les 7 Flashcards
Standard deviation squared. Assuming all sources
of error are independent of each other, total error is the sum of variances of individual sources of error
Variance
A statistic that describes the amount of
variance of a set of measurements about the mean value. It is
used to describe the random error of an analytical method
- Standard deviation
The interval between the beginning of one
event to the end of another event in the total testing process. Typically measured as the collection to reporting time or as the receipt of specimen in laboratory to reporting
time.
- Turnaround time
Part of specimen that is measured.
Material of known or assigned concentration used for assay calibration.
Standard
The lowest detection limit of an assay;
sometimes measured as the concentration of an analyte that can
be differentiated from a blank within a 95% confidence interval
Sensitivity, analytical
The ability of an analytical method to
determine solely the component(s) it purports to measure.
- Specificity, analytical
Test results that are within expected
parameters for about 95% of all individuals in a defined
healthy population. Values outside of the range are classified
as abnormal and may be associated with a pathological
condition
Amount (usually expressed as percentage) of
known quantity of an analyte that is measured when added
to a specimen
Recovery
A variance from expected that is not
reproducible or predictable
- Random error
A process for monitoring assay performance
to detect deviations from expected outcomes
Quality control
A systematic approach to continuously
analyzing, improving, and reexamining the total testing
process
Quality assurance
Quality control limits derived from
clinical application of results rather than statistical
imprecision of the method
Medical usefulness limits
An error that is always in one
direction and whose magnitude is a percentage of the concentration of analyte being measured
Proportional systematic error
Arithmetic average of a set of values.
Mean
See reference range
- Normal range
Amount of error associated with an
analytical method that can be tolerated without invalidating the medical usefulness of the result.
Maximum allowable error (MAE)
total constituents of the specimen that may affect the analytical process
Matrix
One or more specimen constituents that cause bias by affecting the analytical method.
Interference
Analytical variance, usually expressed as the standard deviation or coefficient of variation ([standard deviation/ mean] ×100).
Imprecision
Rule-based method to compare a patient’s
current test result to a previous measurement to check for
unexpected differences that might be due to analytical or
nonanalytical errors in the testing process
Delta check
A random distribution of values de- scribed by
their average and variance (standard deviation); used to describe analytical imprecision.
- Gaussian distribution
Deviation of measured concentration from expected or
true value
Error
Specimen that is repeatedly analyzed, with
test results statistically analyzed to monitor method
performance
Control material
An error that is always in the
same direction and of the same magnitude, even as the
concentration of analyte changes.
Constant systematic error
Expected range of values within a group
with a specified probability.
- Confidence interval
A range of expected values that, if exceeded,
warns of random and/or systematic error in an analytical
process
Control limit
A measure of variance expressed as
a percentage of the mean ([standard deviation/mean] ×100).
Coefficient of variation
Process of using standards of known
concentration to establish a relationship between the measured signal from the instrument and analyte concentration.
Calibration
Systematic error that describes the difference between measured and true or assigned value.
Bias
The range of concentration or other quantity in the
specimen over which the method is applicable without modification.
Analytical range
Set of written instructions that describe the
procedure, materials, and equipment necessary for the analyst to
obtain a result.
Analytical method
The difference between the result of an analytical
method and the true value.
Analytical error
Sample to be measured
Analyte
Agreement between the best estimate of a quantity and its
true value.
Accuracy
