QA & QC Chapter

Question 1

Accuracy

Answer 1

The closeness of agreement of a measured value with the true value

Question 2

Average

Answer 2

The sum of a set of values divided by the number of values in the set; aka the mean

Question 3

Blind spot

Answer 3

An assayed sample that is provided as an unknown to laboratories participating in proficiency testing programs

Question 4

Calibration

Answer 4

The process of checking, standardizing, or adjusting a method or instrument so it yields accurate results

Question 5

Coefficient of variation

Answer 5

Aka CV - a calculated value that compares the relative variability between different sets of data

Question 6

Controls

Answer 6

Commercially available assayed solutions that are chemically and physically similar to the unknown and are tested in the same manner as the unknown to monitor the precision of a test method.

Question 7

Gaussian curve

Answer 7

A graph plotting the distribution of values around the mean normal frequency curve

Question 8

Levey- Jennings chart

Answer 8

A quality control chart used to record daily quality control values.

Question 9

Mean

Answer 9

The sum of a set of values divided by the number of values in the set; the average

Question 10

Population

Answer 10

The entire group of items or individuals from which the samples under consideration are presumed to have come

Question 11

Precision

Answer 11

Reproducibility of results: the closeness of obtained values to each other.

Question 12

QA

Answer 12

Quality assessment - in the laboratory a program that monitors the total testing process with the aim of providing the highest quality patient care. Formally called quality assurance.

Question 13

QC

Answer 13

Quality control - a system that verifies the reliability of analytical test results through the use of standards, control, and statistical analysis.

Question 14

QS

Answer 14

Quality System - in an institution, a comprehensive program in which all areas of operation are monitored to ensure quality with the aim of providing the highest quality patient care.

Question 15

Random error

Answer 15

Error that is inconsistent and whose source cannot be definitely identified

Question 16

Sample

Answer 16

In statics a subgroup of a population

Question 17

Shift

Answer 17

An abrupt change from the established mean indicated by the occurrence of all control values on one side of the mean

Question 18

Standard

Answer 18

A chemical solution of a known concentration that can be used as a reference or calibration substance

Question 19

Standard deviation (s)

Answer 19

A measure of the spread of a population of values around the mean

Question 20

Statistics

Answer 20

The branch of mathematics that deals the collection, classification, analysis, and interpretation of numerical data, a collection of quantitative data

Question 21

Systematic error

Answer 21

Error that is introduced into a test system and is not a random occurrence.

Question 22

Trend

Answer 22

An indication of error in the analysis, detected by a progressive drift of control values in one direction for at least 5 consecutive runs.

Question 23

Variance ( s^2)

Answer 23

The square of the standard deviation, mean square deviation

Question 24

Westgard rules

Answer 24

A set of rules used to determine when a method is out of control.

Question 25

What are westgard rules? And what does it mean if rules are failed

Answer 25

If rules are not met, means the test results are rejected. Can not report until method is considered “ in control “ - both controls are outside the +/- 2s limit - the same control level ( concentration) is outside the +/- 2s limit in two successive runs. - controls in four consecutive runs have values greater than 1s all the same direction. - ten consecutive control values fall on one side of the mean.

Question 26

QA in the clinical laboratory

Answer 26

Error can occur at several points during the specimen collection, test performance, and results reporting.

Question 27

TQM

Answer 27

Total Quality management - is a program combining both quality control and quality assessment. This ensures quality throughout the total testing process, from ordering test to entering results on the patient charts.

Question 28

Why is QA so important?

Answer 28

- laboratory results are used to help diagnose . prescribe treatment and monitor the patient progress. - they need to be reliable and the lab WC procedures and results must be documented. - lab techs need to ensure quality results and in order to achieve that the QA program needs to happen with every patient results.

Question 29

List important parts of a QC system

Answer 29

- ensure that certain limits for a test results or product is maintained. - control materials, calibrating instruments, instrument maintenance and repair records, comparison of test methods and reagent preparation.

Question 30

How are results generated in laboratory validated?

Answer 30

- all analytical instruments must be calibrated and control must be run with each set of patient samples. - calibrations can be accomplished either by analyzing solutions of known compositions called standards.

Question 31

Control Serum

Answer 31

- also known as control sera - solution that contains the same constituents as those being analyzed in the patient sample. -

Question 32

What is another name for standard?

Answer 32

reference material

Question 33

Why must standard precautions be followed while using the standards and controls?

Answer 33

- techs can be exposed to bloodborne pathogens while using calibrators and controls. - many of the samples are of human origin and although they are screened for certain pathogens, may still be infectious.

Question 34

Explain how one might have precision without accuracy?

Answer 34

- one could produce results near in value to each other but because an error, the values may be inaccurate / not near the true value.

Question 35

Why use a Gaussian curve? And what is the standard deviation range?

Answer 35

- the curve can be divided into percentage divisions. - in a normal distributed population, 68.2% of all results obtained in the analysis will fall between 1s below the mean and 1s above the mean. - must establish the allowable standard deviation for every test performed in the lab. A 2 standard deviation limit is a common choice.

Question 36

Pre-analytical

Answer 36

errors include misidentifying the patient, collecting a sample of blood at the wrong time, mishandling the specimen.

Question 37

Analytical

Answer 37

errors occur during the test procedure and may be random or systematic.

Question 38

Systematic error

Answer 38

a variation that may make results consistently higher or lower than actual values. Factors that may cause this are deteriorated reagents, mechanical trouble in the instrument, or a peculiarity in worker methodology such as manner of popetting.

Question 39

Random error

Answer 39

- cannot be absolutely identified. - causes variations on either side of the mean. Factors that may contribute is air bubbles in reagent lines, difference in technique among workers and certain specimen characteristics.

Question 40

Post-analytical errors

Answer 40

- errors that occur during results reporting. - Ex. results may be accurate but may be transferred to another patient's records by entering the wrong patient identification number in computer. -Ex. when results are transcribed by hand, the wrong value may be copied from laboratory reports to a patient's chart.