Analytical performance characteristics

Performance Characteristic Method Development Prestudy Validation (Validation Phase) In-Study Validation (Implementation Phase, Sample Analysis Phase) 

Assay reagent selection/stability/ assay format/batch size Identify establish Confirm Monitor, lot changes require confirmation of performance 

Specificity and Selectivity Establish Confirm Confirm in diseased states as available 

Matrix selection/sample preparation/minimum required dilution Establish Confirm, for modified matrices, QCs must be prepared in relevant neat matrix Monitor with changes to lot of matrix, comparability must be demonstrated 

Standard calibrators and standard Select model Confirm Monitor 

As a measuring science, analytical chemistry has to guarantee the quality of its results. Each kind of measurement is objectively affected by uncertainties which can be composed of random scattering and systematic deviations. Therefore, the measured results have to be characterized with regard to their quality, namely both the precision and accuracy and - if relevant - their information content (see Sect. 9.1). Also analytical procedures need characteristics that express their potential power regarding precision, accuracy, sensitivity, selectivity, specificity, robustness, and detection limit. 

Notwithstanding that a large number of definitions exist that have been produced and harmonized by many commissions of international organizations (e.g., IUPAC, IUPAP, ISO, BIPM, IEC, IFCC, OIML), there are still official recommendations and definitions which are not completely satisfying and sometimes confusing (Prichard et al. [2001]). 

In general, it is well-known that analytical results can be assessed and how it is done in detail. On the other hand, an assessment of analytical operations, carried out within the hierarchy of analytical techniques, methods, procedures, and SOPs, takes place scarcely according to standardized viewpoints. 

Excitation Analytical Analytical Analytical Technique Method Procedure 

Standard Operating Procedure (SOP, see ISO 78-2 [1999]). Complete Analytical Procedure, according to Kaiser [1965] 

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Fraser CG, Hyltoft Peterson P (1999) Analytical performance characteristics should be judged against objective quality specifications. CUn Ghem 45 321-322. 

Both in cases (i) and (ii) the experimental uncertainty has to be estimated realistically as is done for the reference value, too. All the sources of variations and deviations have to be included in the calculation of the uncertainty. Efforts of analysts to shine with excellent analytical performance characteristic can have a detrimental effect as the examples in Table 8.1 demonstrate. 

Towards the biosensors with the best analytical performance characteristics... 

Typical analytical performance characteristics that should be considered in the validation of the types of procedures described in this chapter are listed below. Each validation characteristic is defined to ensure consistency in usage of terminology and interpretation ... 

Analytical Performance Characteristics and Interferences in the Different Techniques... 

Methodological approach basehne separation achieved within <10 min. The analytical performance characteristics studied (DL < 100 ng As L for all the species evaluated). The feasibility for the analysis of normal As levels in drinking water was demonstrated. However, it was observed that matrix composition and the sample treatment may affect natural As(in)/As(V) distribution... 

Table 4.4 lists the analytical performance characteristics that need to be confirmed during the prestudy validation phase [4 5,9]. In addition, this table highlights the activities that are needed to progress from method development to help ensure the method will meet the prestudy a priori criteria for method acceptance and for successful acceptance of batch runs (in-study validation). 

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