USMLE USMLE Certifications USMLE-STEP-3 Questions & Answers

• Question 171:

  In your role as a physician in a community health center, you agree to perform sports preparticipation examinations on students from the local high school. You have several scheduled for today. Your first appointment is with a 16-year-old male who is planning to run on the cross-country team in the Fall and play baseball in the Spring. He reports that one time he "blacked out" while running, but he has never had chest pain while exercising and he is one of the top runners on the team. He has no known medical history, denies alcohol, tobacco, recreational drug, or performance-enhancing drug use. He has a cousin who died at the age of 21 of "some kind of heart disease," although your patient is not sure of any details. On examination, he is healthy appearing and has normal vital signs, with a pulse rate of 72 and a blood pressure of 100/65. Auscultation of his heart reveals no cardiac murmur while he is lying down, a soft systolic murmur when he stands which increases on having the patient perform a Valsalva maneuver. The remainder of his examination is normal Your next appointment is with a 15-year-old female who plans to play basketball and volleyball. She has no significant medical history, denies a family history of premature cardiac deaths, and denies tobacco, alcohol, recreational drug, or performance-enhancing drug use. She reports having regular menstrual cycles. On examination, she is 72 in. tall, weighs 150 lbs, and has an arm-span of 77 in. Her vital signs are normal. She has a high-arched palate, pectus excavatum, and long, slender fingers. Her cardiac, pulmonary, abdominal, and dermatologic examinations are normal.

  Your management at this point should include further evaluation for the possible diagnosis of which of the following?

  A. Turner syndrome

  B. Marfan syndrome

  C. the female athlete's triad

  D. type 1 diabetes mellitus

  E. atlantoaxial instability

  Correct Answer: B Section: (none)

  Explanation: Explanations: Primary care physicians are frequently called on to perform preparticipation examinations on young athletes. These types of encounters can be used to serve a number of purposes, including attempting to identify conditions that may adversely affect the athlete during participation, identify conditions that may predispose the athlete to injury, provide anticipatory guidance on high-risk behaviors common to the age group being addressed, and fulfill legal conditions of the institution involved. Fortunately, the rate of sudden death in young athletes is low. In those under the age of 35, the most common cause of sudden death is congenital cardiac anomalies. Hypertrophic cardiomyopathy (HCM) is responsible for about onethird of these deaths. Unfortunately, sudden death may be the presenting symptom of HCM. Apersonal or family history of congenital heart disease, symptoms of chest pain or tightness, palpitations, dyspnea, syncope or near-syncope are important. A family history of HCM or unexplained sudden death in someone under the age of 50 is significant as well. The murmur of HCM may not be present in all persons with this disorder.

  To identify the murmur, dynamic auscultation is often necessary. The heart should be auscultated while the patient is lying and then standing. As this murmur is accentuated by maneuvers which reduce cardiac preload, the murmur will get louder when the patient stands or performs a Valsalva maneuver and will diminish as the patient lies or squats. As the patient in question 22 has the concerning historical point of exertional syncope and a family history of an unexplained, early death along with a characteristic murmur on examination, further evaluation is warranted. In the 26th Bethesda Conference report, the American College of Cardiology recommends that persons with HCM should be restricted from all, except possibly for the least strenuous, athletic activity. In this case, restriction of all athletic activity until the patient can be further evaluated by a cardiologist--preferably one with experience in dealing with the evaluation of athletes--would be the most appropriate option of the choices given.

