USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 301:

  The mortality rates from two countries are being compared. Despite vast differences in wealth, level of public services, birth rates, and education, the difference in crude mortality rate is the opposite of what is expected: The more developed country has the higher crude mortality rate. Which of the following should you do to better understand this difference?

  A. Verify a difference in health status of residents by doing a health survey.

  B. Examine the causes of death to determine the reason for the difference.

  C. Recalculate the rates using 5-year aggregate data.

  D. Calculate an age-standardized death rate for each country.

  E. Compare the mortality rates for cities of equal size in each country.

  Correct Answer: D

  Crude mortality rates for a population are calculated using total deaths divided by total population. Differences in the age compositon of the population can make an enormous difference in crude mortality rates, since the elderly have a much higher mortality rate. Adjusting for age computes a hypothetical "adjusted" rate for each country based on their own age-specific mortality rates, but using standard population. The technique is called age adjusting, or standardization. It is used in other rate studies as well. For instance, the crude mortality rates for MI would be different for a largely middle- aged population than for an older population. Age adjusting allows comparison.

• Question 302:

  Afamily is scheduled to move into a home that is 15 years old. Its water supply is a well, and sewage is discharged to an on-site septic system. In preparation for the move, they obtain a series of water tests from the well. All of the results show the presence of coliform bacteria.Which of the following is the implication of these data?

  A. They are at risk of acquiring a coliform bacterial infection.

  B. The well water has been mixed with untreated surface or groundwater.

  C. Nothing--this is a common finding in the country.

  D. The groundwater is extensively contaminated and the house is unlivable.

  E. They can live in the house but must seek medical care at the first sign of illness.

  Correct Answer: B

  Testing for the presence of coliform bacteria is a standard bacterial test of water quality. Since coliform bacteria are ubiquitous in nature, their presence means only that the water has been contaminated with water from the ground surface or the septic system. It is only an indicator. Coliform bacteria are not the principal agents of disease. It is the other agents introduced into the water by the contamination that create the risk. The problem should be resolved before using the well water. A common cause of contamination is poor well construction, resulting in surface water moving down the outside of the well casing and into the water source.

• Question 303:

  An outbreak of influenza occurs across the United States in the early winter. Of individuals contracting influenza, a large proportion had received vaccinations earlier in the fall. Which of the following is the most likely explanation?

  A. The vaccine was manufactured improperly.

  B. The vaccine used did not contain antigen specific to the outbreak strain.

  C. A systemic storage problem with a major shipper damaged the vaccine.

  D. Due to unusually cold weather, people were more susceptible.

  E. The virus was especially virulent.

  Correct Answer: B

  Manufacturing, storage, and shipping problems do occur. However, they have not been related to nationwide failures, although a major manufacturing problem in 2004 resulted in a major reduction in supply of vaccine. It is more likely that the vaccine in use is not completely protective against the prevalent viral strain. The WHO monitors influenza outbreaks worldwide. Based on strains present in outbreaks, and especially in the Pacific Rim, WHO makes a recommendation every spring regarding the antigens to use for the fall immunization campaign. Manufacturing then begins. Although their track record is good in this regard, antigen changes in influenza may reach the United States undetected or ahead of schedule

• Question 304:

  A young child finds a bat lying on the floor of his room. The child picks it up to show it to his mother, and it bites him on the hand. The bat then escapes, flying out of an open window. Which of the following diseases poses the most serious threat to the child's health?

  A. rabies

  B. lacrosse encephalitis

  C. distemper

  D. tularemia E. tetanus

  Correct Answer: A

  Transmission of rabies virus by a bat bite has been well documented, and in many areas of the country, bats are known to harbor the rabies virus. There are also well-documented cases of human rabies due to viral strains found in bats, but without a good history of being bitten. Therefore, presumptive treatment is recommended in the case of a bite (and in some cases for a possible bite) when the bat cannot be recovered and tested. Lacrosse encephalitis, distemper, and tularemia are not known to be transmitted by bats. Tetanus is unlikely because a child this age has probably been immunized.

• Question 305:

  You see a young mother whose child is in need of medical care. She has an income below the federal poverty level. She is eligible to receive cash payments under the Supplemental Security Income Program (SSI). As she has no health insurance, you ask a social worker to help her enroll in a program funded with state and federal tax dollars, which provides complete medical care for her child. You ask that she be enrolled in which of the following programs?

  A. Medicaid

  B. Medicare

  C. Blue Cross/Blue Shield

  D. The Robert Wood Johnson Foundation

  E. Women, Infants, and Children program (WIC)

  Correct Answer: A

  Medicaid and Medicare began under federal legislation in 1966. Medicaid is a state-run program funded with federal and state tax dollars. It was established to provide medical services to the poor, with special consideration to pregnant women and small children. Although eligibility varies greatly from state to state, persons who receive SSI welfare payments are categorically eligible. Medicare is a federal program, completely financed and run by the federal government. Its purpose is to provide medical care to citizens over 65. Blue Cross/Blue Shield is a private insurance that must be purchased; the Robert Wood Johnson Foundation is a large foundation that provides grants; and the WIC program is a food supplement program for needy mothers and children.

• Question 306:

  You assume care of a 28-year-old nursing home aide, who recently had a positive tuberculin skin test (TST). In the past, her tests have always been read as negative; this year, she developed a 20. 25 mm induration. She feels well and has no cough. Abaseline white blood cell count and liver function test is normal, and a recent HIV antibody test is negative. You order a chest x-ray, which is normal. Which of the following is the best next step in management?

