Lecture 11b - Quality Part 2

Question 1

Define sensitivity

Answer 1

The proportion of cases HAVING a specific disease or condition that gives a POSITIVE test result.

Question 2

Define specificity

Answer 2

The proportion of cases with ABSENCE of a specific disease or condition that gives a NEGATIVE test result.

Question 3

Define true positive

Answer 3

Positive test result and have the disease

Question 4

Define true negative

Answer 4

Negative test result and do not have the disease

Question 5

Define false positive

Answer 5

Positive test result but do not have the disease

Question 6

Define false negative

Answer 6

Negative test result but does have the disease

Question 7

How is sensitivity measured?

Answer 7

It measured how much of a given substance is measured.

The more sensitive the test = the smaller the amount of assayed substance that is measured (detected)

Question 8

How do we find percent sensitivity?

Answer 8

Question 9

Define predictive value.

Answer 9

The ability to predict the results of an analysis of the same data by using another test instrument or measurement; contributes to the validity of a test.

Question 10

How do we determine positive predictive value?

Answer 10

Question 11

How do we determine negative predictive value?

Answer 11

Question 12

Define mean

Answer 12

Mathematical average taken by adding up all of the values in a data set and then dividing the total by the number of results in the data set.

Question 13

Define median

Answer 13

Middle value of a body of data

Question 14

Define mode

Answer 14

The value most frequently occurring in a body of data.

Question 15

Define standard deviation (s or SD)

Answer 15

A measure of the spread, or variability, in a data set.

Question 16

Define variance

Answer 16

The precision of a group of numbers

Question 17

Define coefficient of variation (CV)

Answer 17

Calculates the SD as a “percent of the mean”.

Can be used to compare SDs of two samples.

Question 18

How would a lab determine a control range?

Answer 18

1. Run an aliquot of control sample daily for 15-25 days
2. Treat exactly like a patient
3. Calculate the mean
4. Calculate the variation from the mean using SD
5. +/- 2SD

Question 19

What is a Levy Jennings chart?

Answer 19

A statistical chart used to measure changes in quality control values.

Question 20

What is a shift in QC?

Answer 20

A sudden and sustained change in one direction in control sample values.

Causes - a sudden malfunction with an instrument, QC contamination, etc.

Question 21

What is a trend (or drift) in QC?

Answer 21

A gradual change in the control sample results; control value directions moves progressively in one direction from the mean for at least three days.

Causes - deterioration of reagents, instrumentation, or the control sample.

Question 22

What is a dispersion in QC?

Answer 22

When a random error or lack of precision increases.

Causes - instability problems with instrumentation.

Question 23

Define as a shift, trend, or dispersion.

Answer 23

Shift

Question 24

Define as a shift, trend, or dispersion.

Answer 24

Trend

Question 25

Define as a shift, trend, or dispersion.

Answer 25

Dispersion

Question 26

What are Westgard Rules?

Answer 26

Rules formulated to analyze data in control charts based on statistical methods.

Question 27

When is a 1-2S violated?

Answer 27

Violated when one of two control results falls outside of 2SD.

Warning rule; specimens not rejected.

Question 28

When is a 1-3S violated?

Answer 28

Violated when any QC result falls outside of 3 SD.

Question 29

When is a 2-2S violated?

Answer 29

Violated when two consecutive control values for the same level fall outside of 2 SD in the same direction, or when both control levels in the same test batch exceed 2 SD.

Patient results cannot be reported.

Question 30

When is a 3-1S violated?

Answer 30

Violated when 3 consecutive control results are greater than 1 SD and on the same side of the mean.

Indicates systematic bias.

Question 31

When is a 4-1S violated?

Answer 31

Violated when four consecutive control results are greater than 1 SD on the same side of the mean.

Indicates systematic bias.

Question 32

When is a R-4S violated?

Answer 32

Violated when one control measurement exceeds the +2 SD and the other exceeds the -2 SD control limit.

Patient results cannot be reported.

Question 33

When is Nx violated?

Answer 33

Violated when 7, 8, 9, 10, or 12 control results are on the same side of the mean.

Indicates systematic error.

Question 34

When is 10x violated?

Answer 34

Violated when 10 consecutive QC results for one level of assay control are on one side of the mean OR both levels of control have five consecutive results that are on the same side of the mean.

Patient results cannot be reported.

Question 35

What QC rules are being violated?

Answer 35

1-2S and 1-3S

Question 36

What QC rules are being violated?

Answer 36

2-2S and 3-1S

Question 37

What QC rules are being violated?

Answer 37

4-1S and R-4S

Question 38

What QC rules are being violated?

Answer 38

Nx and 10x

Question 39

What are some nonanalytical factors for quality assessment?

Answer 39

Qualified personnel, established laboratory policies and procedure manual, test requisitioning, patient identification and specimen labeling, specimen transportation and processing, preventative maintenance of equipment.

Question 40

What must a test requisition include?

Answer 40

• Patient ID information
• Time and date of specimen collection
• Source of specimen
• Analyses to be performed

Question 41

How many patient identifiers are needed prior to specimen collection? What are they?

Answer 41

Two; these include:

• First and last name
• Date of birth
• Medical Record Number (MRN)

Question 42

How quickly should a test be performed to ensure accurate results?

Answer 42

2 hours

Question 43

Define turn around time (TAT)

Answer 43

The amount of time in which the test should be completed (determined by laboratory).