STATISTICS EXCLUSIVES PGQUESTIONS

STATISTICS  /PGQUESTIONS

Q. A screening test is performed and there are 10 positive results. Of these, six are false positives. Of note, there are exactly 10 people with disease in the population screened. Which of the following is true?

A. This test has a 40% sensitivity.

B. This test has a 60% sensitivity.

C. This test has a 100% sensitivity.

D. This test has a 60% specificity.

E. This test has a 40% specificity.

Ans:. A.

We know that there are six false positives. Thus, the remaining four positive tests must be true positives. Since there are exactly 10 people with disease, there must be six false negatives. Using this information we can calculate the sensitivity, but not the specificity. Sensitivity is a/(a + c)= 4/10 =0.4, or 40%.

Q. A screening test for diabetes is being evaluated. You know that 900 nondiabetics and 100 diabetics are being screened. There are 100 positive tests and of these, 90 have diabetes.

Which of the following is true in this population?

A. The NPV of the test is 0.9.

B. The NPV of the test is 0.5.

C. The PNV of the test is 0.1.

D. The PPV of the test is 0.1.

E. The PPV of the test is 0.9.

Ans: E.

Ninety of the 100 positive screens have diabetes, so they must be true positives. The remaining

10 must be false positives. Since there are 100 people with diabetes, there must be 10 false negatives as well. So we can calculate PPV but not NPV. The PPV is equal to 90/100 = 0.9.

Q. Given the following collection of data {1,2,4,6,7,8,9}, which is correct?
A. The mean is 5.0.
B. The median is 5.0.
C. The median is 5.5.
D. The median is 6.0.
E. The mean is 6.0.

Ans:. D.

 Given the set of numbers {1,2,4,6,7,8,9}, the sum of these numbers is 37 and there are seven values, so the mean is 37/7 =5and2/7, or 5.28. The median, which is the center of an odd number of values, is the number 6, with 1, 2, and 4 below and 7, 8, and 9 above.

Q. Given the following collection of data {1,1,1,1,2,3,5,5, 6,6,7,7,9,9}, which of the following is correct?
A. The mode is 1.
B. The mean is 4.5.
C. The median is 6.
D. A and B are correct.
E. A and C are correct

Ans. D.

Given the set of numbers {1,1,1,1,2,3,5,5,6,6,7,7,9,9}, there are 14 numbers, and their sum is 63. Thus the mean is 4.5; clearly, the median is 5; and the mode is 1. Thus, the answer is (D), which is a mode of 1 and a mean of 4.5.

Q. You are told that your patient has a cholesterol result that is the mean of that in the population. Which of the following distributions would also mean that his result is necessarily
greater than half of the population?
A. Skewed to the left
B. Skewed to the right
C. Uniform
D. Normal
E. Bimodal

Ans:  B.

The question asks, “In what type of distribution is the mean greater than the median?”The mean will equal the median in normal and uniform distributions. In a symmetric bimodal distribution this will also be true. In a skewed-to-the-left distribution, the median will be greater than the mean, whereas in a skewed-tothe- right distribution, the mean will be greater than the median

Q. Which of the following statements is true about a 95% confidence interval?
A. There is a 95% chance that the true value is in the interval.
B. Ninety-five percent of the time, the true value will fall in the interval.
C. If you repeated the study 20 times, the true value would be in the interval at least once.
D. If the interval does not contain the null hypothesis, you can be 95% certain that your result is the true value.
E. If you repeat the study an infinite number of times, the results would fall in the interval 95% of the time

Ans;E.

What a 95% CI tells you is that if you repeated the same experiment that you did to get your summary statistic (e.g., the mean or proportion), an infinite number of times, 95% of the time you would get a value that falls within the 95% CI. It does not tell you that the true value you are seeking is going to fall within your CI, particularly because your experiment may be faulty or biased; thus, the true value may be missed by the CI. Even with a perfectly performed experiment, the CI is not used to tell you about the true value; it gives just the results of that

particular experiment.

