Quality Control

Question 1

A part of Quality assurance program (internal quality control).
It evaluates the validity of laboratory results before reporting.
Aims to identify and correct errors to ensure accuracy and precision.

Answer 1

QUALITY CONTROL (QC)

Question 2

refers to closeness of measured value of an analyte to its true value.

Answer 2

ACCURACY

Question 3

Also known as detection limit.
The lowest concentration of substance that can be detected by test method.
High sensitivity decrease false (-)
Desirable for screening test

Answer 3

Analytical sensitivity

Question 3

proportion of population with disease who will be positive for result.
Also known as true POSITIVE RATE.

Answer 3

Diagnostic sensitivity

Question 3

the degree of closeness or agreement among values between repeated measurements.

Answer 3

PRECISION/REPRODUCIBILITY

Question 4

Ability of test method to measure only the target analyte and not the other related substances.
High specificity decreases false (+) and cross reactivity.
Desirable for confirmatory test.

Answer 4

Analytical specificity

Question 5

proportion of population without disease who will be negative for result.
Also known as TRUE NEGATIVE RATE.

Answer 5

Diagnostic specificity

Question 6

a set of values with upper and lower limits based on a healthy individual (120 person).

Answer 6

REFERENCE interval (normal values)

Question 7

Use to compared with patient value for laboratory interpretation.

Answer 7

REFERENCE interval (normal values)

Question 8

Also known as LINEARITY.

Answer 8

Reportable range

Question 9

Range of values over which lab can verify accuracy of the test system.
Provided by the manufacturer and verify by testing 20 normal samples.

Answer 9

Reportable range

Question 10

comparison of patient data with previous result (24-48 hours interval). It determine if the changes is due to medical or lab error.

Answer 10

Delta check-

Question 11

test value that considered as life threatening. Glucose, electrolytes, total bilirubin and blood gases are list typically. Immediate notification to health care personnel should be done.

Answer 11

Critical values-

Question 12

Internal quality control
Part of analytical phase of QA
the testing of control together with the patient sample.
Monitors the accuracy and precision of analytical method on a daily basis and detects any error

Answer 12

Intralab QC

Question 13

External quality control
Testing of proficiency sample with unknown concentration.
Participated by different laboratories.
Maintain long term accuracy of the analytical method.
The gold standard for proficiency testing is the College of American pathologist (CAP).

Answer 13

Interlab QC

Question 14

check the stability of the instrument/machine, quality of reagent, and technical error.

Answer 14

Quality control

Question 15

a solution with precise known concentration used to identify and determine the concentration of the sample. Not serum or plasma based

Answer 15

STANDARD

Question 16

a solution or device with known concentration or activity that is used to calibrate, adjust , or graduate measurement of an instrument to match a known input. Serum or plasma based.

Answer 16

CALIBRATOR

Question 17

a patient-like material made from human serum.
Used to run with patient samples.
Used to monitor the performance of an instrument after calibration.
Measure precision/reproducibility

Answer 17

Control

Question 18

used to evaluate overall precision of 2 different methods or instruments and reagents.

Answer 18

COEFFICIENT VARIATION

Question 19

used in external quality assessment program or a proficiency testing program.

Answer 19

Standard deviation index

Question 20

Types of Quality control chart

Answer 20

Gaussian normal distribution graph
Cumulative sum graph
Youden/twin plot
Shewhart Levey-Jennings chart

Question 21

Population probability distribution that is symmetric about the mean.
Also known as normal distribution curve.

Answer 21

Gaussian curve ( bell shape curve)

Question 22

It identifies the consistent problem and requires computer for implementation.

Answer 22

Cumulative sum graph (CUSUM)

Question 22

This plot is indicator of systemic error (trend) and can be used with the 1s rule. Results are out of control when slopes exceeds 45 degrees.

Answer 22

Cumulative sum graph (CUSUM)

Question 23

The most widely used QC chart Illustrate the overall distribution of QC values for interpretation. Used to graph successive/ day to day control values. At least 20 measurements

Answer 23

Shewhart Levey-Jennings chart

Question 23

Used to compare results obtained on a high and low control serum from different laboratories. Display the results of the analyses by plotting the mean value for one specimen on the y-axis and the other specimen for x-axis. Points falling at the center within a 45 degree line- proportional error. Points falling at center outside of 45 degree- constant error

Answer 23

Youden/twin plot

Question 24

a representation of vertically oriented Gaussian curve.

Answer 24

Shewhart Levey-Jennings chart

Question 25

approximation of distribution within a normal distribution.

Answer 25

Empirical Rule

Question 26

the midpoint or middle value of a distribution. To determine arrange the data in numerical order (ascending order).

Answer 26

Median

Question 27

is the frequent observation in a data set.

Answer 27

Mode

Question 28

expression of spread or distribution. To determine subtract the highest data to lowest data.

Answer 28

Range

Question 29

sudden change in data for several days. 6 or more consecutive values are observed only on one side of the mean. The main cause is improper calibration of instrument.

Answer 29

Shift (bias)-

Question 30

6 or more values move continuously in one direction. Hard to notice because it looks like a shift. Main cause is reagent deterioration.

Answer 30

Trend

Question 31

Any value outside established limit (+/-3s). It is significant if occurs more than once in 20 successive runs, caused by systematic or random error.

Answer 31

Outlier

Question 32

Uses two or more control rules to evaluate the QC data, and then rejects a run if any one of these is present.

Answer 32

Multi rule system

Question 33

a single value is outside ±2s limits. Indicate a systematic or random error.

Answer 33

12s

Question 34

any value outside ±3s limits. Indicates a random error

Answer 34

13s

Question 35

there is at least 4 differences between control values within a single run. Indicates a random error only.

Answer 35

R4s

Question 36

2 consecutive values outside the ±2s limits. Indicates systemic error.

Answer 36

22s

Question 37

3 consecutive values outside ±1s limits. Systematic error

Answer 37

31s

Question 38

4 consecutive values outside ±1s limits. Systematic error

Answer 38

41s

Question 39

10 control results on the same side of the mean regardless of SD which they are located. Systematic error.

Answer 39

10x