical laboratories are still locally designed laboratory-developed tests operating on very heterogeneous instrument configurations. Consequently,... 

The calculated intra-assay accuracies ranged from... 

The calculated intra- and inter-assay accuracies ranged from 101-107 %, calculated over all analytes and all three QC levels. 

During analyses of materials containing analytes in markedly different amounts it is necessary to correctly plot curves for relatively narrow concentration ranges. Such multilevel calibration is a way of increasing assay accuracy because the slope of the curve increases with decreasing assayed amounts of the element. 

By using iV as a correction coefficient in an ELISA for the fungicide tetraconazole in fruit extracts [56] or for the insecticide diazinon in surface water samples [58], a considerable improvement in assay accuracy could be attained. A similar constant relationship has been observed between the relative signals given by two spiked analyte concentrations in various matrices (see Eq. (9.12)) ... 

ACCURACY. Assay accuracy was examined by performing a standard addition experiment. To plasma was added either 0, 5 or 10 ng/ml of 13-cis or all trans retinoic acid, followed by extraction (n=10). A mixing experiment (n=4), in which plasma was fortified with both cis and trans retinoic acid, was also performed. No mixing effect was observed. The internal standard was 20 ng/ml throughout. Table II shows the results of this experiment. The observed values correlate quite well for 13-cis retinoic acid. However, the observed values for all trans retinoic acid were less than those calculated. This is most likely due to the somewhat poorer recovery of the all trans isomer from plasma. 

Expected protein mass Assay accuracy averages (%) Average. accuracy (%) Standard error (%) df 95% Confidence interval on accuracy ... 

Case Study 3 Poor Assay Accuracy Data, an Out-of-Specification Investigation 260... 

When the assay accuracy and precision are not satisfactory, it will be necessary to subject the assay procedures to appropriate review, design, study, revision or replacement. 

The recovery of analyte in matrix should be evaluated at a minimum of two concentrations using a sufficient number of replicates (minimum of three). In practice the extraction efficiency is often determined by comparing the mean area response from processed QC samples that are used to determine intra-assay accuracy and precision to the mean area response from recovery samples at each QC concentration. 

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