USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 391:

  A 45-year-old male living in a homeless shelter is exposed to TB from a fellow resident. He is found to have a 15 mm of induration on the Mantoux skin test. Which of the following risk factors will increase the man's likelihood of developing active TB subsequent to his infection?

  A. history of cough variant asthma

  B. silicosis

  C. chronic obstructive pulmonary disease (COPD)

  D. bronchitis

  E. siderosis

  Correct Answer: B

  Silicosis is considered a risk factor for the development of active TB disease for those who have contracted the infection. HIV infection, malnutrition, IV drug use, alcoholism, leukemia and other cancers, poorly controlled diabetes, severe kidney disease, immune system suppression caused by medications such as drugs to prevent rejection of a transplanted organ, and living in crowded indoor conditions, are also considered risk factors for progression to active disease. Cough variant asthma and bronchitis are not included in this list. COPD can occur as a consequence of chronic TB disease and is not considered one of the risk factors. Siderosis results from accumulation of nonfibrogenic iron oxide particles in the lung and is not considered to predispose to TB.

• Question 392:

  You are examining the relationship between hypertension and myocardial infarction (MI) in your community. In order to do so, you send a questionnaire to the whole population in your community (1000 persons). All 1000 persons responded. The results obtained from that questionnaire are presented below in table.

  

  If we compare the population sample examined with the whole population that responded to the questionnaire, which of the following statements accurately describes the available information?

  A. The sample group confirms the findings of the questionnaire.

  B. As expected, there is a higher "real" incidence of hypertension than reported.

  C. As expected, there is a higher "real" incidence of MI than reported.

  D. There is a statistical test that could be applied to assess the significance of the differences.

  E. The data as presented are not really adequate for further statistical examination.

  Correct Answer: E

  In a questionnaire relating to history, patients' knowledge as to whether or not they have hypertension or have had an MI might be sufficiently accurate to allow further statistical analysis. The data provided in this questionnaire are not adequate for more detailed statistical analysis. The questionnaire responses rely on memory recall, which at best is questionable, for comparison with an actual examination. Criteria for establishing a diagnosis of MI and, if possible, actual blood pressure readings, as well as a definition of hypertension, are required. The crux of epidemiologic analysis is a detailed criterion for establishing a diagnosis. With this additional information, relevant statistical tests could be applied. In the absence of this information, any further statistical analysis is likely to lead to misleading results.

• Question 393:

  You are examining the relationship between hypertension and myocardial infarction (MI) in your community. In order to do so, you send a questionnaire to the whole population in your community (1000 persons). All 1000 persons responded. The results obtained from that questionnaire are presented below in table.

  

  You randomly select a sample of 100 questionnaires in order to determine how representative your results would have been compared to the whole population if you had originally only sampled 100 individuals from your community. The results obtained are shown below in table.

  

  Which of the following statistical tests could best be used to determine whether there is a significant increase in the history of MI among those persons who have hypertension in comparison with those without hypertension?

  A. t-test, single-tailed

  B. t-test, two-tailed

  C. test of variance

  D. P value

  E. chi-square test

  Correct Answer: E

  The chi-square test is the most appropriate statistical test to determine whether series of frequencies or proportions are significantly different from each other. It is designed to describe with a single number how much the frequencies in each cell of a box of paired readings differ from the frequency we would expect if there were no relationship between the observed readings. If the observed readings are similar to expected readings, the chi-square will be a small number. If there is a greater difference, the chi- square will be larger. The mathematical equation is:

  

• Question 394:

  You are examining the relationship between hypertension and myocardial infarction (MI) in your community. In order to do so, you send a questionnaire to the whole population in your community (1000 persons). All 1000 persons responded. The results obtained from that questionnaire are presented below in table.

  

  What is the prevalence of MI per 1000 persons in the community?

  A. 5

  B. 10

  C. 15

  D. 20

  E. 25

  Correct Answer: D

  In the study described in the question, the prevalence rate is the total number of cases occurring in the community, divided by the number of members in the community, multiplied by 1000. This is a point prevalence rate: the number of individuals who have had an MI at the time the questionnaire is administered. Thus, the prevalence is (20/1000). 1000 = 20.

• Question 395:

  You are examining the relationship between hypertension and myocardial infarction (MI) in your community. In order to do so, you send a questionnaire to the whole population in your community (1000 persons). All 1000 persons responded. The results obtained from that questionnaire are presented below in table.

