QA and QC Flashcards
What are pre-analytical errors
errors that affect specimens before the tests are performed
What analytes are effected by circadian and diurnal variation
electrolytes, glucose, urea, creatinine, uric acid, iron, cholesterol, albumin, total protein, AST, ALT and LD
What variables cause modifiable pre-analytical errors
circadian variation, menstrual cycle, fasting, alcohol, smoking, dietary supplements and drugs
What analytes are effected by eating before collection
glucose, GH, insulin, ionized calcium, triglycerides, total lipids, iron and LD are made higher
chloride, potassium and phosphate are lowered
What tests are effected by the ingestion of alcohol
blood glucose, GGT, lactate concentrations
What tests are effected by smoking tobacco
ammonia, blood gases, glucose and immunoglobulins
What is increased when collecting below an intravenous line
potassium and glucose
What tests are effected in ambulatory patients
albumin, calcium, lipoproteins, cholesterol, thyroxine, ALT, AST, amylase, and immunoglobulins A, G and M
What are the effects of prolonged venous occlusion
increased total protein, total lipids, iron, cholesterol, AST, and bilirubin
decreased potassium
What are the effects of fist pumping
accumulation of potassium, phosphate, lactate causing decreased blood pH and increased ionized calcium
What effects does hemolysis cause
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
What specimens are photosensitive
serum bilirubin, carotene, methotrexate and urine bilirubin, urobilinogen and porphyrin
What specimens are temperature sensitive
ammonia, lactate and blood gases
What are delta checks
they can detect preanalytical errors comparing current value to previous values
Define accuracy
an estimate of non-random systematic error between samples of data. The agreement between the mean estimate of a quantity and its true value
Define central tendency
the value about which a population is centred. The mean, median and mode are all used to describe the central tendancy
Define coefficient of variance
a statistic that measures the distribution of data about the linear regression line
Define error
the difference between a single estimate of a quantity and its true value
Define mean
the arithmetic average of a data set
Define median
a middle value of the population
Define mode
the value of a population that occurs in the greatest frequency
Define precision
a descriptor of random variation in a population of data
Define proportional systematic error
an error that is always in one direction, the magnitude of which is a percentage of the concentration of the analyte
Define random analytical error
an error that cannot be predicted
Define standard deviation
square root of variance, a measure of imprecision
Define systemic analytical error
an error that is always in one direction resulting in a loss of accuracy
Define variance
a statistic used to describe the distribution of data in a population
What do random error affect
the precision of an assay
What do systematic errors affect
the accuracy of an assay
What is a constant systemic error
results are consistently increased or decreased by the same amount regardless of concentration
What is a proportional systemic error
the analyte is consistently high or low in proportion to the analyte concentration
What are desirable properties for QC material
- 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
What is the standard format for a QC graph
levey-jennings chart
What is a shift
an abrupt and sustained change in control values in a single direction
What is a trend
a gradual change over time to moving in a single direction
What is the 12S rule
one control value exceeds the mean +/-2SD
a warning rule
What causes a break of the 12S rule
random or systematic error
What is the 13S rule
one control value exceeds the mean +/-3SD
within run
What causes a break of the 13S rule
random error
What is the 22S rule
two consecutive controls exceed the same limit by atleast 2SD
within run, across controls
across runs, same controls
What causes a break of the 22S rule
systematic error
What is the R4S rule
one observation exceeds the mean plus 2SD and another exceeds the mean minus 2SD
within run, across controls
What causes a break of the R4S rule
random error
What is the 41S rule
four consecutive controls exceed the same limit either mean plus 1SD or mean minus 1SD
across runs, same control
across runs, across controls
What causes a break of the 41S rule
systematic error
What is the 10X rule
ten consecutive control values fall on one side of the mean
across runs, across controls
across runs, same control
What causes a break of the 10X rule
systematic errror
What are calibrators
known concentrations of analytes used to set the relationship between the analyte concentration and detector response
When should calibration be performed
at least every six months, following replacement of reagents, following major maintenance, when QC demonstrates a shift or trend or is outside of limits
What are appropriate calibration materials
proficiency testing samples with known results, commercial calibrators, control materials with known results, patient specimens with known results
