QUALITY CONTROL Flashcards
Is a system of ensuring accuracy & precision in the laboratory by including quality control reagents in every series of measurements
Quality Control
is a systematic action necessary to provide adequate confidence that laboratory services will satisfy the given medical needs for patient care
Quality Assurance
material of known concentration used in developing a standard curve and/or instrument calibration
Standard
sample of known quantity with several analytes present
Control
2 Types of Quality Control
- Interlab QC
2. Intralab QC
2 Levels of control solutions in General Chemistry
- Pathologic
2. Non-Pathologic
QC done within the Laboratory
Intralab Quality Control
Maintaining long term quality control
Involves proficiency testing programs that periodically provide samples of unknown concentrations to participating clinical laboratories
Determine state-of-the-art of the analytical methods
Interlab quality control
Internal QC
Intralab Quality Control
External QC
Interlab quality control
Gold standard for clinical laboratory external QC testing
College of American Pathologists (CAP)
Intralab QC Is done every ______
Everyday
Immuno Assays QC Level
- Low QC
- Normal QC
- HIgh QC
Ability of an analytical method to measure the smallest concentration
Sensitivity
Is the Ability of an analytical method to measure ONLY the analyte of Interest
Specificty
Is the Nearness or Closeness of the Assayed value to the true or target value
Accuracy
The ability of an analytical method to give repeated results on the same sample that agree with one another
Precision
The degree by w/c a method is easily repeated.
Practicability
The ability of an analytical method to maintain accuracy & precision over an extended period of time during w/c equipment, reagents, & personnel may change
Reliability
Other name for precision
Reproducibility
The Ability of an analytical method to detect the proportion of individuals with the disease. (Screening tests require high sensitivity)
Diagnostic Sensitivity
The Ability of an analytical method to detect the proportion of individuals without the disease. (Confirmatory tests require high specificity)
Diagnostic Specificity
highest frequency occurs with the use of handwritten labels and request forms
Clerical Error
Random Error Vs. Systematic Error
Random Error>Varies from sample to sample
>Present in all measurement
>Due to chance
Systematic Error> Error that influences observations consistently in one directions
Example of random error
> Pipetting error
Mislabeling of samples
Temperature fluctuations
Improper mixing of sample and reagent
Example of Systematic error
>Calibration problems >Deterioration of reagents and control materials >Improper made of standard solutions >Contaminated Solutions >Unstable and inadequate reagent blanks
measure of central tendency; measure of accuracy; AVERAGE
Mean
measure of dispersion of values from the mean; measure of precision; most frequently used measure of variation
Standard deviation
index of precision; percentile expression of the mean
Coefficient variation
measure of variability
Variance
determines whether there is a statistically significant difference between the standard
deviations of two groups of data
F-Test
determines whether there is a
statistically significant difference between the means of
two groups of data
T-Test
MIDPOINT of the distribution;
value of the observation that divides the observation into
two equal groups of data
Median
most FREQUENT observation
Mode
is the difference between the
highest and lowest score in data
Range
data element are centered around the mean with most elements close to the mean
Gaussian Curve
provides the earliest
indication of systematic error (trend); requires computer
implementation
Cumulative Sum Graph
compare results obtained on
a high and low control serum from different laboratories
Youden/Twin Plot
most widely used QC chart in the clinical laboratory; allows laboratorians to apply multiple rules without the aid of computer;
identifies both random and systematic error
Shewhart Levey-Jennings Chart
Trend Vs. Shift
TREND>Main cause: deterioration of reagents
>Control values either increase or decrease for six consecutive days
SHIFT> Main caused:Improper calibration
> Control values that distribute themselves on one side or either side of the mean for six consecutive days
Westgard Rule Random Error
12s
1 3s
R 4s
Westgard rule Systematic errors
2 2s
4 1s
10x rule
1 control value exceeds +/- 2SD; rejection or warning rule
1 2s
1 control value exceeds +/- 3SD
1 3s
Range/difference etween the highest and lowest control result within an analytical run is 4SD
R 4s
2 consecutive control values exceed either +/-2SD
2 2s
4 consecutive control values exceed +/-1SD
4 1s
10 consecutive control values fall on 1 side or the other side of the mean
10x Rule
Interlab qc proficiency testing is done every______
6 months
