Besides
imprecision and bias, possible potential sources of uncertainty are observed, including different concentrations of calibrators and reagent in different lots, multiple technologists' involvement and environmental conditions such as humidity and temperature fluctuations.
We created a band of error-transformed values by adding or subtracting the allowable
imprecision to the upper and lower ends of the bias-transformed values and using the most extreme values.
Each of the 12 true glucose concentrations per hour was measured by a simulated glucose assay with a defined
imprecision and bias.
5%, and the maximum analytical
imprecision (CVa) = 0.
In addition to the intermediate
imprecision QC data method above, we also calculated the SDs and z values from the
imprecision data obtained from duplicate analysis of patient samples after exclusion of outliers.
A simulation model that considers bias and
imprecision separately has been used to model the effects of glucose meter error on subcutaneous insulin dose (15).
The results of these computer-simulation studies failed to show any increase in false-positive results between
imprecision values of 10% and 25%.
Y = bias + total
imprecision + random patient interferences (1)
A method for direct estimation of
imprecision profiles, with reference to immunoassay data.
To examine the role of
imprecision on diagnostic accuracy, we obtained data from a multisite clinical trial on the use of the ADVIA Centaur BNP assay (5).
The distribution of values for a cTnI assay, assuming an
imprecision profile with a 25% CV at the 99th percentile limit of 0.
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