Q. You are designing a study to investigate whether ethnicity is associated with type II DM. You have a cohort of 1000 patients of Asian, African American, Caucasian, and Latino ethnicity. Which of the following tests would be the best to compare the results of the study?
A. Student t test
B. Power analysis
C. z test
D. Chi-square test
E. Bonferroni correction

Ans. D.

In this study design, you are attempting to determine whether there is a difference in any of these groups of patients with respect to the risk for type 2 diabetes. The test that is needed must be able to compare proportions between multiple groups. The only one that can do that is the chi-square test. The student t test is to compare two means; the z test is to compare the proportions of two groups. A power analysis is performed to measure the power of a particular study to reject the null hypothesis. A Bonferroni correction is performed when making more than one comparison, using, for example, a student t test. Using a cutoff of the test that allows a 5% chance of type I error goes awry when you make many comparisons of outcomes in the same study. For example, if you compared 100 different means, on average you would expect five of them to meet the p _ .05 requirement. Thus, a Bonferroni or, more commonly, the student- Newman-Keuls test can be used to adjust the cutoff when making multiple comparisons.

MEDICO LEGAL ETHICS- EXCLUSIVE

Q.) You are a surgeon taking care of three patients in the ED. One has chronic back pain, one has abdominal pain suspicious for appendicitis, and one has a laceration of her hand requiring sutures. You are seeing your third patient who wants to discuss the possibility of scarring and is quite concerned; however, you are paged by the radiologist regarding the CT results on your abdominal pain patient. Which of the following is the likely best provision of care?

A. Because you are currently with your third patient, continue your discussion with her and answer all of her questions.

B. Tell your third patient, “I will be right back,” and go see your first patient, who has been waiting the longest.

C. Tell your third patient, “Let me go arrange a consultation with plastic surgery after I answer this page” and go to answer the page from radiology.

D. Tell your third patient, “Don’t worry; no one will notice this scar,” and go to answer your page.

E. Tell your third patient, “Don’t worry; no one will notice this scar” and suture her hand.

Ans:  C.

 Despite wanting to form a supportive relationship with this patient, allay her fears, and answer her questions, as a physician it is important to be able to prioritize seriously ill patients above less ill patients. In this scenario, the patient with possible appendicitis is top priority, despite patient number 1 having been in the ER the longest. Thus, when radiology pages you regarding this patient, you should answer this page as soon as possible to determine whether this patient needs surgery. However, there are better ways to excuse yourself from your third patient. If you tell her, “I will be right back” and then do not come back for a long time, she is likely to become annoyed. However, if you acknowledge her concerns by consulting plastic surgery and explain quickly that you have another sick patient who requires your care, she is likely to understand and to feel that her waiting is justified. Telling her,“no one will notice this scar” does not acknowledge her concerns about scarring and is inappropriately paternalistic.

Q. You are an obstetrician providing care for a patient in labor. A nurse informs you that the fetal heart rate is experiencing a bradycardia, and on exam there is an umbilical cord prolapse. The patient is being moved to the operating room for an emergency cesarean section. Which of the following describes optimal documentation of this event?

A. Immediately write down your impression of the situation and your plan of action.

B. Go to the patient’s bedside and facilitate the move to the operating room; after the cesarean, write a note documenting what occurred and when.

C. Tell the nurse your plan of action, then postoperatively ,time your note for when you told the nurse of the plan.

D. Write a quick note, and then postoperatively, make changes to the note that reflect what actually occurred.

E. There is no need to document what occurred because nursing will do the documentation.

Ans: B.

In this setting of an emergent procedure needing to be performed, rapid, efficient action is the most important thing. While in most cases it is best to document events as they occur, a physician in this case should act first and worry about documentation second.

