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

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 241:

  A 24-year-old woman has a MSAFP of 0.5 MOM (multiples of the median) at 17 weeks' gestation. Which of the following fetal abnormalities is most likely to occur with this MSAFP?

  A. spina bifida
  B. omphalocele
  C. gastroschisis
  D. bladder exstrophy
  E. trisomy 21
  E. trisomy 21

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  Explanation

  Production of AFP begins in the yolk sac and then moves to the fetal liver and, to a lesser extent, the fetal gastrointestinal tract. Choices A. through D. result in an increased maternal serum AFP (MOM greater than 2.0) because all are open defects of the fetus that result in an increase in amniotic fluid concentrations and then maternal serum concentrations of AFP. Trisomy 21 (Down syndrome) is associated with a decreased MSAFP. In clinical practice, measurement of MSAFP is combined with serum chorionic gonadotropin (hCG) and unconjugated estriol (E3). These three tests are commonly called a triple screen or triple marker screen and together improve the sensitivity over each test alone. Approximately 60% of trisomy 21 fetuses in women under age 35 years, and more than 75% in women over 35 will be detected using a multiple marker screening test. Screening for these defects is most sensitive between 16 and 18 gestational weeks, but the test should be offered to all pregnant women between 15 and 22 gestational weeks.

• Question 242:

  A 4-year-old child manifests symptoms of fever, sore throat, and swollen lymph nodes. The spleen tip is palpable. Throat culture and rapid slide (Monospot) test results are negative. The next logical diagnostic procedure would involve which of the following?

  A. rapid streptococcal antigen test
  B. heterophil titer
  C. Epstein-Barr virus (EBV) titer
  D. chest x-ray
  E. bone marrow examination
  C. Epstein-Barr virus (EBV) titer

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  Explanation

  Infectious mononucleosis may affect children of all ages. The rapid slide (Monospot) test response is positive in approximately 90% of infected persons; however, younger children with mononucleosis may have a negative result. Moreover, many younger children have poor antibody response to the heterophil titer test. The specific serodiagnostic test for EBV, the agent responsible for most cases of infectious mononucleosis, confirms the diagnosis. A repeat throat culture, even if positive for betahemolytic Streptococcus, may be of only partial value, because both infectious mononucleosis and streptococcal pharyngitis may be present simultaneously. Bone marrow examinations potentially are painful and contribute little to the correct diagnosis.

• Question 243:

  An 18-month-old girl is brought to the hospital with a history of 6 days of bloody diarrhea. She has been drinking well but has not been wetting her diaper. She has been irritable. On physical examination, she has periorbital edema. She appears pale and is tachycardic. Her CBC shows a hemoglobin of 6 g/dL and a platelet count of 100,000/mm3. Her blood urea nitrogen (BUN) is 50 mg/dL and creatinine is 5.5 mg/dL. Her urinalysis shows gross hematuria. Which of the following is the most likely causative organism for her clinical problem?

  B. group A Streptococci
  C. group B Streptococci (GBS)
  D. S. aureus
  E. the cause of this illness is not known
  A

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  Explanation

  The child most likely has hemolytic-uremic syndrome. This illness is most common in children under 2 years old. They present with a prodromal illness, bloody diarrhea, and then a sudden onset of lethargy and pallor when the hemolytic anemia occurs. Coincident with this is the development of acute renal failure, often with low urine output. E. coli 0157:H7 is the most common organism in the United States. Group A Streptococci are associated with poststreptococcal acute glomerulonephritis.

  Thrombocytopenia and anemia are not seen in this disease.

• Question 244:

  Afamily brings in their 7-year-old boy because he has not been fitting in at school. The mother says he has not made any friends and tends to play mostly by himself. He exhibits repetitive hand flapping. When you interview him, he does not provide any eye contact, and the mother says this is typical for him. His speech seems age appropriate and per history has developed normally. This past year his IQ was tested to be normal.

  Which of the following is the most likely diagnosis?

  A. autism
  B. Asperger disorder
  C. Rett disorder
  D. attention deficit hyperactivity disorder (ADHD)
  E. borderline personality disorder
  B. Asperger disorder

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  Explanation

  Children with Asperger disorder show severe sustained impairment in social interaction, and restricted repetitive patterns of behavior. Unlike autistic disorder, in Asperger disorder language and cognitive development are not delayed. In Rett disorder, a child shows deterioration of developmental milestones, head circumference, and overall growth. In Rett disorder, verbal abilities are usually lost completely.

• Question 245:

  A 39-year-old pregnant woman with chronic hypertension and one prior pregnancy is now at 38 weeks' gestation. She comes to labor and delivery with profuse vaginal bleeding and abdominal pain of sudden onset.

  Which of the following is the most likely diagnosis?

  A. bloody show
  B. vaginal laceration from coitus
  C. cervicitis
  D. placenta previa
  E. placental abruption
  E. placental abruption

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  Explanation

  Painful vaginal bleeding is most likely the result of placental abruption, premature separation of the placenta. Bloody show is a normal sign of impending or early labor. The bleeding is scant and intermingled with clear mucus. Bleeding from a vaginal laceration following coitus is not associated with abdominal pain. A history of coitus followed immediately by bleeding suggests this diagnosis. Bleeding from cervicitis is most often spotting and not associated with abdominal pain. Classically, bleeding with a placenta previa is painless.

