USMLE USMLE-STEP-2 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 321:

  From the below the clinical indications, choose an option for use of immune globulin (IG) in Hepatitis A prophylaxis

  A. indicated
  B. not proven effective
  C. not routinely indicated
  D. contraindicated
  E. compulsory
  A. indicated

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  Explanation

  IG given before exposure or within 14 days of exposure is 7585% effective in preventing symptomatic illness from hepatitis A. IG is produced from the plasma of normal adults and does not contain sufficient antibody to prevent hepatitis B infection. Hepatitis B immune globulin (HBIG) is prepared from plasma known to contain high antibody titers for hepatitis B surface antigen (HBsAg) and is specific for hepatitis B. Given immediately postexposure, and again 1 month later, it has a combined efficacy of about 75% in the prevention of hepatitis B. Postexposure IG has not been found effective in the prevention of hepatitis C infection; on the other hand, treatment of early hepatitis C infection is possible, and thus it is important to monitor exposed individuals to determine whether infection occurs. IG administered to individuals exposed to measles infection who are susceptible to the disease has been shown to be effective if given within 6 days of exposure.

  Recent use of IG is a contraindication to immunization with rubella vaccine. IG is not very effective at preventing in utero infection with rubella, and infants with congenital rubella syndrome have been born to women given IG shortly after exposure. IG is not routinely indicated, as it is indicated only if abortion is not elected.

• Question 322:

  The USPSTF made recommendations for screening mammography and clinical breast examination every 12 years for women aged 40 years and older. Which of the following is the best explanation for why routine screening mammography was not recommended for women in the general population under 40 years of age?

  A. Screening mammography in women less than 40 is not as sensitive as in those over 40.
  B. Screening mammography in women less than 40 is more difficult due to tissue density.
  C. Women under the age of 40 are still likely to have high estrogen levels.
  D. Breast self-examination in the younger group is more sensitive in detecting cancers than mammography.
  E. The benefit of detecting cancers in the younger age group was outweighed by the risks screening caused in that age group.
  E. The benefit of detecting cancers in the younger age group was outweighed by the risks screening caused in that age group.

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  Explanation

  It is true that mammography for detection of breast cancer in older women is technically easier and probably more sensitive than in younger women. However, the burden of cost and mortality resulting from screening women less than 40 was the real reason that screening them was not recommended. For first mammograms of women aged 4049, cancers were diagnosed at half the rate of women aged 50 59 years old, yet twice as many follow-up diagnostic tests were performed. Simply put, the cost in terms of dollars, mortality from testing, and mortality from radiation exposure for women under 40 were not considered to be worth the benefit.

• Question 323:

  A woman at 31 weeks' gestation complains of feeling dizzy and lightheaded when she lies on her back. She is Rh negative but denies vaginal bleeding, abdominal trauma, or abdominal pain. The diagnosis is probably the supine hypotensive syndrome.

  This results in which of the following?

  A. a decreased fetal heart rate
  B. an increased frequency of uterine contractions
  C. a decreased tolerance to pain
  D. a decreased effect of epidural analgesia
  E. an increased risk of placental abruption
  A. a decreased fetal heart rate

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  Explanation

  In late pregnancy, the large uterus commonly compresses the inferior vena cava and impedes return of blood from the lower extremities to the heart. This may be sufficient to reduce cardiac output. In approximately 10% of women, arterial hypotension occurs, which can result in diminished uteroplacental blood flow and a decreased fetal heart rate. None of the other options occur as a result of this syndrome. Management is to have the woman roll on to her side or lean forward if she is sitting. Both these maneuvers cause the uterus to fall away from the inferior vena cava.

• Question 324:

  For each clinical setting described below, select the set of ABG determinations with which it is most likely to be associated.

