QUALITY ASSURANCE and QUALITY CONTROL
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Process by which lab ensures quality results by closely monitoring preanalytical, analytical, & post analytical stages of testing
QUALITY ASSURANCE
Examples of Preanalytical phase; everything that precedes test performance:
• Test ordering • Patient preparation • Patient ID • Specimen collection • Specimen transport • Specimen processing
Examples of Analytical phase; everything related to assay:
• Test analysis • Quality control (QC) • Reagents • Calibration • Preventive maintenance (involves machines)
Examples of Postanalytical phase; everything that comes after test analysis:
• Verification of calculations & preference ranges • Review of results • Notification of critical values • Result reporting • Test interpretation by physician • Follow-up patient care • Delta check
Part of analytical phase of quality assurance; process of monitoring results from control samples to verify accuracy of patient results
Quality Control (QC)
It is the average of data points:
Mean
It is the midpoint of distribution
Median
It is the most frequent observation
Mode
It is the difference between highest and lowest value; easiest measure of spread
Range
Most frequently used measure if variation:
Standard Deviation (SD)
An index of precision used to compare the dispersion of two or more groups of data with different units/concentrations
Coefficient of variation (CV)
Used to determine if there is a significant difference between the means of two groups of data; compares accuracy
T-test mnemonic: “ATM” A - Accuracy T - T-test M - Mean
Used to determine if there is a significant difference between the SD of two groups of data; compares precision:
F-test mnemonic: “SPF” S - SD P - Precision F - F-test
____% of the data fall between 1+/- SD from the mean
68%
_____% of the data fall between +/-2 SDs from the mean.
95%
_____% of the data fall between +/-3 SDs from the mean
99%
Relationship of SD with Dispersion:
Directly proportional
Relationship of SD with Precision:
Inversely proportional
Nearness or closeness of assayed values to the true value:
Accuracy
Nearness or closeness of assayed valued to each other
Precision (Reproducibility)
Ability of an analytical method to maintain accuracy and precision over an extended period of time
Reliability
Degree by which a method can easily be repeated
Practicability
Ability to measure the smallest concentration of the analyte of interest
Analytical sensitivity
Ability to measure only the analyte of interest
Analytical specificity