Test Validation/QA

Question 1

Parameters commonly used to judge efficacy of a diagnostic test:

Answer 1

Sensitivity
Specificity
Accuracy

Question 2

The gold standard test for carotid artery stenosis

Answer 2

Digital subtraction angiography

Question 3

Gold standard for deep vein thrombosis

Answer 3

Venography

Question 4

If no gold standard test, then only autopsy can be used.

T/F

Answer 4

False, sometimes clinical info or findings at surgery can be used

Question 5

What does true positive mean?

Answer 5

Testing procedure demonstrates disease and disease is really present

Question 6

What does true negative mean?

Answer 6

Test and gold standard both said there was no pathology

Question 7

What does false positive mean?

Answer 7

Test said pathology is present, gold standard said no pathology present

Question 8

False negative is when:

Answer 8

Test - normal

Gold standard - abnormal

Question 9

How do you find the sensitivity of a test?

Answer 9

True Pos divided by true pos plus false neg

TP/TP+FN

Question 10

Sensitivity is the ability of a test to:

Answer 10

Detect disease

Question 11

Sensitivity measures how often a test will:

Answer 11

Miss real disease

Question 12

Minimizing false negatives decreases sensitivity.

T/F

Answer 12

False, increases

Question 13

How would you find specificity?

Answer 13

True neg divided by true neg plus false pos

TN/TN+FP

Question 14

Specificity is the ability of a test to:

Answer 14

Identify normality or rule out pathology

Question 15

Specificity is a measurement of:

Answer 15

How real a disease finding by that exam is

Question 16

Decreasing false positives will:

Answer 16

Increase specificity

Question 17

How do you find overall accuracy?

Answer 17

True pos plus true neg divided by total # of tests

TP + TN/total #

Question 18

Accuracy quantifies the tests ability to:

Answer 18

Give correct answer

Question 19

Accuracy should be left as

Answer 19

A fraction

Question 20

What does PPV stand for?

Answer 20

Positive predictive value

Question 21

What figures are required for PPV?

Answer 21

Only positive figures

Question 22

How would you find PPV?

Answer 22

True pos divided by true pos plus false pos

TP/TP+FP

Question 23

PPV tells you how meaningful a

Answer 23

Positive result really is

Question 24

A test with a low positive predictive value cannot be used as an initial screening tool.
T/F

Answer 24

false, it may be useful but further testing may be recommended

Question 25

PPV and NPV are represented as:

Answer 25

Fractions

Question 26

NPV is:

Answer 26

Negative predictive value

Question 27

How do you find NPV and what does it tell us?

Answer 27

True neg divided by true neg + false neg TN/TN+FN How meaningful a negative result really is

Question 28

A test with a low negative predictive value is likely to miss disease and puts the patient in danger. T/F

Answer 28

True

Question 29

How would you find prevalence?

Answer 29

True pos plus false neg divided by total # of tests | TP+FN/Total #

Question 30

Prevalence validates the test. | T/F

Answer 30

False, only shows the proportion of sample population that have pathology being tested for

Question 31

Important qualities of an initial screening test:

Answer 31

High sensitivity Low false neg rate Low risk, low cost Low specificity is acceptable

Question 32

Qualities of a diagnostic test to determine treatment:

Answer 32

High specificity Low false positive rate Low sensitivity is acceptable if known

Question 33

Example of initial screening test

Answer 33

ABI for arterial disease of LE, high sensitivity with little info on area/extent of disease Duplex US or angiography can test that

Question 34

Example of diagnostic test

Answer 34

US for gallstones, ectopic pregnancies, appendix | Tests may not detect all of pathology but surgery can be reliably planned based on pos finding

Question 35

What is quality assurance?

Answer 35

Routine, periodic evaluation of sonography equipment and transducers

Question 36

QA detects image quality problems and assures proper operation of equipment before it effects the:

Answer 36

Images or causes equipment to fail

Question 37

Preventative maintenance is usually performed once a year by appropriate service personnel. T/F

Answer 37

False, 2-3 times

Question 38

Results of QA are compared to:

Answer 38

Past results to identify if change is necessary to unit

Question 39

Everyday maintenance of unit:

Answer 39

Cleaning transducers Inspecting cables Keeping unit dust and dirt free

Question 40

File of QA documents includes:

Answer 40

``` Original equipment purchase order Equipment specs Warranty Results of QA performed Documentation of problems Follow up service report Preventative maintenance reports ```

Question 41

Reports are needed to document the need to replace equipment but not necessary for accreditation. T/F

Answer 41

False

Question 42

AIUM 100 mm test object is composed of:

Answer 42

Series of .75 mm diameter stainless steel rods arranged in groups in transparent plastic tank filled with mixture of alcohol and water that is equal to 1.54 mm/us at room temp

Question 43

The AIUM 100 mm test object is used more commonly with current technology. T/F

Answer 43

False

Question 44

The AIUM 100 mm test object cannot evaluate:

Answer 44

Gray scale or contrast resolution

Question 45

Embedded in the gel of the tissue phantom are several groups of fibers which can be used to evaluate:

Answer 45

``` Axial res Lateral res Depth calibration Image uniformity Distance accuracy ```

Question 46

Inner material of the phantom is gelatin based so in extreme temperatures the base will change its consistency but it’s still okay to use. T/F

Answer 46

False

Question 47

What is the dead zone ?

Answer 47

Distance between transducer face to area in near field that cannot be used due to reverb or transducer design

Question 48

Axial res is tested by scanning rod group located:

Answer 48

In the middle | Placed in oblique plane

Question 49

The largest separation of two closest rods seen represents axial res. T/F

Answer 49

False, smallest

Question 50

Lateral resolution is found by scanning the:

Answer 50

Same rod group as with axial res

Question 51

How is system sensitivity measured?

Answer 51

Of the weakest echo sign visualized determined by gain setting with no TGC using the bottom rod of the group is six vertical equidistant rods

Question 52

Face A of test object is used to test:

Answer 52

Dead zone and axial res

Question 53

Face b is used to test:

Answer 53

Lateral res

Question 54

Elevational res can be documented using:

Answer 54

Tissue phantom or inclined plane phantom

Question 55

Limitation of using tissue phantom for slice thickness testing:

Answer 55

Cystic objects suspended in phantom at certain depths that cannot be changed. Elevational focus must coincide with this depth or can’t be evaluated

Question 56

Inclined plane phantom uses an interface oriented at:

Answer 56

45 degree angle

Question 57

A horizontal band is formed when testing for slice thickness. How is it measured?

Answer 57

The axial height equals slice thickness

Question 58

Some phantoms have a series of gray scale targets that range in contrast from:

Answer 58

+15dB to -15dB

Question 59

Doppler phantoms may contain:

Answer 59

A tube embedded in tissue mimicking medium connected to pump that pushes fluid through at adjustable velocities OR A string that moves immersed in water bath using echoes from vibrating string to imitate reflections from blood cells

Question 60

Using Doppler phantoms, what can be evaluated?

Answer 60

Sensitivity Sample volume accuracy Doppler angle accuracy Max depth of detectable Doppler signal