  Marfan syndrome is a connective tissue disorder that typically affects the eyes, skeletal system, and cardiovascular system. Persons with Marfan syndrome are typically tall and have arm spans that are greater than their height. Signs include long, slender digits, high-arched palates, and pectus deformities of the chest. Lens dislocations in the eye are common. Detecting Marfan syndrome during a preparticipation examination is important because of the occurrence of aortic\ root dilation and the risk of sudden death caused by aortic rupture. The patient in questions 23 and 24 has multiple signs of Marfan syndrome and further evaluation would be indicated. Of the options given, an echocardiogram to evaluate the aortic root and to look for other valvular abnormalities would be indicated. These persons usually require referral to an ophthalmologist as well for a dilated eye examination to evaluate for lens dislocations. Turner syndrome is a syndrome of gonadal dysgenesis, associated with a 45, X karyotype (or another defect of the X chromosome). This syndrome is typically associated with a short stature and multiple anomalies including a webbed neck and "shield" chest. The female athlete triad is a syndrome of disordered eating, amenorrhea, and osteoporosis. It is seen most often in participants in activities that emphasize low body weights, such as gymnastics or ballet. The presence of regular menstrual cycles makes this diagnosis unlikely. Atlantoaxial instability can be associated with Down syndrome.

  Physicians performing preparticipation examinations on someone with Down syndrome must consider performing lateral cervical spine x-rays with flexion and extension views. This patient does not have any of the classic findings of Down syndrome. Similarly, she does not exhibit any of the classic symptoms of type 1 diabetes polydipsia, polyphagia, and polyuria. Performing serum glucose testing would therefore not be indicated. The patient in question 25 is the most typical type of patient who presents for a preparticipation examination--the healthy adolescent. This may be the only encounter that a physician will have with an adolescent, especially an adolescent male. It is in this population where a physician can use this encounter to address other age appropriate health maintenance issues. As the patient had a Td booster 3 years ago, another one at this point would not be indicated (although consideration could be given to providing a Tdap). Other vaccinations to consider would be hepatitis B and MMR, if he has not previously been adequately immunized. As he has had two MMR vaccines, he has completed the recommended series. There is no history given regarding hepatitis B vaccination and this would be something to address clinically. A nonjudgmental discussion of sexual behaviors, drug use, alcohol use, and other high-risk behaviors would also be appropriate. Screening athletes who have neither concerning symptoms nor signs with ECGs is not recommended because of the poor predictive values and significant costs involved with mass screening. ECGs should be performed without hesitation in any athlete who has a history, examination finding, or preexisting diagnosis of a potentially high-risk condition. Although some localities may require a urinalysis as part of a preparticipation examination, there is no evidence to recommend universal screening

• Question 172:

  In your role as a physician in a community health center, you agree to perform sports preparticipation examinations on students from the local high school. You have several scheduled for today. Your first appointment is with a 16-year-old male who is planning to run on the cross-country team in the Fall and play baseball in the Spring. He reports that one time he "blacked out" while running, but he has never had chest pain while exercising and he is one of the top runners on the team. He has no known medical history, denies alcohol, tobacco, recreational drug, or performance-enhancing drug use. He has a cousin who died at the age of 21 of "some kind of heart disease," although your patient is not sure of any details. On examination, he is healthy appearing and has normal vital signs, with a pulse rate of 72 and a blood pressure of 100/65. Auscultation of his heart reveals no cardiac murmur while he is lying down, a soft systolic murmur when he stands which increases on having the patient perform a Valsalva maneuver. The remainder of his examination is normal. At this point, what is your most appropriate management option?

  A. allow unrestricted participation in sports

  B. allow participation in noncontact sports

  C. allow him to play baseball but not run cross-country

  D. restrict him from all athletic participation until he is evaluated by a cardiologist

  E. restrict him from competitive athletics but allow him to participate in gym class

  Correct Answer: D Section: (none)

  Explanation:

  Explanations:

  Primary care physicians are frequently called on to perform preparticipation examinations on young

  athletes. These types of encounters can be used to serve a number of purposes, including attempting to

  identify conditions that may adversely affect the athlete during participation, identify conditions that may

  predispose the athlete to injury, provide anticipatory guidance on high-risk behaviors common to the age

  group being addressed, and fulfill legal conditions of the institution involved. Fortunately, the rate of sudden

  death in young athletes is low.

  In those under the age of 35, the most common cause of sudden death is congenital cardiac anomalies.