  

  What is the prevalence of MI per 1000 hypertensive persons in the total population?

  A. 10

  B. 15

  C. 19

  D. 75

  E. 81

  Correct Answer: D

  In the tables that accompany the question, the number of hypertensive personsin the community is 200. The number of patients with hypertension who also report a history of MI is 15. The prevalence is therefore 15 in a population of 200, which may be translated as a rate of 75 per 1000.

• Question 396:

  You are examining the relationship between hypertension and myocardial infarction (MI) in your community. In order to do so, you send a questionnaire to the whole population in your community (1000 persons). All 1000 persons responded. The results obtained from that questionnaire are presented below in table.

  

  What is the reported prevalence of hypertension in the population per 1000?

  A. 150

  B. 185

  C. 200

  D. 220

  E. 250

  Correct Answer: C

  Prevalence is the number of existing cases of a disease occurring in the total population at a given period of time. In this study, the prevalence rate is calculated based on reported figures (15 + 185 = 200 persons per 1000 persons surveyed report having hypertension). The actual figure, as demonstrated by the investigation of the sample, is likely to be higher.

• Question 397:

  You have decided to survey the population to establish a health risk profile for the population. Due to budget constraints, you must gather data using a stratified random sample. This approach is correctly described as which of the following?

  A. based on selecting individuals from a list at predetermined intervals (every ith individual)

  B. random sampling of separate segments of a population

  C. randomly grouping the population

  D. sampling a cluster of individuals

  E. removing outliers and sampling from remainder of group

  Correct Answer: B

  Sometimes it is possible to identify subgroups or strata of a population. Randomly sampling these segments, called strata, may reduce sampling error. Systematic sampling, selecting every "ith" individual, is not necessarily random, depending on how lists are constructed. Random groups would presumably be based on random selection of individuals, and little benefit would derive from studying such groups. Random groups produce more hazards statistically than randomized strata. Clusters are somewhat different; they may be small groups of the population occurring in specific areas, such as families, villages, or wards. The characteristics of clusters are not necessarily those of the population, but more those of location. Cluster sampling may be useful but does not have the same outcome as a stratified sample.

• Question 398:

  Age-adjusted cancer death rates for men and women reveal an increasing rate for which cancer over the last 20 years?

  A. prostate cancer

  B. lung cancer in women

  C. breast cancer

  D. colorectal cancer

  E. stomach cancer

  Correct Answer: B

  The age-adjusted lung cancer mortality rate rose rapidly following adoption of smoking by women. This now has stabilized as the leading cause of cancer death in women.

• Question 399:

  Jehovah's Witnesses usually refuse to consider a recommended blood transfusion. A 5-yearold child with hemophilia and dangerously low hemoglobin levels needs such a transfusion, but the Jehovah's Witness parents refuse to accept the recommendation. How are principles of autonomy best resolved?

  A. The hospital's representatives respect the parents' right to consent and support their refusal.

  B. The physician explains the need, in simple words, to the child who refuses the transfusion.

  C. The hospital requests a local court to exercise the rights of the child through the appointment of a surrogate guardian.

  D. The local court gives the physician the right to decide if the transfusion is warranted.

  E. The hospital Chaplain is usually given the final authority in these matters.

  Correct Answer: C

  The law has generally recognized that the parents do not necessarily exercise autonomy appropriately on behalf of their child. It also recognizes that children cannot exercise autonomy for themselves, and that children should not be required to make complicated decisions about their own care. For children, and for adults who are unable to make medical decisions, a surrogate decision maker is normally named by a court of appropriate jurisdiction.

• Question 400:

  A 30-year-old asymptomatic male presents to your office because his father just had a heart attack. He is concerned that he may have inherited his father's condition because a cholesterol level test done at his work site last year was 220 mg/dL. You review his history and find that he smokes 25 cigarettes a day, eats mostly at fast food restaurants, sits at a desk job, and has no regular moderate intensity physical activities. His blood pressure is 130/85 mmHg and his body mass index (BMI) is 26. Which of the following is the most effective step to successfully help the patient quit smoking?

  A. smoking cessation counseling sessions

  B. nicotine patches

  C. bupropion hydrochloride

  D. physician recommendation to stop smoking

  E. identifying social supports to help in his cessation attempts

  Correct Answer: C

  Whereas all of the interventions have a positive effect on smoking cessation, the bupropion hydrochloride has the greatest effect at 6-month follow-up.