Validation Parameters

Question 1

Describes how close a test result is to its true value. Reference samples and standards with known values are needed to check accuracy or comparison of the measured value to the “known value” obtained from a reference material.

Answer 1

VALIDATION PARAMETERS

Question 2

• Usually done by Recovery Study or Method of Comparison
• Use of a reference material → running it as a sample, not a calibrator
• Recovery experiments are conducted if: No comparative method is available
• Used to estimate proportional systematic error proportional systematic error
• Helpful in investigating calibration solutions whose assigned values are used to establish instrument set-points

Answer 2

Accuracy Experiment by Recovery

Question 3

Measure whether a method is able to accurately measure an analyte.

Answer 3

Recovery Studies

Question 4

Performed to determine if specific compounds affect the accuracy of laboratory tests. materials in patient specimens that cause errors which are independent of analyte concentration.
Common interfering substances: Hgb, lipids, bilirubin
Responsible for constant bias

Answer 4

Interference Studies

Question 5

• Affect tests by absorbing or scattering light
• React with the reagent
• Affect the reaction rate used to measure a given analyte

Answer 5

Hgb, lipids, bilirubin

Interference Studies

Question 6

Accuracy Experiment

1. Higher accuracy = lower % bias
2. Increase % recovery = increased accuracy

Answer 6

1. Interference
2. Recovery

Question 7

%recovered formula

Answer 7

% recovered = (measured in spike sample) - (measured in baseline / concentration added x 100

Question 8

Interference formula

Answer 8

concentration w/ interference added divided by conc. w/o interference

Question 9

Formula
Bias =
Bias %

Answer 9

Bias = interference - conc. without interference
Bias % = bias x 100

Question 10

• Comparison to a gold standard
• Run at least 100 samples
• accuracy by method comparison is performed to estimate: inaccuracy or systematic error
• Usually done by: running the same set of specimens in the new method and comparison method
• Remember: It is assumed that the comparative method is correct, thus the error is attributed to the new method

Answer 10

Accuracy by Comparison

Question 11

Accuracy by Comparison

1. If slope (b) is not equal to 1, there is a?
2. If y-intercept (a) is not equal to 0, there is a?
3. If the standard error of the estimate is not equal to 0 then there is a?

Answer 11

1. PSE
2. CSE
3. Random error

Question 12

Accuracy by Comparison

Linear regression analysis (least squares analysis) used to compare two methodologies using the best fit line through the data points.

Answer 12

Deming Regression Analysis

Question 13

Accuracy by Comparison

Graphical representation of the Deming regression analysis

Answer 13

Deming Plot

Question 14

Describes how close the test results are to one another when repeated analysis of the same material is performed

Answer 14

Precision

Question 15

Precision

1. Ability of a test result to be reproduced by several observers working independently
2. Degree of agreement of measurements on replicate specimens by the same observers
3. Types of Imprecision test:

Answer 15

1. Reproducibility
2. Repeatability
3. Total Imprecision & Run Imprecision

Question 16

Precision

1. Measures result variation in a situation where replicated samples are measured under identical conditions
2. Result variation happening between different runs (e.g. between morning and afternoon) of the same measurement setup
3. Result variation happening between days

Answer 16

1. Within run precision
2. Between run precision
3. Between-day

Question 17

Reproducibility Studies for Precision
1. Use what samples?
2. Within run
3. Between-run
4. Calculate:

Answer 17

1. Matrix matched samples
2. Intra-Assay (within-run) Precision > 20x
3. Inter-Assay (between-run) Precision > 20x
4. mean, SD, CV%

Question 18

• To estimate the random error of an analytical method
• To observe the variation expected in a test result under the normal operating conditions of the laboratory.

Answer 18

Precision studies

Question 19

Precision studies

1. Ability of an analytic test to measure a known amount of analyte; a known amount of analyte is added to real sample matrices.
2. Effect of (a) compound(s) on the accuracy of detection of a particular analyte.
3. Substances that cause interference.
4. Body component (e.g., fluid and urine) in which the analyte is to be measured.

Answer 19

1. Recovery studies
2. Interference
3. Interferents
4. Matrix