  Hypertrophic cardiomyopathy (HCM) is responsible for about onethird of these deaths. Unfortunately,

  sudden death may be the presenting symptom of HCM. Apersonal or family history of congenital heart disease, symptoms of chest pain or tightness, palpitations, dyspnea, syncope or near-syncope are important. A family history of HCM or unexplained sudden death in someone under the age of 50 is significant as well. The murmur of HCM may not be present in all persons with this disorder.

  To identify the murmur, dynamic auscultation is often necessary. The heart should be auscultated while the patient is lying and then standing. As this murmur is accentuated by maneuvers which reduce cardiac preload, the murmur will get louder when the patient stands or performs a Valsalva maneuver and will diminish as the patient lies or squats. As the patient in question 22 has the concerning historical point of exertional syncope and a family history of an unexplained, early death along with a characteristic murmur on examination, further evaluation is warranted. In the 26th Bethesda Conference report, the American College of Cardiology recommends that persons with HCM should be restricted from all, except possibly for the least strenuous, athletic activity. In this case, restriction of all athletic activity until the patient can be further evaluated by a cardiologist--preferably one with experience in dealing with the evaluation of athletes--would be the most appropriate option of the choices given.

  Marfan syndrome is a connective tissue disorder that typically affects the eyes, skeletal system, and cardiovascular system. Persons with Marfan syndrome are typically tall and have arm spans that are greater than their height. Signs include long, slender digits, high-arched palates, and pectus deformities of the chest. Lens dislocations in the eye are common. Detecting Marfan syndrome during a preparticipation examination is important because of the occurrence of aortic\ root dilation and the risk of sudden death caused by aortic rupture. The patient in questions 23 and 24 has multiple signs of Marfan syndrome and further evaluation would be indicated. Of the options given, an echocardiogram to evaluate the aortic root and to look for other valvular abnormalities would be indicated. These persons usually require referral to an ophthalmologist as well for a dilated eye examination to evaluate for lens dislocations. Turner syndrome is a syndrome of gonadal dysgenesis, associated with a 45, X karyotype (or another defect of the X chromosome). This syndrome is typically associated with a short stature and multiple anomalies including a webbed neck and "shield" chest. The female athlete triad is a syndrome of disordered eating, amenorrhea, and osteoporosis. It is seen most often in participants in activities that emphasize low body weights, such as gymnastics or ballet. The presence of regular menstrual cycles makes this diagnosis unlikely. Atlantoaxial instability can be associated with Down syndrome.

  Physicians performing preparticipation examinations on someone with Down syndrome must consider performing lateral cervical spine x-rays with flexion and extension views. This patient does not have any of the classic findings of Down syndrome. Similarly, she does not exhibit any of the classic symptoms of type 1 diabetes polydipsia, polyphagia, and polyuria. Performing serum glucose testing would therefore not be indicated. The patient in question 25 is the most typical type of patient who presents for a preparticipation examination--the healthy adolescent. This may be the only encounter that a physician will have with an adolescent, especially an adolescent male. It is in this population where a physician can use this encounter to address other age appropriate health maintenance issues. As the patient had a Td booster 3 years ago, another one at this point would not be indicated (although consideration could be given to providing a Tdap). Other vaccinations to consider would be hepatitis B and MMR, if he has not previously been adequately immunized. As he has had two MMR vaccines, he has completed the recommended series. There is no history given regarding hepatitis B vaccination and this would be something to address clinically. A nonjudgmental discussion of sexual behaviors, drug use, alcohol use, and other high-risk behaviors would also be appropriate. Screening athletes who have neither concerning symptoms nor signs with ECGs is not recommended because of the poor predictive values and significant costs involved with mass screening. ECGs should be performed without hesitation in any athlete who has a history, examination finding, or preexisting diagnosis of a potentially high-risk condition. Although some localities may require a urinalysis as part of a preparticipation examination, there is no evidence to recommend universal screening.

