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QC Definitions Flashcards

1
Q

% Error is used when looking for the…

A

Reportable Range

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2
Q

F test - does it measure accuracy or precision?

A

Precision

  • compares 2 data sets
  • small SD (small spread of data)
  • confirm if new test is as accurate as old one
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3
Q

Paired T test - does it measure accuracy or precision? What type of error does it measure?

A

Accuracy

  • compares 2 data sets
  • confirm if new test is as accurate as old one

Systematic Error (SE)

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4
Q

A normal/Gaussian/parametric distribution is when these three values are similar

A

Mean
Median
Mode

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5
Q

How are reference ranges (interval) established?

A

Mean +/- 2SD

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6
Q

How do we find the area under a normal curve at a particular Z score?

A

Look at Z score table

  • area from negative infinity to less than that z score = whatever value the z score is
  • area above z score = 1 - z score value
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7
Q

Proportional Error - affects graphs more at low or high values?

A

High

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8
Q

Constant Error - affects graphs more at low or high values?

A

Low

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9
Q

Define Random Error (RE)

A

Error that cannot be predicted

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10
Q

Define Systematic Error (SE)

A

Constant Error (CE) + Proportional Error (PE)

  • CE = Y-intercept
  • PE = (slope - 1) * 100
  • bias is also a SE (combine effects of CE and PE)
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11
Q

Shifts and trends in a Levey-Jennings chart are what type of error?

A

Systematic Error (SE)

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12
Q

Define Reference Range

A

Expected range of values of an analyte in a healthy population

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13
Q

Factors that contribute to varying Reference Ranges (Reference Range Partitioning Factors)

A

Age, sex, ethnicity, diet, pregnancy, blood type, tabacco use, exercise, geographic location, etc

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14
Q

Another name for Analytical Measurement Range (AMR). Define AMR

A

Reportable Range
Smallest and largest values that can be reported from instrument without dilution
-smallest amount must be distinguishable from blank

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15
Q

When would 20-30 healthy individuals be sufficient for establishing Reference Interval validation? How is the RI verified?

A

Adopt a manufacturer’s existing reference interval

2 or fewer (<10%) values fall outside the proposed limit
-lab must make own RI if rejected

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16
Q

When would 40 healthy individuals be sufficient for establishing Reference Interval validation?

A

Establishing a new Reference Interval with a Gaussian/normal distribution
-for a particular analyte in a population

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17
Q

When would 120 healthy individuals be sufficient for establishing Reference Interval validation?

A

Establishing new Reference Interval with a non-Gaussian/normal distribution

  • discard outliers
  • choose middle 95% of values is the new reference interval
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18
Q

Define Lower Limit of Detection (LLD)

A

Lowest concentration that can be measured

19
Q

Define Biological Limit of Detection (BLD)

A

Lowest concentration that can be measured in the blood

-always higher than LLD (other stuff in blood)

20
Q

Define Functional Sensitivity (FS)

A

Lowest concentration that can be reliably/accurately measured

21
Q

What are good criteria for screening tests?

A

High sensitivity - catch all sick people

Low specificity - catch false positives

22
Q

What are good criteria for confirmatory tests?

A

Good sensitivity - catch all sick people

High specificity - weed out false positives

23
Q

Causes of Systematic Error (SE) (4)

A

New reagent lot number
Wrong or deteriorating reagent
Empty reagent
Incorrect calibration

24
Q

Causes of Random Error (RE) (2)

A

Erratic volume change of sample or reagent (check for loose components)
Temperature changes

25
Pre-analytic process involves... (5)
``` Ordering Identification Collection Transportation Separation -STOIC ```
26
Analytic process involves...
Lab testing | -usually not a source of error
27
Post-analytic process involves... (3)
Reporting Interpreting Action
28
F test vs T test - which one measures if there's significant differences between SDs? Which one measures if there's significant differences between the means?
F test = SD T test = mean
29
What does an r > 0.95 signify? What is another name for r?
Good correlation between the two methods 1.0 is best correlation Correlation coefficient
30
Bias is a measure of what type of error?
``` Systematic Error (SE) -bias is combined effect of both PE and CE ```
31
Diff SD is a measure of what type of error?
Random Error (RE)
32
Define CV. Is a low or high CV better?
Measure of dispersion of data points around the mean Low CV is better = less dispersion CV = (SD/mean) * 100
33
Define false reject and false accept
False reject - QC system shows a flag, but no significant change (12S, 13S) -ideally < 5% of the time False accept - significant change present, but QC system fails to flag it. -very problematic, incorrect results
34
Imprecision, shift, trend - which is associated with SE and which is RE?
SE = shift or trend RE = imprecision -increasing large jumps across large SDs
35
What is the number 1 issue that causes SE?
Wrong or deteriorating reagent
36
Define ANALYTICAL sensitivity and ANALYTICAL specificity. What type of test are they normally associated with?
Analytical sensitivity - lowest concentration of detection -includes LLD, BLD, FS Analytical specificity - things that can interfere with your test Proficiency Testing: CLIA, JCAHO, CAP - high complexity testing
37
When designing an in-house test, what complexity level is it considered?
High complexity
38
Accuracy vs precision experiments
Accuracy - method comparison with gold standard Precision - replication experiment - same unknown - calculate SD, CV - compare controls
39
Reportable Range - ideally, plotting the measured value against the assigned value should give a graph that looks... Should reportable range be smaller or larger than reference interval?
Linear -dilute samples if too concentration Larger - catch patients with really high or low values
40
Linear regression - a perfect slope is at a ___ degree angle
``` 45 degree (slope = 1) slope = 1 means there's no PE ```
41
The Y-intercept is also known as this type of error...
``` Constant Error (CE) -ideally 0 ```
42
The r value is a measure of what type of error?
Random Error (RE)
43
RE and SE - which one is inaccuracy and which one is imprecision?
RE = imprecision SE = inaccuracy

CLS 706 (4 decks)

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