Precision
The degree of agreement among individual test results when the procedure is applied repeatedly to multiple samplings of the same suspension of microorganisms and using different suspensions across the range of the test. Also known as repeatability. (TR33)
The closeness of agreement (degree of scatter) between a series of measurements obtained from multiple sampling of the same homogeneous sample under the prescribed conditions. Precision may be considered at three levels: repeatability, intermediate precision, and reproducibility. It is usually expressed as the variance, standard deviation, or coefficient of variation of a series of measurements. (TR57)
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Specificity
The ability of an analytical procedure to accurately measure or detect a target analyte in the presence of other components in the sample matrix. (TR50) The ability to assess unequivocally the analyte in the presence of components that may be expected to be present. Typically these might include impurities, degradants, matrix, etc. Lack of specificity of an individual analytical procedure may be compensated by other supporting analytical procedure(s). (TR57) The ability to detect a range of microorganisms, which demonstrate that the method is fit for its intended use. (TR33)
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Reproducibility
The precision among multiple laboratories (collaborative studies, usually applied to standardization of methodology). (TR57) The precision between laboratories, for example, through collaborative studies. (TR33)
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Robustness
The measure of capacity to remain unaffected by small, but deliberate, variations in method parameters and provides an indication of its reliability during normal usage. (TR57) (TR33)
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Ruggedness
The degree of intermediate precision or reproducibility of test results obtained by assessing the same samples under a variety of normal test conditions. (TR33)
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Limit of Quantification
The lowest number of microorganisms in a test sample that can be enumerated with acceptable accuracy and precision under the stated experimental conditions. (TR33)
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Limit of Detection (LOD)
The lowest concentration of microorganisms in a test sample that can be detected, but not necessarily quantified, under the stated experimental conditions. (TR33) The lowest amount of analyte in a sample that can be distinguished from the absence of analyte. (TR41) The lowest concentration of analyte that can be unambiguously detected in a sample. For qualitative and for quantitative NAT methods, this value is conventionally expressed as a 95% positive cut-off value, representing the target concentration detected in 95% of repeated tests using a certain assay. (TR50)
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Linearity
The ability to elicit results that are proportional to the concentration of microorganisms present in the sample within a given range, where accuracy and precision are demonstrated. (TR33) The linearity of an analytical procedure is its ability (within a given range) to obtain test results that are directly proportional to the concentration (amount) of analyte in the sample. (TR57)
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Intermediate Precision
The precision within the same laboratory using different analysts, equipment, reagents and/or on different days. (TR33)
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Inclusivity
The ability of an assay to detect a target microorganism. (TR33)
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False Positive
A test result that is erroneously classified in a positive category (e.g., a viable microbial detection result when viable microorganisms are not present). (TR33)
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False Negative
A test result that is erroneously classified in a negative category (e.g., the absence of a viable microbial detection result when viable microorganisms are present). (TR33)
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Exclusivity
The capacity of an assay not to detect microorganisms closely related to a target microorganism. (TR33)
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Equivalence/Comparative Testing
A measure of how similar the test results are when compared with the existing method. (TR33)
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Alternative or Rapid Microbiological Method (RMM)
A novel, modern and/or fast microbiological testing method that is different from a classical or traditional growth-based method, such as agar-plate counting or recovery in liquid broth media. The alternative or rapid method may utilize instrumentation and software to manage the testing and resulting data, and may provide quantitative, qualitative and/or microbial identification test results. Automated technologies that utilize classical growth-based methods may also be designated as being novel, modern or rapid, based on their scientific principle and approach to microbial detection. The terms alternative, rapid microbiological method, rapid method and the acronym RMM are used interchangeably within this technical report. (TR33)
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Accuracy
The closeness of the actual test results obtained by the new method to the actual test results obtained by the existing method. (TR33) An analytical procedure expresses the closeness of agreement between the value that is accepted either as a conventional true value or an accepted reference value and the value found. This is sometimes termed trueness. (TR57)
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