• Question 173:

  You are evaluating a journal article describing a test for the diagnosis of congestive heart failure (CHF). In the study described, 250 consecutive patients were given the test. Of the 250 subjects, 106 tested positive for CHF and 144 tested negative. All 250 subjects were then evaluated by expert cardiologists who were blinded to the results of the experimental test. These cardiologists determined that of the 106 persons who tested positive, 95 actually had CHF. Further, the cardiologists found that of the 144 who tested negative, 2 truly had CHF. What is the negative predictive value (NPV) of this test for the diagnosis of CHF?

  A. 99%

  B. 93%

  C. 90%

  D. 85%

  E. 77%

  Correct Answer: A Section: (none)

  Explanation:

  Explanations:

  Understanding the concepts of sensitivity, specificity, PPV, and NPV is crucial to interpreting diagnostic test

  results. Sensitivity is defined as the percentage of people who have a disease who test positive for that

  disease. Specificity is defined as the percentage of people who are free of a disease who test negative.

  These two concepts are considered characteristics of the specific test in question and are independent of

  the prevalence of the disease in the population. The PPVs and NPVs of a test are the test's clinical

  characteristics and these concepts are directly related to the prevalence of the disease in the population.

  The PPV is the percentage of people who have a positive test result who actually have the disease.

  Similarly, the NPV is the percentage of people who have a negative test result who don't have the disease.

  While the definitions may seem subtly different, the implications are significant. The usual way to calculate

  sensitivity, specificity, PPV, and NPV is with the table, using the following definitions

  

  The definitions of sensitivity, specificity, PPV, and NPV would then be: Sensitivity = a/(a + c)

  Specificity = d/(d + b)

  PPV = a/(a + b)

  NPV = d/(d + c)

  The specific information in this question comes from an article describing a study of B-type natriuretic

  peptide (BNP) for the diagnosis of CHF. The data presented show that 106 persons tested positive using

  the BNP test. After comparison with the "gold standard," in this case, a review by expert cardiologists, 95 of

  these 106 were determined to truly have CHF. Therefore, 11 of the 106 were false positives and 95 were

  true positives. Similarly, 144 persons tested negative using the BNP test. Of these, 142 were confirmed as

  true negatives and 2 were determined to be false negatives.

  Putting these numbers into a table reveals:

  

  The calculations then become:

  Sensitivity = a/(a + c) = 95/(95 + 2) = 98%

  Specificity = d/(d + b) = 142/(142 + 11) = 93%

  PPV = a/(a + b) = 95/(95 + 11) = 90%

  NPV = d/(d + c) = 142/(142 + 2) = 99%

• Question 174:

  You are evaluating a journal article describing a test for the diagnosis of congestive heart failure (CHF). In the study described, 250 consecutive patients were given the test. Of the 250 subjects, 106 tested positive for CHF and 144 tested negative. All 250 subjects were then evaluated by expert cardiologists who were blinded to the results of the experimental test. These cardiologists determined that of the 106 persons who tested positive, 95 actually had CHF. Further, the cardiologists found that of the 144 who tested negative, 2 truly had CHF

  What is the positive predictive value (PPV) of this test for the diagnosis of CHF?

  A. 99%

  B. 93%

  C. 90%

  D. 85%

  E. 77%

  Correct Answer: C Section: (none)

  Explanation:

  Explanations:

  Understanding the concepts of sensitivity, specificity, PPV, and NPV is crucial to interpreting diagnostic test

  results. Sensitivity is defined as the percentage of people who have a disease who test positive for that

  disease. Specificity is defined as the percentage of people who are free of a disease who test negative.

  These two concepts are considered characteristics of the specific test in question and are independent of

  the prevalence of the disease in the population. The PPVs and NPVs of a test are the test's clinical

  characteristics and these concepts are directly related to the prevalence of the disease in the population.

  The PPV is the percentage of people who have a positive test result who actually have the disease.

  Similarly, the NPV is the percentage of people who have a negative test result who don't have the disease.