  A 60-year-old man with morbid obesity

  pH PaO2 PaCO2

  A. 7.23 64 80
  B. 7.39 88 40
  C. 7.22 74 33
  D. 7.54 75 24
  E. 7.37 67 52
  E. 7.37 67 52

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  Explanation

  ABG determinations are essential in the diagnosis of respiratory and acid-based disturbances. Extremely obese patients suffer from increased work of breathing, as well as elevation of the diaphragm with decrease in lung volume. The resultant hypoventilation is characterized by carbon dioxide retention leading to chronic respiratory acidosis with metabolic compensation (ABG set E in the question). When associated with somnolence, excessive appetite, and polycythemia, this is known as the pickwickian syndrome. Modest weight loss can lead to dramatic improvement in respiratory functioning. The earliest derangement in salicylate poisoning is hyperventilation, resulting in decreased PaCO2 and increased arterial pH (ABG set D). Eventually, there is CNS depression with somnolence and hypoventilation resulting in respiratory acidosis. Diabetic ketoacidosis may cause acute metabolic acidosis. In a healthy young adult with no lung disease, appropriate respiratory compensation occurs (ABG set C). Without insulin to reverse this process, the patient may go on to develop worsening acidosis and an inability to compensate adequately. ABG set A reflects acute respiratory acidosis (hypoventilation) without metabolic compensation. ABG set B is normal.

• Question 325:

  A 7-year-old child is scheduled for an elective tonsillectomy. The most important instruction to the parents should be to make sure that the child does which of the following?

  A. avoids contact with other children
  B. discontinues antibiotics 72 hour before surgery
  C. avoids aspirin and antihistamines for 2 weeks before surgery
  D. does not drink from siblings' cups
  E. eats iron-laden foods for 3 weeks before surgery
  C. avoids aspirin and antihistamines for 2 weeks before surgery

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  Explanation

  Aspirin and antihistamines have been shown to adversely affect platelet aggregation, leading to increased bleeding time. Moreover, this effect may persist for 710 days after discontinuing these medications. When possible, children undergoing surgery should not be receiving aspirin or antihistamines. The use of antibiotics would not be a contraindication to elective surgery. Children undergoing elective surgery should be free of respiratory infection. It is prudent to counsel the parents in ways to minimize infection, but avoiding social contacts and shared eating utensils would likely have little effect in the case described in the question. A child should be free of anemia before elective surgery, but eating iron-rich foods would not significantly elevate Hb in a short period of time.

• Question 326:

  For each organism causing food-related illness, choose the corresponding average incubation period.

  What is the average incubation period of C. botulinum?

  A. under 4 hours
  B. 824 hours
  C. 1236 hours
  D. 12 hours to 6 days
  E. 13 weeks
  D. 12 hours to 6 days

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  Explanation

  Knowing the incubation period (average and range) of a pathogen can be important in determining the source of infection in food-borne disease. Knowing what food was eaten on the day of an attack of food poisoning may not help in establishing C. botulinum as the cause of illness, since certain strains of S. aureus cause food-borne disease by the production of enterotoxin. As no time is required after ingestion for the growth of colonies in the infected host, and the toxin affects the vagus nerve in the stomach, the incubation period is under 4 hours. C. perfringens, formerly known as Clostridium welchii, causes food- borne disease, after 824 hours when enterotoxin is released when C. perfringens passes from stomach to intestine. Meat prepared in bulk for consumption at a banquet or in an institution is a possible source. Spores that survive incomplete cooking may start reproducing during cooling and may persist if subsequent rewarming is not completed to a temperature above 60°C (140°F) required to kill the organisms. Salmonella has an incubation time of 1236 hours. It may also survive in meat and other products if cooking is inadequate and heat does not penetrate below the surface of the food. The organisms multiply in the gut of the infected host, and low infective doses may therefore have longer incubation periods

• Question 327:

  A 70-year-old man is brought to his primary care doctor by the man's son. According to his son, who had not seen his father for about a year, the father seemed to have some personality changes. He was no longer interested in his hobbies and seemed apathetic. He seemed to forget easily, and he repeatedly asked the same already answered questions. On at least two occasions, the father wandered out of the house and was found by neighbors, who thought he was confused. Which of the following is the most common cause of dementia in a 70-year-old man?

  A. Alzheimer's disease
  B. Pick's disease
  C. Parkinson's disease
  D. vascular dementia
  E. subcortical dementia
  A. Alzheimer's disease

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  Explanation

  Alzheimer's disease is the most common form of dementia. Of persons with dementia, 5060% will have Alzheimer's. Vascular dementia is the second most common, accounting for about 1530% of dementias.

