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Clinical Biochem > QA and QC > Flashcards

QA and QC Flashcards

1
Q

What are pre-analytical errors

A

errors that affect specimens before the tests are performed

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2
Q

What analytes are effected by circadian and diurnal variation

A

electrolytes, glucose, urea, creatinine, uric acid, iron, cholesterol, albumin, total protein, AST, ALT and LD

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3
Q

What variables cause modifiable pre-analytical errors

A

circadian variation, menstrual cycle, fasting, alcohol, smoking, dietary supplements and drugs

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4
Q

What analytes are effected by eating before collection

A

glucose, GH, insulin, ionized calcium, triglycerides, total lipids, iron and LD are made higher

chloride, potassium and phosphate are lowered

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5
Q

What tests are effected by the ingestion of alcohol

A

blood glucose, GGT, lactate concentrations

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6
Q

What tests are effected by smoking tobacco

A

ammonia, blood gases, glucose and immunoglobulins

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7
Q

What is increased when collecting below an intravenous line

A

potassium and glucose

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8
Q

What tests are effected in ambulatory patients

A

albumin, calcium, lipoproteins, cholesterol, thyroxine, ALT, AST, amylase, and immunoglobulins A, G and M

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9
Q

What are the effects of prolonged venous occlusion

A

increased total protein, total lipids, iron, cholesterol, AST, and bilirubin

decreased potassium

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10
Q

What are the effects of fist pumping

A

accumulation of potassium, phosphate, lactate causing decreased blood pH and increased ionized calcium

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11
Q

What effects does hemolysis cause

A

increased LDH, potassium, magnesium, phosphate, asparate aminotransferase, total protein and ammonia

positive interference in cholesterol, triglyceride and creatine kinase assaus

negative interference in bilirubin, albumin and carotene assays

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12
Q

What specimens are photosensitive

A

serum bilirubin, carotene, methotrexate and urine bilirubin, urobilinogen and porphyrin

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13
Q

What specimens are temperature sensitive

A

ammonia, lactate and blood gases

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14
Q

What are delta checks

A

they can detect preanalytical errors comparing current value to previous values

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15
Q

Define accuracy

A

an estimate of non-random systematic error between samples of data. The agreement between the mean estimate of a quantity and its true value

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16
Q

Define central tendency

A

the value about which a population is centred. The mean, median and mode are all used to describe the central tendancy

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17
Q

Define coefficient of variance

A

a statistic that measures the distribution of data about the linear regression line

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18
Q

Define error

A

the difference between a single estimate of a quantity and its true value

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19
Q

Define mean

A

the arithmetic average of a data set

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20
Q

Define median

A

a middle value of the population

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21
Q

Define mode

A

the value of a population that occurs in the greatest frequency

22
Q

Define precision

A

a descriptor of random variation in a population of data

23
Q

Define proportional systematic error

A

an error that is always in one direction, the magnitude of which is a percentage of the concentration of the analyte

24
Q

Define random analytical error

A

an error that cannot be predicted

25
Q

Define standard deviation

A

square root of variance, a measure of imprecision

26
Q

Define systemic analytical error

A

an error that is always in one direction resulting in a loss of accuracy

27
Q

Define variance

A

a statistic used to describe the distribution of data in a population

28
Q

What do random error affect

A

the precision of an assay

29
Q

What do systematic errors affect

A

the accuracy of an assay

30
Q

What is a constant systemic error

A

results are consistently increased or decreased by the same amount regardless of concentration

31
Q

What is a proportional systemic error

A

the analyte is consistently high or low in proportion to the analyte concentration

32
Q

What are desirable properties for QC material

A
  • material available commercially
  • long term stability
  • aliquots or vials available in convenient volumes
  • composed of the same matrix as test
  • contain a known concentration of analyte
    -should have concentration with in normal and abnormal reference ranges
33
Q

What is the standard format for a QC graph

A

levey-jennings chart

34
Q

What is a shift

A

an abrupt and sustained change in control values in a single direction

35
Q

What is a trend

A

a gradual change over time to moving in a single direction

36
Q

What is the 12S rule

A

one control value exceeds the mean +/-2SD
a warning rule

37
Q

What causes a break of the 12S rule

A

random or systematic error

38
Q

What is the 13S rule

A

one control value exceeds the mean +/-3SD
within run

39
Q

What causes a break of the 13S rule

A

random error

40
Q

What is the 22S rule

A

two consecutive controls exceed the same limit by atleast 2SD
within run, across controls
across runs, same controls

41
Q

What causes a break of the 22S rule

A

systematic error

42
Q

What is the R4S rule

A

one observation exceeds the mean plus 2SD and another exceeds the mean minus 2SD
within run, across controls

43
Q

What causes a break of the R4S rule

A

random error

44
Q

What is the 41S rule

A

four consecutive controls exceed the same limit either mean plus 1SD or mean minus 1SD
across runs, same control
across runs, across controls

45
Q

What causes a break of the 41S rule

A

systematic error

46
Q

What is the 10X rule

A

ten consecutive control values fall on one side of the mean
across runs, across controls
across runs, same control

47
Q

What causes a break of the 10X rule

A

systematic errror

48
Q

What are calibrators

A

known concentrations of analytes used to set the relationship between the analyte concentration and detector response

49
Q

When should calibration be performed

A

at least every six months, following replacement of reagents, following major maintenance, when QC demonstrates a shift or trend or is outside of limits

50
Q

What are appropriate calibration materials

A

proficiency testing samples with known results, commercial calibrators, control materials with known results, patient specimens with known results

Clinical Biochem (15 decks)

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