  While the definitions may seem subtly different, the implications are significant. The usual way to calculate

  sensitivity, specificity, PPV, and NPV is with the table, using the following definitions

  

  The definitions of sensitivity, specificity, PPV, and NPV would then be:

  Sensitivity = a/(a + c)

  Specificity = d/(d + b)

  PPV = a/(a + b)

  NPV = d/(d + c)

  The specific information in this question comes from an article describing a study of B-type natriuretic

  peptide (BNP) for the diagnosis of CHF. The data presented show that 106 persons tested positive using

  the BNP test. After comparison with the "gold standard," in this case, a review by expert cardiologists, 95 of

  these 106 were determined to truly have CHF. Therefore, 11 of the 106 were false positives and 95 were

  true positives. Similarly, 144 persons tested negative using the BNP test. Of these, 142 were confirmed as

  true negatives and 2 were determined to be false negatives.

  Putting these numbers into a table reveals:

  

  The calculations then become:

  Sensitivity = a/(a + c) = 95/(95 + 2) = 98%

  Specificity = d/(d + b) = 142/(142 + 11) = 93%

  PPV = a/(a + b) = 95/(95 + 11) = 90%

  NPV = d/(d + c) = 142/(142 + 2) = 99%

• Question 175:

  You are evaluating a journal article describing a test for the diagnosis of congestive heart failure (CHF). In the study described, 250 consecutive patients were given the test. Of the 250 subjects, 106 tested positive for CHF and 144 tested negative. All 250 subjects were then evaluated by expert cardiologists who were blinded to the results of the experimental test. These cardiologists determined that of the 106 persons who tested positive, 95 actually had CHF. Further, the cardiologists found that of the 144 who tested negative, 2 truly had CHF

  What is the specificity of this test for the diagnosis of CHF?

  A. 39%

  B. 61%

  C. 75%

  D. 93%

  E. 98%

  Correct Answer: D Section: (none)

  Explanation:

  Explanations:

  Understanding the concepts of sensitivity, specificity, PPV, and NPV is crucial to interpreting diagnostic test

  results. Sensitivity is defined as the percentage of people who have a disease who test positive for that

  disease. Specificity is defined as the percentage of people who are free of a disease who test negative.

  These two concepts are considered characteristics of the specific test in question and are independent of

  the prevalence of the disease in the population. The PPVs and NPVs of a test are the test's clinical

  characteristics and these concepts are directly related to the prevalence of the disease in the population.

  The PPV is the percentage of people who have a positive test result who actually have the disease.

  Similarly, the NPV is the percentage of people who have a negative test result who don't have the disease.

  While the definitions may seem subtly different, the implications are significant. The usual way to calculate

  sensitivity, specificity, PPV, and NPV is with the table, using the following definitions

  The definitions of sensitivity, specificity, PPV, and NPV would then be:

  

  Sensitivity = a/(a + c)

  Specificity = d/(d + b)

  PPV = a/(a + b)

  NPV = d/(d + c)

  The specific information in this question comes from an article describing a study of B-type natriuretic

  peptide (BNP) for the diagnosis of CHF. The data presented show that 106 persons tested positive using

  the BNP test. After comparison with the "gold standard," in this case, a review by expert cardiologists, 95 of

  these 106 were determined to truly have CHF. Therefore, 11 of the 106 were false positives and 95 were

  true positives. Similarly, 144 persons tested negative using the BNP test. Of these, 142 were confirmed as

  true negatives and 2 were determined to be false negatives.

  Putting these numbers into a table reveals:

  

  The calculations then become:

  Sensitivity = a/(a + c) = 95/(95 + 2) = 98%

  Specificity = d/(d + b) = 142/(142 + 11) = 93%

  PPV = a/(a + b) = 95/(95 + 11) = 90%

  NPV = d/(d + c) = 142/(142 + 2) = 99%

• Question 176:

  You are evaluating a journal article describing a test for the diagnosis of congestive heart failure (CHF). In the study described, 250 consecutive patients were given the test. Of the 250 subjects, 106 tested positive for CHF and 144 tested negative. All 250 subjects were then evaluated by expert cardiologists who were blinded to the results of the experimental test. These cardiologists determined that of the 106 persons who tested positive, 95 actually had CHF. Further, the cardiologists found that of the 144 who tested negative, 2 truly had CHF.