• Question 328:

  Select the ONE best lettered option that is the most likely diagnosis of vaginal bleeding in pregnancy. Each lettered option may be selected once, more than once, or not at all.

  A 23-year-old pregnant woman at 16 weeks' gestation begins to have light vaginal bleeding several hours after sexual intercourse. She has no abdominal discomfort. Her prenatal course has been uneventful and fetal heart tones were heard at 12 weeks. Her uterus is midway between her symphysis pubis and umbilicus, and is soft and nontender. Fetal heart tones are now 148 BPM. Her cervix is undilated.

  A. threatened abortion
  B. gestational trophoblastic disease
  C. cervicitis
  D. placenta previa
  E. placental abruption
  F. uterine rupture
  G. placenta accreta
  H. uterine inversion
  I. uterine atony
  J. vaginal lacerationK. tubal pregnancy
  C. cervicitis

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  Explanation

  Light vaginal bleeding following sexual intercourse is likely of cervical origin because of the increased blood flow to the pelvic organs in pregnancy and eversion of the endocervix that occurs as a result of the increased estrogen production. The absence of abdominal pain and tenderness, the appropriate size of the uterus and the spotting rather than overt bleeding tend to exclude threatened abortion as the cause of this woman's bleeding.

• Question 329:

  A 25-year-old Caucasian man reports that he has got in trouble with the law as a result of his rubbing up against a woman he did not know in an elevator at work. Recurrent, intense sexually arousing fantasies, sexual urges, or behaviors involving touching and rubbing against a nonconsenting person, such as a stranger in an elevator, which occur for at least 6 months and which cause significant impairment in an individual's functioning are best characterized as which of the following?

  A. exhibitionism
  B. fetishism
  C. frotteurism
  D. pedophilia
  E. sexual masochism
  C. frotteurism

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  Explanation

  Frotteurism is the term given to obtaining sexual gratification by rubbing. It is usually the only source of sexual gratification for the man involved, who rubs his penis against the buttocks or other bodily part of a fully clothed woman to achieve orgasm. Exhibitionism is the exposure of one's genitals to an unsuspecting person. Fetishism is the term for intense sexual fantasies and behaviors involving the use of nonliving objects, such as female undergarments. Pedophilia is the term for intense sexual urges toward children 13 years of age or younger, and sexual masochism is the term for sexual arousal involving the real act of being humiliated, beaten, bound, or otherwise made to suffer.

• Question 330:

  A55-year-old man presents to the physician's office for his yearly physical examination. He is asymptomatic. Past history is pertinent for hypertension. Family history is positive for breast cancer in his mother at age 70 and colon cancer in his father at age 65. His examination is unremarkable except for guiac positive stool. Barium enema shows a sigmoid colon polyp. Colonoscopy confirms a 3-cm pedunculated polyp in the sigmoid colon, and snare polypectomy is performed. Pathologic examination reveals an adenomatous polyp with a focus of invasive carcinoma in the head, with a 4-mm resection margin and no tumor noted in the stalk.

  Which of the following is the most appropriate next step in management?

  A. CT scan
  B. magnetic resonance imaging (MRI) scan
  C. surgical resection of sigmoid
  D. observation
  E. regular use of nonsteroidal anti-inflammatory drugs (NSAIDs)
  D. observation

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  Explanation

  The prevalence of adenomas without symptoms in patients over the age of 50 ranges between 20 and 40% . Screening studies suggest that 30% of patients without symptoms over the age of 50 who undergo colonoscopy for evaluation of positive fecal occult blood have a polyp detected. Polyps greater than 2 cm have a high potential for malignant degeneration. The polyp should be completely removed, preferably by snare polypectomy. Most studies indicate that polypectomy is adequate for polyps with carcinoma in the head if the margin of resection is 2 mm or greater, especially if the stalk is not invaded. Following adequate polypectomy, observation would be indicated with postpolypectomy colonoscopic surveillance. If cancer is present at or near the margin, then colon resection is indicated. Because the incidence of residual cancer and metastatic disease is very low after successful polypectomy, scanning by CT or MRI is not indicated.

  The data on NSAID use are promising but insufficient to support a clinical recommendation.