The determination of accuracy indicates how close the measured concentration is to the true or nominal concentration (see Table 1). This step assesses the systematic error or bias of the entire analytical procedure (analyte extraction, reconstitution, analysis). Known amounts of analyte are added to the matrix and measured. A minimum of three concentrations that span the standard curve should be assessed, and at least five determinations or replicates should be conducted for each concentration. Accuracy is

TABLE 1 Intra- and Between-Run Accuracy and Precision of Drug X

Nominal drug concentration (ng/mL)

Intra-run Mean

Accuracy (%) Precision (% CV) Between-run Mean S.D.

96 110 94 98 97

84 89 86 87 93

calculated as

7 Accuracy — 11 (nominal concentration — measured concentration) | ^

The acceptance criteria for accuracy is ±15% of the nominal concentration, but at the LLOQ an error of ±20% is permissible.

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