Statistics and QC Flashcards
The conformance to the requirements of users or customers
quality
includes all systematic actions planned and implemented to provide adequate confidence that test results and services satisfy the needs of the patient
quality assurance
This includes the analytical phase of testing
quality control
defined as all procedures inside and outside the laboratory that precede the test process
pre-analytical quality assurance
defined as all processes performed at the instrument to assure correct test results
analytical quality assurance
defined as all processes performed after the laboratory report leaves the laboratory
post-analytical quality assurance
Factors include: correct ordering of tests, preparation of the patient, correct patient ID, proper collection of the sample, timely transport to the lab, proper handling from collection to analysis, and proper handling within the laboratory
pre-analytical quality assurance factors
Factors include: use of internal and external QC programs, use of monitor sheets requiring written verification of completeness, proper labeling and use of reagents, preventative maintenance procedures for the instruments, documentation of temps for refrigerators/heat blocks, accuracy checks for balances and thermometers, current procedure manuals, and current safety procedures
Analytical quality assurance factors
Factors include: reference range selection, documentation of clerical errors, timely reporting of results, verification of calculations on final reports, a review process of final results for transcription errors, verification of a user friendly report, timely turnaround time, correct result interpretation by the caregiver, and assurance that lab tests results in appropriate patient care
post-analytical quality assurance factors
These are used to monitor the precision and accuracy of a method; used to validate whether the instrument or method is reliable, therefore patient results are also reliable; include a range of numbers
controls
these are used in the analytical process to standardize the method or instrument; has an exact amount or one given value
standards
these are determined by dissolving a weighed amount of standard material in an appropriate solvent and diluting to a stated volume or mass
primary calibration standard
this is what standard we use in the lab where the concentration or other quantity is determined by an analytical method of stated reliability. Standard is prepared, then analyzed to determine the value of the standard, and then purchased by our lab.
secondary standard
What are the three general guidelines NCCLS provides concerning concentrations and number of control materials to test per day?
1 the number and conc. should be sufficient to cover the range of interest
2 a minimum of two concentration levels of controls is recommended and chosen to correspond to clinical decision levels if possible
3 the control levels chosen should reflect values seen in patient specimens in the lab
What are 8 desirable features of quality control materials?
1 analyte conc. at medically significant levels
2 control matrix as much like the human specimen as possible
3 control material stability of 1 year if possible for unopened material
4 stability after opening or reconstitution
5 low vial to vial variation
6 available in large batches
7 material is ready to use or requires minimal preparation
8 material is reasonably priced
this is a control which has been prepared or purchased with a stated or expected value; used with a small number of tests; expensive
assayed control
this is a control whose value is not known except when assayed within the laboratory by repeated testing; used for a large quantity of tests in a large lab; less expensive
unassayed controls
the spread or dispersion of values studied
distribution
illustrates dispersion graphically displayed as XY plots, bar graphs, or histograms
distribution curve
this is represented by a “bell-shaped” curve or a symmetrical spread of data about a central location
normal distribution
limits between which a specified proportion of a population is expected to lie with respect to a measured characteristic
confidence limits
refers to the odds that a value equal to or larger than the one obtained would occur by chance alone
probability
What is the percentage of observations expected to lie within one SD?
68.2%
What is the percentage of observations expected to lie within two SD?
95.5%
What is the percentage of observations expected to lie within three SD?
99.7%
What is the confidence limit used in the clinical lab?
95.5%
the arithmetic average value calculated as the sum of all individual values divided by the number of observations; it is an indicator of central tendency and is therefore related to accuracy or systematic error
mean
the value found at the center of all the observations, with an equal number of observations above and below it
median
the value in the sample or population which occurs with the greatest frequency
mode
the difference or spread between the highest and lowest values or observations in the sample; provides the simplest definition of dispersion
range
the square root of the average squared deviation from the mean; measures spread or distribution of a group of data around the mean; measures the width of distribution and is related to imprecision or random error
standard deviation
a measure of the variability about the mean or SD^2
variance
the standard deviation expressed as a percentage of the mean; (SD/mean) x 100
coefficient of variation (CV)
What are two uses of calculating SD?
1 measures spread or distribution of a group of data around the mean
2 measures the width of the distribution and is related to imprecision or random error
What 3 statistics describe central tendency?
mean, median, and mode
What 3 statistics describe variability about the mean?
range, standard deviation, and variance
Includes pre-analytical, analytical, and post-analytical factors, such as verification of sample collection quality, sample processing procedures, test method selection, reporting of results, and interpretation of the final report.
quality assurance
Includes pre-analytical, analytical, and post-analytical factors, such as verification of sample collection quality, sample processing procedures, test method selection, reporting of results, and interpretation of the final report.
quality assurance
