MIDTERMS: L1 - QC AND QA Flashcards
Laboratory’s best estimate of the analyte’s true value for a specific level of control.
MEAN
Quantifies how close numerical values are in relation to each other.
STANDARD DEVIATION
Note: SD is used to set up limits
MOTF
1 . Low SD - implies that the data values are spread out over a large range of values
2. High SD - implies that the data values/points are very close to the mean
Both False
High SD - implies that the data values are spread out over a large range of values
Low SD - implies that the data values/points are very close to the mean
Described as a graph of all the quality control results in a month
LEVEY JENNINGS CHART
Note: minimum of 20 controls
A measure of variability
Coefficient of Variation
Useful for comparison
of precision for two different methods or instruments
Coefficient of variation
It can also be used as a part of the Internal Quality Control system when performing patients precision testing
Coefficient of variation
Note: The lower the CV, the better
MOTF
SDI (Standard Deviation Index)
1. A statistic that measures your lab’s bias relative to your consensus group.
2. It is an estimate of reliability
3. SDI is useful in testing accuracy of a method
All are True
SDI (Standard Deviation Index)
interpretation of results:
0 - Ideal score; identical to your peer group
(+/-) 1 to 1.5 - Acceptable to marginal performance; may need to investigate test system bias
(+/-) 1.5 to 2.0 - Marginal performance; may need to perform corrective action
A statistic that compares your lab’s precision to that of other labs in a consensus group
CRV (Coefficient of Variation Ratio)
Note: Consensus group is still present but in this case, for your CVR, the inter-laboratory group CV is used not the reference method
CRV (Coefficient of Variation Ratio) results and interpretation:
Less than 1 - Acceptable performance; indicates that precision is better than the peer group
1 to 1.5 - Acceptable to marginal performance; may need to investigate test system imprecision
1.5 to 2.0 - Marginal performance; may need to perform corrective action
MOTF
1. Shift - defined as abrupt changes in the control values
2. Shifts in QC data represent a sudden and dramatic
positive or negative charge in test system performance
3. 4 or more consecutive results fall on one side of the mean means there is a shift
1,2- true
3 - false
3 - must be 6 or more = REJECT
- Indicates a gradual loss of reliability in the test system (6 values)
- Usually subtle
Trent
MOTF
1. Systematic Error - a trend or shift away from the laboratory mean
2. Systematic Error - can still be acceptable
3. Random error - any random deviation away from the laboratory
mean
4. Reject if the data value that shows the random
error exceeds ± 2SD
Only 2 is incorrect
2 - not acceptable
T or F
One control - values are said to be in control if they fall
within the ± 2SD
True
A “multi-rule” system developed by Dr. James O. Westgard based on statistical concepts
Westgard Multirule System
MOTF
Westgard Multirule System
1. Use 1-2 or more controls
2. a combination of decision criteria or rules to assess if a system is in-control
1 false, 2 true
1 - need atleast 2 levels of control
When a single control observation is outside the ± 2s limits.
12s rule
12s rule
- Not a reason for rejection
- Warning rule
Both true
MOTF
22s rule
1. Violation indicates random error that occurs outside the +/- 2SD
2. Two consecutive controls exceed the mean by +/- 2SD
1 false, 2 true
1 - systematic error
41s Rule
- 4 consecutive controls on one side of the mean exceeds
+/-1SD
- Systematic error
True
10 consecutive controls on one side of the mean, systematic error
10x rule
There is only one data value that occurs outside the ± 3SD, random error
13s rule
f there is at least a 4s difference between control values within a single run, the rule is violate for random error
R4s Rule
MOTF
- BIAS/SDI RESULTS ACCURACY /RELIABILITY ARE AFFECTED - very far values from each other
- PRECISION/REPEATABILITY/CV/ CVI ARE AFFECTED - fall only on one side of the mean
Both false
