Between-run precision

The method was validated in accordance to the guidelines of the international conference on harmonization (ICH). Data with respect to accuracy, within- and between run precision, recovery, detection and quantitation limits were reported and found to be within the accepted international criteria. Neither endogeneous substances nor the commonly used dmgs were found to interfere with the retention times of the analytes. Standard solutions of the dmg and quality control preparations at high and low level concentrations were demonstrated to be stable at room temperature and/or -20°C for long and short periods of time. 

In short, there exists a marked and pronounced distinction between a within-run precision (i.e., repeatability) and an in-between-run precision (i.e., reproducibility). 

The precision of this method was evaluated by repeated analysis of the main human faecal BAs (iso-LCA, LCA, iso-DCA, DCA, CDCA, CA, and 12-oxo-DCA). Within-run precision of ten samples amounted to 4-7% for all BAs. The between-run precision was approximately 5-10% of five time-shifted measurements over 1 month of faeces samples. A standard solution of DCA acetate methyl ester with a DCA concentration of 0.875 mg/ml was added to ten faecal samples of the same origin also used for within-run precision. The mean of concentrations amounted to 1.672 mg/ml, corresponding to a recovery of 94.6%. 

Human specimens. In our laboratory, we first developed a good laboratory practice (GLP)-validated procedure for quantification of intact rafAON in control human plasma. The rafAON assay validation endpoints were standard curve, between-run precision and accuracy, within-run precision and accuracy, effects of dilution and freeze thaw, stability of rafAON at -80° C, and 4°C in plasma for various times, specificity, integrity of rafAON during plasma sample collection and processing, and lipid interference. The reader is referred to a previous citation for further details (17,27). 

Precision of an assay describes how well an assay result can be reproduced. Within-run precision is defined as the precision of the same sample run on several occasions with the same assay under the same assay conditions. Between-run precision is an index of the ability of the assay to reproduce the same result on the same sample at different runs, time moments, by different operators or in different labs. Precision is described by the variance (s ), standard deviation (s) and coefficient of variation (CV). 

Precision (as discussed previously) is the ability of the assay to give the same result when repeated multiple times either within the same run, or from day to day (i.e., between runs). Precision data are usually collected early in the evaluation at a new method, since the quality of the method depends on the level of precision. If precision is poor, more elaborate validation experiments must be postponed until the sources of imprecision are identified and controlled. 

Repeatability closeness of agreement between results of successive measurements carried out under the same conditions (i.e., corresponding to within-run precision). Reproducibility closeness of agreement between results of measurements performed under changed conditions of measurements (e.g., time, operators, calibrators, and reagent lots). Two specifications of reproducibility are often used total or between-run precision in the laboratory, often termed intermediate precision and interlaboratory precision (e.g., as observed m external quality assessment schemes [EQAS]) (see Table 14-2). 

Precision. The within-run precision of the assay was determined by assaying three control sera, corresponding to different levels of T4 (mean T4 concentrations of 15, 59.3, and 122 ng/mL), in 12 replicates in a single assay. For the determination of the between-run precision, duplicate measurements of these control sera were performed in 12 different runs. The within-run CVs were 4.5, 5.6, and 4.0% (mean), and the between-run CVs were 5.4, 10.3, and 5.9%, respectively. 

The features to be determined to validate a procedure are repeatability (within-run) and intermediate (between-run) precision, limit of detection, limit of quantification, linearity of the response of the assay, specificity of the assay and whether there are any interferences, its trueness, the vmcertainty associated with an individual result with a stated limit of confidence, and appropriate reference ranges. While examining these topics further information relevant to reagent stability, necessary frequency of recalibration, suitable IQC protocol, and overall assay weakness will be obtained. 

The between-run precision (SD),) measures the variability between various batches of samples analyzed. 

Table 10.3 Example of atable used to record between-run precision and accuracy in analysis of QC samples during validation...

Overall precision (S ) was calculated by combining within-run precision (Sj) and between-run precision... 

A method is required to analyse noise and reproducibility in biomedical vibrational spectroscopy. If spectra are compared at a single wavenumber only, the nomenclature and calculation procedures could readily follow the univariate methods used to evaluate single parameter measurements in standard analytical chemistry. The concepts of precision and bias are frequently introduced in analytical chemistry in order to distinguish between the random noise and the systematic error. While precision evaluates the deviation among repeated measurements and is therefore meant to address the random errors in the quantification of analytes, the bias enumerates the difference between the mean of the average results of repeated measurements and the reference value. Finally, the term accuracy covers both the precision and the bias and it is defined as the closeness of agreement between a test result and the accepted reference value. In analytical chemistry, another frequent distinction is made between the within-run precision ( repeatability ) and the between-run precision ( reproducibility ). These terms are adequate for a univariate comparison of a measured value with a reference value. 

Precision, which is a measure of the variability or dispersion within a set of replicated values or results obtained under the same prescribed conditions, can be assessed in several ways. The spread or range (i.e. the difference between the highest and lowest value) is sometimes used, but the most popular method is to estimate the standard deviation of the data (vide infra). The precision of results obtained within one working session is known as repeatability or within-run precision. The precision of results obtained over a series of working sessions is known as reproducibility or between-runs precision. It is sometimes necessary to separate the contributions made to the overall precision by within-run and... 

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