Quality Assessment Flashcards
System of ensuring precision and accuracy, it is q system of technique to ensure with a specified degrees of confidence
Quality control
Overall program , more process oriented
Quality assurance
Laboratory workflow
Pre analytical phase
Analytical phase
Post analytical phase
Parameters of quality control
Sensitivity
Specificity
The ability of a method to detect and measure even the smallest amount of the particular substance tested for
Sensitivity
Measure minute concentration of the analyte
Analytical sensitivity
Test must always give a positive result in the presence of the disease
Diagnostic sensitivity
The ability of a method to measure only the component desired without interference of some substances
Specificity
Measure only one unknown substance
Analytical specificity
Must always give a negative result in the absence of disease
Diagnostic specificity
Positive result that also have disease
True positive
Negative test result and do not have disease
True negative
Positive test result but do not have disease
False positive
Negative test result but have the disease
False negative
Exact value of the substance of interest in the sample
It is the closeness or the nearness of a test value to the original value
Accuracy
Give repeated results on the same sample that agrees with one another.
Precision
Ability of method to have the same results
Reproducibility
Degree by which a method is easily repeated with less effort
Practicality
When to perform quality control
Beginning of each shift
New instrument
After an instrument is serviced
When reagent lots are changed
After calibration
Whenever patient results seem inappropriate
Purposes of quality control
To check the stability of machine
To check the quality of reagents
To check for technical or clerical error if any was committed by the operator
- For accuracy
- a solution of known characteristics and known value
- one known constituent only and used as a basis of reference
- 100% pure
Standard solution
- for precision
- a solution composed of several known constituents which can be run simultaneously
- liquid or lyophilized
- stable for a long period of time
Control solution
-Solution without specimens
- It sets the spectrophotometer reading to zero.
- distilled water as reagent blank vs specific reagent
Blank solution
Type of error which varies from sample to sample, variation in technique
Random error
Cause of random error:
Mislabeling a sample
Improper mixing of sample
Pipetting error
Type of error that influences observations consistently in one direction, constant difference
Systematic error
Cause of systematic error
Deterioration of reagents
Sample instability
Highest frequency of this type of error occurs with the use of handwritten labels and request form
Clerical error
It is the measure of central tendency
Mean
It is the measure of spread of data, describe the normal curve, measure of the distribution range
Standard Deviation
It is the percentile expression of the mean, an index of precision
Coefficient of variation
Statement of variability and measures the significant differences between groups of data
Variance
It demonstrates acceptable limits of variation in the result of an analytical method
Shewart- Levey Jennings Chart
It occurs when data elements are centered around the mean with the most elements close to the mean
Gaussian Curve
Plotted with the accumulated differences between QC results and the target means
Cumulative Sum graph
It is used to compare results obtained on a high and low control serum from different laboratories
Youden plot
When the values of the control fall within the confidence limit
In control
When the values of the control fall outside the confidence limit
Out of control
Types of error in control charts
Trend
Shift
Outliers
Formed by controlled values that is either increase or decrease for at least 6 consecutive days
Trend
Formed by controlled values that distribute themselves on one side of the mean for at least 6 consecutive days
Shift
These are control values that are far from the main set of values
Outliers
Types of quality control program
Internal quality program
Enternal quality program
Analysis or comparison of in-house controls and patient samples
Internal QC
For proficiency testing
External QC