  A. Begin three-drug antituberculosis therapy.

  B. Educate the patient on the symptoms of tuberculosis and repeat the chest x-ray in 1 month.

  C. Isolate her from her family and other close contacts.

  D. Immunize the patient with bacillus Calmette-Gu閞in (BCG) vaccine.

  E. Begin isoniazid, 300 mg daily.

  Correct Answer: E

  The patient has a positive reaction to purified protein derivative (PPD). This indicates tuberculosis infection, but not necessarily clinical disease. Health care workers have a risk of acquiring tuberculosis that is 210 times the risk for the general public. Since conversion is recent (she had a negative test last year), the risk of progressing to disease is relatively large compared to the risk of hepatotoxicity from preventive treatment with isoniazid. Such preventive treatment is 6580% effective in preventing progression to active disease. Note that new assays (ELISPOT, QuantiFERON) performed on a blood sample or oral swab are becoming available, and that they are more sensitive and specific for exposure to Mycobacterium tuberculosis than is the TST.

• Question 307:

  You provide health services for employers in your community. The employers explain to you that they appreciate efforts to contain costs because their insurance premiums are experience rated. Which of the following describes why employers are concerned?

  A. An experienced management team has set new rates for the employers.

  B. The employers pay the cost of service as out of pocket expenses.

  C. Everyone in the community pays the same rate for insurance based on community charges and overheads.

  D. The employer pays a large deductible premium.

  E. An employer's rates reflect past utilization by the employer.

  Correct Answer: E

  The insurance company charges premiums to the employer based on "experience rating," which means charges are based on past utilization of service. To control premiums in the future, control utilization now. Community rating would be different, in that risk would be spread across a broader community. Community rating makes insurance more affordable for individuals or groups that use a lot of health care, but removes incentive to control costs.

• Question 308:

  A study finds that the relative risk of stomach cancer after the consumption of a new sugar substitute is 3.5 with a 95% confidence interval of 1.15.3. Which of the following best describes the true relative risk?

  A. If repeated samples are taken from the population, 95% of the time the relative risk will fall between 1.1 and 5.3.

  B. If repeated samples are taken from the population and confidence intervals are found for each sample, 95% of the confidence intervals will include the true population relative risk.

  C. If repeated samples are taken from the population and confidence intervals are found for each sample, 95% of the confidence intervals will fall somewhere between 1.1 and 5.3.

  D. If repeated samples are taken from the population, 95% of the time the true relative risk for the population will fall between 1.1 and 5.3.

  E. Ninety-five percent of individuals from a particular sample will have a relative risk between 1.1 and 5.3.

  Correct Answer: B

  A confidence interval gives an estimated range of values which is likely to include an unknown population parameter, in this case the relative risk of stomach cancer with consumption of the sugar substitute. The estimated range is calculated from a given set of sample data. If independent samples are taken repeatedly from the same population, and a confidence interval calculated for each sample, then a certain percentage of the intervals will include the unknown population parameter.

• Question 309:

  Doing a retrospective chart review of unmatched cases and controls, you calculate an OR to make an initial assessment of whether women who have had induced abortions are more likely to develop breast cancer. Twenty of 100 women with breast cancer reported a history of induced abortion. Ten of 200 women without breast cancer reported a history of induced abortion. What is the OR?

  A. 0.053

  B. 0.11

  C. 2.00

  D. 2.201

  E. 4.716

  Correct Answer: E

  The OR for exposure is calculated by dividing the odds of exposure for cases by the odds of exposure for controls: OR = (20/80)/(10/190) = 4.716. (Note that an unmatched case-control study such as this example would be flawed by confounding [age] and bias [recall bias]. Patients with breast cancer are more likely to remember and report that they had certain exposures compared with those without breast cancer.)

• Question 310:

  A 3-year-old child recovers from a severe episode of bloody diarrhea, hemolysis, and uremia. The child's case is linked to other cases across the country by statistical association with consumption of hamburgers obtained from a nationwide supplier of ground beef. Which of the following is the best method for preventing this illness in the general population?

  A. cooking ground beef to be well done, and thoroughly washing fruits and vegetables

  B. regulations enforcing worker hygiene in the workplace

  C. a testing program for enteric disease in Livestock

  D. regulations enforcing sanitary conditions in slaughterhouses

  E. a ban on imported meats and produce

  Correct Answer: A

  The illness described is consistent with hemolytic uremic syndrome associated with E. coli 0157:H7 infection. E. coli 0157:H7 is the most common strain found of the enterohemorrhagic E. coli (EHEC) group. Although its most common reservoir is thought to be in cattle, it has been found in other livestock. The usual mode of exposure is contamination of beef. The problem is compounded significantly when beef is ground and mixed in bulk. Testing and elimination programs do not appear sensitive enough to eliminate exposure, although active research in the area continues. In addition, there are many other outbreaks associated with fresh vegetables, bean sprouts, and unpasteurized juices. It is hypothesized that these are due to contamination with human or animal waste. Since the organism is killed by heating, thorough cooking of ground beef products, avoidance of contamination of fresh foods with raw meat, and washing of produce intended to be served fresh is the most practical intervention. Currently, this remains the most practical advice to give the public.