Quality Assurance and Statistics

Question 1

If both the gold standard and your test produce the same positive results, this is called a
(A) True negative
(B) True positive
(C) False positive
(D) False negative

Answer 1

(B) “True positive” is when the test you are using produces the same results as the gold standard.

Question 2

The positive predictive value is used to gauge
(A) How accurate the test is
(B) How sensitive the test is
(C) Ability of predicting abnormal results
(D) Ability of predicting negative results

Answer 2

(C) The positive predictive value (PPV) is used to describe how well a test can predict a positive, or abnormal, result.

Question 3

Using a standard Chi square matrix the equation D÷(D+C) is used for determining what statistic?
(A) Accuracy
(B) Sensitivity
(C) Positive predictive value
(D) Negative predictive value

Answer 3

(D) D÷(D + C) is the formula for negative predictive value (NPV), a statistic that predicts how well a test can find a negative, or normal, result. Notice all the parts of the equation are “negative.” C is false negatives and D is true negatives.

Question 4

Using a standard Chi square matrix which of the following equations is used to determine specificity?
(A) A ÷ (A + B)
(B) D ÷ (D + C)
(C) D ÷ (D + B)
(D) (A + D) ÷ (A + B + C + D)

Answer 4

(C) The equation for specificity, the statistic that states how good a test is at finding disease, is D÷(D+B), where D is true negatives and B is false positives.

Question 5

Which of the following indicates how well a test provides the correct results, regardless of whether the result is positive or negative?
(A) Accuracy
(B) Specificity
(C) Sensitivity
(D) Positive predictive value

Answer 5

(A) Accuracy is how well a test provides the correct result, regardless of whether that result is positive or negative. Accuracy involves all the variables: true positives (A) + true negatives (D) divided by the sum of all the variables (A + B + C + D).

Question 6

What is the purpose of testing and calibrating the pressure machine on a scheduled basis?
(A) To ensure the examination is being performed properly
(B) The hospital’s legal department requires it
(C) To ensure the machine is performing as it is supposed to
(D) To ensure that the sonographers are trained in calibration

Answer 6

(C) Ultrasound and plethysmographic equipment must have checks as part of a routine quality assurance (QA) program. QA is required for all accredited laboratories, but should be performed by nonaccredited laboratories, as well. Performing QA checks helps ensure that any error is not caused by the equipment.

Question 7

When should ultrasound equipment be checked for defects in machine and/or transducers?
(A) At the end of each day
(B) During the examination
(C) On a monthly basis, as required by the accreditation bodies
(D) Before or after each patient

Answer 7

(D) Before a patient is scanned, the transducer and equipment should be checked to ensure there are no cracks in the transducer or cords. After the examination, it is the responsibility of the sonographer to ensure the probe cords and power cord are not run over as part of moving the equipment, and that the machine is cleaned according to laboratory standards. Annual QA checks should be performed by a biomedical technician.

Question 8

What is the hazard of a cracked transducer?
(A) There is a risk that the velocities will be inaccurate
(B) There is a risk that the machine will explode
(C) There is a risk of electrical shock
(D) There is no hazard. If the probe works, it is safe

Answer 8

(C) Roughly 10 to 500 volts of electricity go through the transducer, presenting a potential shock hazard to sonographer and patient. Cracked transducers should immediately be taken out of service.

Question 9

A phantom is designed with a string that moves through a water bath. This phantom would be used to test for
(A) Pressure cuff inflation
(B) Doppler-based velocities
(C) Slice thickness artifact
(D) Contrast resolution

Answer 9

(B) There are different types of Doppler phantoms. One type uses a string in a water bath to mimic flowing blood.

Question 10

Five hundred patients are evaluated by conventional angiography to rule out stenosis of the internal carotid artery. You have designed a new process, called BestGuess®, which you want to compare to the “gold standard” of angiography. Of the 500 patients that had angiography, 150 were positive for stenosis by angiography. Of the 150 patients that were positive by angiography, 80 were positive by BestGuess. Of the 350 patients that were negative by angiography, 180 were negative by BestGuess.
What is the sensitivity of the new test?

Answer 10

The Chi square is as follows:
True positives (A): 80
False positives (B): 170
False negatives (C): 70
True negatives (D): 180

Sensitivity is determined by the equation A ÷ (A + C), where A is the true positives and C is the false negatives. The answer is 80 ÷ 150 = 53%.

Question 11

The Chi square is as follows:
True positives (A): 80
False positives (B): 170
False negatives (C): 70
True negatives (D): 180

What is the specificity of the new test?

Answer 11

Specificity is determined by the equation D ÷ (D + B), where D is the true negatives and B is the false positives. The answer is 180 ÷ 350 = 51%.

Question 12

the Chi square is as follows:
True positives (A): 80
False positives (B): 170
False negatives (C): 70
True negatives (D): 180

What is the accuracy of the new test?

Answer 12

Accuracy is determined by the equation (A + D) ÷ (A + B + C + D), where A is the true positives and B is the false positives, divided by all the values in the Chi square. The answer is 250 ÷ 500 = 52%.

Question 13

The Chi square is as follows:
True positives (A): 80
False positives (B): 170
False negatives (C): 70
True negatives (D): 180

What is the positive predictive value of the new test?