  What is the sensitivity of this test for the diagnosis of CHF?

  A. 98%

  B. 93%

  C. 75%

  D. 61%

  E. 39%

  Correct Answer: A Section: (none)

  Explanation:

  Explanations:

  Understanding the concepts of sensitivity, specificity, PPV, and NPV is crucial to interpreting diagnostic test

  results. Sensitivity is defined as the percentage of people who have a disease who test positive for that

  disease. Specificity is defined as the percentage of people who are free of a disease who test negative.

  These two concepts are considered characteristics of the specific test in question and are independent of

  the prevalence of the disease in the population. The PPVs and NPVs of a test are the test's clinical

  characteristics and these concepts are directly related to the prevalence of the disease in the population.

  The PPV is the percentage of people who have a positive test result who actually have the disease.

  Similarly, the NPV is the percentage of people who have a negative test result who don't have the disease.

  While the definitions may seem subtly different, the implications are significant. The usual way to calculate sensitivity, specificity, PPV, and NPV is with the table, using the following definitions

  

  The definitions of sensitivity, specificity, PPV, and NPV would then be:

  Sensitivity = a/(a + c)

  Specificity = d/(d + b)

  PPV = a/(a + b)

  NPV = d/(d + c)

  The specific information in this question comes from an article describing a study of B-type natriuretic

  peptide (BNP) for the diagnosis of CHF. The data presented show that 106 persons tested positive using

  the BNP test. After comparison with the "gold standard," in this case, a review by expert cardiologists, 95 of

  these 106 were determined to truly have CHF. Therefore, 11 of the 106 were false positives and 95 were

  true positives. Similarly, 144 persons tested negative using the BNP test. Of these, 142 were confirmed as

  true negatives and 2 were determined to be false negatives.

  Putting these numbers into a table reveals:

  

  The calculations then become:

  Sensitivity = a/(a + c) = 95/(95 + 2) = 98%

  Specificity = d/(d + b) = 142/(142 + 11) = 93%

  PPV = a/(a + b) = 95/(95 + 11) = 90%

  NPV = d/(d + c) = 142/(142 + 2) = 99%

• Question 177:

  A recent study compared two drugs--exemestane and tamoxifen--for the treatment of estrogenreceptor positive breast cancer in postmenopausal women. At the end of the study, 91.5% of the women treated with the drug exemestane and 86.8% of the women treated with tamoxifen were disease free (P < 0.001).

  What is the number needed to treat (NNT) with exemestane compared to tamoxifen to prevent one breast cancer recurrence?

  A. 79

  B. 50

  C. 36

  D. 21

  E. 14

  Correct Answer: D Section: (none)

  Explanation: Explanations: Relative risk is the percentage of subjects who achieve an outcome in one experimental group divided by the percentage of subjects who achieve the same outcome in another group. This statistic is used frequently in placebo-controlled trials, where the comparison occurs between the experimental group and the control group. In the study referenced in this set of questions, the comparison is between two groups who were given two different active medications exemestane and tamoxifen. The outcome studied here is the development of recurrent breast cancer. The data presented state that after the course of treatment, 91.5% of the women in the exemestane group and 86.8% of the women in the tamoxifen group were disease free. Therefore, 8.5% in the exemestane group and 13.2% in the tamoxifen group developed the outcome of recurrent breast cancer. The relative risk is then calculated as 0.085/0.132 = 0.64 = 64%. The relative risk reduction is the percentage by which the risk in one group has been reduced when compared to the other group. In other words, if the rate of an outcome in one group is 100%, the relative risk reduction is the difference between 100% and the measured relative risk. It is calculated by the formula: Relative risk reduction = 1 -relative risk In this example, the relative risk reduction is 1 -0.64 = 0.36 = 36%.