• Question 246:

  A shipment of produce is identified as having a higher than allowable level of pesticide. Which of the following regulatory agencies retains the authority to remove the produce from the market?

  A. Food and Drug Administration (FDA)
  B. United States Department of Agriculture (USDA)
  C. Environmental Protection Agency (EPA)
  D. United Nations Food and Agriculture Organization (FAO)
  E. World Health Organization (WHO)
  A. Food and Drug Administration (FDA)

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  Explanation

  In the United States, the organization of food and water control is complex. Among the federal control agencies, the EPA is the most recent, and in many ways the most active and powerful. This agency has now set up an elaborate system of regulation and control of the use of pesticides (which until 1970 was the responsibility of the USDA) and has banned the marketing of chlorphenothane (DDT) for use in the home. The FDA has authority to remove food from the market if it contains pesticides (e.g., PCBs in fish) in excess of the action levels set by the EPA. The FDA also retains the authority to remove from the market any food with inappropriate additives, that contains substances harmful to human health, that is stored in unsanitary conditions, that has decomposed, or that is not fit for consumption.

  The USDAenforces wholesomeness standards that it sets for the production and sale of meat. International control is assisted by the WHO. This agency has mounted control programs for the eradication of communicable disease with conspicuous success in the case of smallpox. It also publishes the International Statistical Classification of Disease (ICD-9).

• Question 247:

  For the screening tests listed below, select the screening schedule that is appropriate for women (as per the U.S. Preventive Services Task Force [USPSTF], The Guide to Clinical Preventive Services, 2006)

  Mammography with or without clinical breast examination

  A. do not routinely screen
  B. yearly over age 50
  C. at first prenatal visit
  D. every 12 years at age 40 and older
  E. every 12 years at age 50 and older
  F. every 3 years following an initial examination, but not after age 65
  G. every 3 years at age 50 and older
  D. every 12 years at age 40 and older

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  Explanation

  The USPSTF recommends that women aged 40 and older have screening mammography with or without clinical breast examination, every 12 years.

• Question 248:

  A 3-year-old boy was bitten while teasing a neighborhood cat. On examination, there are two puncture wounds on the right hand and some superficial scratch marks. There is erythema, warmth, and induration around the puncture sites. Which of the following organisms most likely caused the infection?

  A. Pasturella multicoda
  B. Bartonella henselae
  C. Eikenella corrodens
  D. Peptostreptococcus species
  E. alpha Streptococci
  A. Pasturella multicoda

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  Explanation

  P. multicoda and

  S. aureus are organisms commonly associated with cat bites. The cat's sharp teeth and claws predispose the victim to puncture wounds. Wound infections are more common in cat bites than dog bites.

  E. corrodens, Peptostreptococcus species, and alpha Streptococci are more common with human bites.

  B. henselae causes cat-scratch disease, which presents with subacute lymphadenitis.

• Question 249:

  A 39-year-old pregnant woman with chronic hypertension and one prior pregnancy is now at 38 weeks' gestation. She comes to labor and delivery with profuse vaginal bleeding and abdominal pain of sudden onset.

  If the patient has a placental abruption, which of the following is the most likely risk factor

  A. advanced maternal age
  B. low parity
  C. coitus immediately before the onset of bleeding
  D. hypertension
  E. a step aerobic class immediately before the onset of bleeding
  D. hypertension

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  Explanation

  Maternal hypertension is the most common risk factor for a placental abruption. The relative risk is 3.8 for parous women and 1.6 for nulliparous women. In one published report, half of the women with an abruption severe enough to kill the fetus had hypertension, and half of these had evidence of chronic vascular disease. Advanced maternal age without confounding factors such as diabetes or hypertension is not a risk factor for placental abruption. High parity is associated with an increased risk of placental abruption. Vigorous coitus can cause a vaginal laceration, but not abdominal pain. While blunt abdominal trauma may cause a placental abruption, routine forms of exercise are not a risk factor for placental abruption.

• Question 250:

  A parent brings in a 5-year-old boy being treated for acute lymphocytic leukemia (ALL). He states a friend who is staying with them at their home has just come down with chicken pox. Your patient has not had chicken pox or received immunization with varicella vaccine.

  What is the appropriate treatment?

  A. acyclovir given IV
  B. varicella vaccine
  C. varicella immune globulin (VZIG)
  D. varicella vaccine and VZIG
  E. acyclovir given IV for 7 days, varicella vaccine, and VZIG
  E. acyclovir given IV for 7 days, varicella vaccine, and VZIG

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  Explanation

  Children with chicken pox may be infectious for 1 or 2 days before the appearance of the rash. Once skin lesions have crusted, the patient is no longer infectious. Susceptible individuals can contract chicken pox from patients with zoster. In the cases of both chicken pox and zoster, transmission is thought to occur by the respiratory route rather than by direct contact. The virus can travel long distances in the air and remain viable. Transmission from one hospital patient to other susceptible hospitalized patients has been reported to occur through air vents. VZIG should be given within 3 or 4 days of exposure to varicella-susceptible individuals who are immunocompromised.