Answer 13

The positive predictive value (PPV) is determined by the equation A ÷ (A + B), where A is the true positives and B is the false positives. The answer is 80 ÷ 250 = 32%.

Question 14

The Chi square is as follows:
True positives (A): 80
False positives (B): 170
False negatives (C): 70
True negatives (D): 180

What is the negative predictive value of the new test?

Answer 14

The negative predictive value (NPV) is determined by the equation D ÷ (D + C), where D is the true negatives and C is the false negatives. The answer is 180 ÷ 250 = 72%.

Question 15

A test is developed that is very good at identifying a certain disease, but it only finds the disease about half the time. This test has a low \_\_\_\_\_\_ and a high \_\_\_\_\_\_
(A) Sensitivity, accuracy
(B) Specificity, sensitivity
(C) Accuracy, specificity
(D) Sensitivity, specificity

Answer 15

“(B) The test described can identify a specific disease (high specificity), but it is not good at finding that disease (low sensitivity). An example of this type of test is anti-DNA for systemic lupus erythematosus (SLE). When the test is positive, it is very specific for SLE. However, the patient might have SLE and a negative anti-DNA because the test is not sensitive. In other words, the test may be negative even if the patient has active disease.

Question 16

A test is developed that is very good at determining when disease is not present. This test is said to have a high
(A) Negative predictive value
(B) Positive predictive value
(C) Accuracy
(D) Sensitivity

Answer 16

(A) The negative predictive value (NPV) is high when a test is good at saying that the study is normal; no disease is present.

Question 17

Mammograms are radiographs of the breast that are very good at finding disease in many cases, but not very good at classifying the disease because both cysts and solid masses appear radiopaque (“white”). This type of test has a high \_\_\_\_\_\_ but a low \_\_\_\_\_\_
(A) Sensitivity, accuracy
(B) Specificity, sensitivity
(C) Accuracy, specificity
(D) Sensitivity, specificity

Answer 17

(D) Mammograms are very good at finding pathology, but not very good at classifying if the pathology is a cyst or a solid mass. Therefore, mammography is said to have a high sensitivity, but low specificity.

Question 18

Which of the following is true about HIPAA?
(A) It is actually spelled HIPPA
(B) It specifies criminal and civil penalties for violating patient confidentiality
(C) It only applies to hospital employees
(D) Celebrities are not covered under HIPAA because they are in the public eye

Answer 18

(B) HIPAA, the Health Insurance Portability and Accountability Act, provides for criminal and “civil penalties if protected health information (PHI) is used or accessed inappropriately. Celebrities are protected by HIPAA the same as any other person. The only records the sonographer should access are those of patients with whom they have direct contact as part of their care.

Question 19

Laboratory quality improvement is needed because
(A) Vascular sonographers are very messy
(B) Equipment is always breaking
(C) Vascular laboratories constantly need to maintain or improve standards
(D) You will not get paid if you do not do it

Answer 19

(C) Continuous quality improvement is vital to ensure that patients receive the appropriate test for the clinical diagnosis, that the test is performed correctly, and that the sonographers meet the standards set forth by the laboratory and/or accreditation body.

Question 20

Which of the following is a computer-based file storage device used by institutions to electronically store images and reports?
(A) Matrix camera
(B) Kodak film
(C) PACS
(D) Canon scanner

Answer 20

(C) The PACS is a picture archiving and communication system that involves a computer or network that is used to store images and reports digitally. Institutions with PACS are referred to as “filmless” because hard copy film is no longer used.

Question 21

Who is responsible for ensuring the correct patient is being scanned, the correct study is being performed, and the correct body part is being imaged?
(A) The ordering physician
(B) The nurse
(C) The front desk clerk
(D) The sonographer

Answer 21

(D) The sonographer is the gate keeper to ensure that the correct patient is being scanned (check for at least two identifiers), the correct study is being performed (based on a clinical history), and the correct body part is being scanned (again, based on a history). If an invasive procedure is being performed, a “time out” is required so everyone agrees on the procedure being performed.

Question 22

For which patients should prior examinations be reviewed?
(A) Patients that had studies performed within the last 12 months
(B) Any time priors are available
(C) When the doctor tells you to
(D) For all portable studies

Answer 22

(B). If the patient has had a study performed before, prior examination reports should be reviewed. In the presence of pathology or complicated results, like with graft studies, the prior images should also be reviewed, if obtainable.

Question 23

Seventeen patients had a CTA performed that was positive for 70% stenosis of the ICA. Ultrasound only revealed 11 patients with similarly positive results. What is the sensitivity of the ultrasound?

Answer 23

Sensitivity is determined by true positives divided by (true positives + false negatives), or A ÷ (A + C). In this example, the results are (11) ÷ (11 + 6) = 65%.

Question 24

Fifty patients had a negative MRA for mesenteric stenosis. Of those patients, 40 were negative by ultrasound. What is the specificity of the ultrasound?

Answer 24

Specificity is determined by true negatives divided by (true negatives + false positives), or D ÷ (D + B). In this example, the results are 40 ÷ (40 + 10) = 80%.

Question 25

What is the sensitivity of your test if the true positives’ number is 70 and the false negatives’ number is 10?

Answer 25

Sensitivity is determined by true positives divided by (true positives + false negatives), or A ÷ (A + C). In this example, the results are 70 ÷ (70 + 10) = 87.5%, or 88%.