  The ARR, also known as the risk difference, is calculated by subtracting the percentage of subjects who achieve an outcome in one group from the percentage who achieve the outcome in another. In this study, the ARR for those in the exemestane group compared to those in the tamoxifen group is 13.2% -8.5% = 4.7%. The NNT is the number of subjects who need to receive an intervention (such as a medication) in order for one of them to have a beneficial outcome. In this study, the beneficial outcome would be one less case of recurrent breast cancer. The NNT is calculated as 1/ARR. In this case, the NNT = 1/0.047 = 21. In other words, 21 women need to be treated with exemestane in order for there to be one fewer case of recurrent breast cancer compared to women treated with tamoxifen.

• Question 178:

  A recent study compared two drugs--exemestane and tamoxifen--for the treatment of estrogenreceptor positive breast cancer in postmenopausal women. At the end of the study, 91.5% of the women treated with the drug exemestane and 86.8% of the women treated with tamoxifen were disease free (P < 0.001).

  What is the absolute risk reduction (ARR) for the development of recurrent breast cancer for women taking exemestane compared to women taking tamoxifen?

  A. 95.3%

  B. 72%

  C. 64%

  D. 36%

  E. 4.7%

  Correct Answer: E Section: (none)

  Explanation: Explanations: Relative risk is the percentage of subjects who achieve an outcome in one experimental group divided by the percentage of subjects who achieve the same outcome in another group. This statistic is used frequently in placebo-controlled trials, where the comparison occurs between the experimental group and the control group. In the study referenced in this set of questions, the comparison is between two groups who were given two different active medications exemestane and tamoxifen. The outcome studied here is the development of recurrent breast cancer. The data presented state that after the course of treatment, 91.5% of the women in the exemestane group and 86.8% of the women in the tamoxifen group were disease free. Therefore, 8.5% in the exemestane group and 13.2% in the tamoxifen group developed the outcome of recurrent breast cancer. The relative risk is then calculated as 0.085/0.132 = 0.64 = 64%. The relative risk reduction is the percentage by which the risk in one group has been reduced when compared to the other group. In other words, if the rate of an outcome in one group is 100%, the relative risk reduction is the difference between 100% and the measured relative risk. It is calculated by the formula: Relative risk reduction = 1 -relative risk In this example, the relative risk reduction is 1 -0.64 = 0.36 = 36%.

  The ARR, also known as the risk difference, is calculated by subtracting the percentage of subjects who achieve an outcome in one group from the percentage who achieve the outcome in another. In this study, the ARR for those in the exemestane group compared to those in the tamoxifen group is 13.2% -8.5% = 4.7%. The NNT is the number of subjects who need to receive an intervention (such as a medication) in order for one of them to have a beneficial outcome. In this study, the beneficial outcome would be one less case of recurrent breast cancer. The NNT is calculated as 1/ARR. In this case, the NNT = 1/0.047 = 21. In other words, 21 women need to be treated with exemestane in order for there to be one fewer case of recurrent breast cancer compared to women treated with tamoxifen.

• Question 179:

  A recent study compared two drugs--exemestane and tamoxifen--for the treatment of estrogenreceptor positive breast cancer in postmenopausal women. At the end of the study, 91.5% of the women treated with the drug exemestane and 86.8% of the women treated with tamoxifen were disease free (P < 0.001).

  What is the relative risk reduction for the development of recurrent breast cancer for women taking exemestane compared to women taking tamoxifen?