Further, there is never an indication to change prior documentation or adjust timing on notes to make it seem as if they were being written prior to when they actually were written. It is useful to communicate the plan of action to the nurse, who is likely to document at some point what that plan was. However, you cannot rely on other practitioners to do your documentation, as everyone may have a different viewpoint on how events occurred. The best way to document

an event of this sort is to deal with the emergency, perform the cesarean section, and move the patient to recovery. Once there, discuss the timing of events with nursing and anesthesia and write a note that reflects your best understanding of what occurred.

Q. A patient you are seeing for the first time has chronic back pain. He wishes to have an immediate MRI and a referral to a neurosurgeon. He tells you this is what his last doctor was going to do. Your best course of action is to:

A. Order the MRI and make the referral.

B. Tell the patient that because this is the first visit, you need to start the work-up of his back pain from the start.

C. Give the patient ibuprofen and order an x-ray of the back.

D. Ask the patient for the name and number of his prior physician and ask him to obtain his prior medical records, and reschedule him in 1 or 2 weeks.

E. Order a CT and refer him to an orthopedic surgeon.

Ans: D.

 It is unclear why this patient has changed physicians. He may have already undergone an extensive work-up for his chronic back pain that you do not need to repeat. If this was a first visit

for this symptom, ibuprofen and an x-ray would be a reasonable way to begin management. However, for this patient, who has likely already used ibuprofen and had x-rays, it is unlikely to contribute to his care. It is also folly to assume that a patient has had the appropriate work-up thus far, as he may have switched providers a number of times and not had good continuity of care. Thus, the most important thing to do is to acknowledge his prior care and attempt to assemble a plan of care with his prior practitioner that is acknowledged as workable by you and the patient.

Q. A physician is caring for a patient with atrial fibrillation and is prescribing medication to anticoagulate her blood. Which of the following actions is most likely to increase the risk of lawsuit.

A. The physician prescribes twice the necessary dosage of medication, but there are no complications and a month later, the dosage is decreased.

B. The physician prescribes the appropriate medication but the patient experiences a stroke despite the treatment. The physician sees the patient daily in the hospital.

C. The physician prescribes the appropriate medication, but the patient experiences a stroke despite the treatment.The physician explains how medication does not always work.

D. The physician prescribes the appropriate medication, but the patient experiences a stroke despite the treatment. The physician allows the hospital team to provide excellent care for the patient and plans to see the patient back in the office after discharge.

E. The physician prescribes the appropriate medication, but the patient experiences a stroke despite the treatment. The physician updates the patient’s family with daily

Changes

Ans: D.

 Answer (A) is the only one that has malpractice. However, because this action did not result in any harm, it is unlikely to lead to a lawsuit. Answers (B), (C), and (E) all involve the physician communicating in an ongoing way with the patient and her family. Although answer (D) results in excellent care, because the physician does not follow up with the patient during her acute event she may feel abandoned. Furthermore, by waiting to follow up with the patient after discharge, if she ends up in a nursing home, goes to a rehabilitation facility, or dies, the physician will not have the opportunity to see the patient at all.

INFECTIVE ENDOCARDITIS

Q. The erythematous painless lesions on palms in the setting of infective endocarditis are called?
A. Osler nodes
B. Roth spots
C. Splinter hemorrhages
D. Janeway lesions
E. Palpable purpura

Ans: D.

In the setting of IE, emboli from the vegetative valvular lesion can lodge in the distal vasculature and immune complexes can form, leading various lesion such as- Osler nodes, Roth spot, Splinter hemorrhages, Janeway lesions.

 Roth spots – is due to Immunologic phenomena- Retinal hemorrhage with a central area of clearing.

Osler nodes- also  Immunologic lesion- Erythematous painful nodes at the tips of digits.

Janeway lesion- Vascular  etiology- Erythematous painless macules lesions on the palms and soles .

Splinter haemorrhage-  Vascular cause- Petechiae underneath the hemorrhages nail bed.