  A. 95.3%

  B. 72%

  C. 64%

  D. 36%

  E. 4.7%

  Correct Answer: D Section: (none)

  Explanation: Explanations: Relative risk is the percentage of subjects who achieve an outcome in one experimental group divided by the percentage of subjects who achieve the same outcome in another group. This statistic is used frequently in placebo-controlled trials, where the comparison occurs between the experimental group and the control group. In the study referenced in this set of questions, the comparison is between two groups who were given two different active medications exemestane and tamoxifen. The outcome studied here is the development of recurrent breast cancer. The data presented state that after the course of treatment, 91.5% of the women in the exemestane group and 86.8% of the women in the tamoxifen group were disease free. Therefore, 8.5% in the exemestane group and 13.2% in the tamoxifen group developed the outcome of recurrent breast cancer. The relative risk is then calculated as 0.085/0.132 = 0.64 = 64%. The relative risk reduction is the percentage by which the risk in one group has been reduced when compared to the other group. In other words, if the rate of an outcome in one group is 100%, the relative risk reduction is the difference between 100% and the measured relative risk. It is calculated by the formula: Relative risk reduction = 1 -relative risk In this example, the relative risk reduction is 1 -0.64 = 0.36 = 36%.

  The ARR, also known as the risk difference, is calculated by subtracting the percentage of subjects who achieve an outcome in one group from the percentage who achieve the outcome in another. In this study, the ARR for those in the exemestane group compared to those in the tamoxifen group is 13.2% -8.5% = 4.7%. The NNT is the number of subjects who need to receive an intervention (such as a medication) in order for one of them to have a beneficial outcome. In this study, the beneficial outcome would be one less case of recurrent breast cancer. The NNT is calculated as 1/ARR. In this case, the NNT = 1/0.047 = 21. In other words, 21 women need to be treated with exemestane in order for there to be one fewer case of recurrent breast cancer compared to women treated with tamoxifen.

• Question 180:

  A recent study compared two drugs--exemestane and tamoxifen--for the treatment of estrogenreceptor positive breast cancer in postmenopausal women. At the end of the study, 91.5% of the women treated with the drug exemestane and 86.8% of the women treated with tamoxifen were disease free (P < 0.001).

  What is the relative risk of developing recurrent breast cancer in a woman treated with exemestane compared to a woman treated with tamoxifen?

  A. 90%

  B. 72%

  C. 64%

  D. 36%

  E. 4.7%

  Correct Answer: C Section: (none)

  Explanation: Explanations: Relative risk is the percentage of subjects who achieve an outcome in one experimental group divided by the percentage of subjects who achieve the same outcome in another group. This statistic is used frequently in placebo-controlled trials, where the comparison occurs between the experimental group and the control group. In the study referenced in this set of questions, the comparison is between two groups who were given two different active medications exemestane and tamoxifen. The outcome studied here is the development of recurrent breast cancer. The data presented state that after the course of treatment, 91.5% of the women in the exemestane group and 86.8% of the women in the tamoxifen group were disease free. Therefore, 8.5% in the exemestane group and 13.2% in the tamoxifen group developed the outcome of recurrent breast cancer. The relative risk is then calculated as 0.085/0.132 = 0.64 = 64%. The relative risk reduction is the percentage by which the risk in one group has been reduced when compared to the other group. In other words, if the rate of an outcome in one group is 100%, the relative risk reduction is the difference between 100% and the measured relative risk. It is calculated by the formula: Relative risk reduction = 1 -relative risk In this example, the relative risk reduction is 1 -0.64 = 0.36 = 36%. The ARR, also known as the risk difference, is calculated by subtracting the percentage of subjects who achieve an outcome in one group from the percentage who achieve the outcome in another. In this study, the ARR for those in the exemestane group compared to those in the tamoxifen group is 13.2% -8.5% = 4.7%. The NNT is the number of subjects who need to receive an intervention (such as a medication) in order for one of them to have a beneficial outcome. In this study, the beneficial outcome would be one less case of recurrent breast cancer. The NNT is calculated as 1/ARR. In this case, the NNT = 1/0.047 = 21. In other words, 21 women need to be treated with exemestane in order for there to be one fewer case of recurrent breast cancer compared to women treated with tamoxifen.