USMLE USMLE-STEP-3 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 331:

  A pregnant woman presents to the ER at 20 weeks' gestation with an acute exacerbation of her chronic bronchial asthma. She complains of a cold of 1 week's duration and admits that she lost her inhaler 2 weeks ago. Her examination reveals a temperature of 38 C, RR of 40, pulse of 110, and fetal heart rate of 150. Her lung examination is notable for diffuse expiratory wheezes and a prolonged I:E ratio. She is utilizing accessory muscles for breathing, which appears labored. Which of the following statements regarding asthma in pregnancy is true?

  A. Asthma exacerbations are more common in pregnant women than in nonpregnant women of similar age.
  B. Influenza vaccination is contraindicated in pregnancy.
  C. Peak expiratory flow rate monitoring is unreliable for monitoring disease state during pregnancy.
  D. In pregnant women, the arterial partial pressure of carbon dioxide (PaCO2) is decreased on arterial blood gases compared to nonpregnant individuals.
  E. Due to potential risks of fetal radiation exposure, chest radiography should not be performed to evaluate for underlying pneumonia in women with asthma exacerbation.
  D. In pregnant women, the arterial partial pressure of carbon dioxide (PaCO2) is decreased on arterial blood gases compared to nonpregnant individuals.

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  Explanation

  Physiologic changes in respiration during pregnancy include reduced total lung capacity and functional residual capacity, increased inspiratory capacity and no change in the vital capacity. Increased progesterone causes a chronic hyperventilation, as reflected by a 3040% increase in tidal volume and minute ventilation. This rise in minute ventilation results in a decrease in both alveolar and arterial carbon dioxide, with normal arterial partial pressure of carbon dioxide in pregnancy ranging between 27 and 32 mmHg. Overall, the risk of asthma exacerbation is not thought to be higher in pregnancy. The peak expiratory flow rate correlates well with the forced expiratory volume in 1 second, which is an excellent way of monitoring disease state in both pregnant and nonpregnant individuals. The Centers for Disease Control recommends vaccination against influenza during the appropriate season for all pregnant women who will be in the second and third trimester during the time of vaccine administration. This is a killed virus vaccine and has not been demonstrated to be associated with risk to the developing fetus. Similarly, the pelvic radiation dose of a single chest radiograph is approximately 50 mrad, which is well below the threshold of concern for fetal risk of 5 rad.

• Question 332:

  A19-year-old male who moved to your city 3 months ago comes to your office complaining of dry cough for the past 23 months. Along with the cough, he has had some shortness of breath with exertion. He denies fever, chills, nausea, vomiting, wheezing, and sneezing. The cough occurs mostly in the morning and improves as the day goes on. He denies similar complaints in the past and has no history of allergies. He says that his father had eczema and an allergy to eggs. You order a CXR. Which of the following are you most likely to find?

  A. normal
  B. diffuse pulmonary congestion
  C. increased bronchial wall markings
  D. cardiomegaly
  E. flattening of the diaphragms
  A. normal

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  Explanation

  This patient is manifesting symptoms consistent with asthma. With the history of recently moving to a new area, along with a family history of allergies and eczema, his asthma may be further classified as allergic asthma. Episodic symptoms of cough, dyspnea, and wheezing are likely to occur. The diagnosis of asthma is made by demonstrating reversible airway obstruction. Airway obstruction is likely to be manifested by a reduction in the FEV1. An increase in the FEV1 of 15% after the use of a bronchodilator is the definition of reversibility. A CXR is most likely to be normal. Numerous cardiac conditions, such as CHF, cardiomyopathies, or pericardial effusions, may result in cardiomegaly on a CXR. Diffuse infiltrates may be seen with infections, interstitial lung disease, or other conditions. Flattened diaphragms would be consistent with prolonged obstructive lung disease, such as emphysema. The treatment of choice for the prevention of symptoms in all stages of asthma other than mild intermittent is inhaled steroid. All patients with asthma should also have a short-acting bronchodilator for acute symptomatic relief. A leukotriene modifier would be an alternative recommendation and might be a good addition to an inhaled steroid, as they also have FDA indications for patients with allergic rhinitis.

• Question 333:

  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%
  D. 36%

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  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 334:

  A25-year-old woman returns for her well-baby check 1 week after delivery. The baby has been gaining weight adequately and awakens several times per night to breast feed. Although the mother claims she enjoys being a mom overall, she looks sad and does reluctantly admit to feeling "down" quite a bit. While she feels a great deal of support by her husband, she finds herself crying when alone. Her sleep is erratic, and she often feels tired, but she is eating adequately. She denies significant guilt or any thoughts of suicide or infanticide. What is the appropriate treatment approach for this patient?

  A. antidepressant
  B. hospitalization
  C. mood stabilizer
  D. psychotherapy
  E. reassurance
  E. reassurance

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  Explanation

  Explanations:

  This woman is likely suffering from "baby blues," which is considered a normal reaction to the stress of the postpartum period. It occurs in up to 50% of women after delivery, usually beginning within several days. It is very important to distinguish this from a major depressive episode, postpartum onset, which requires antidepressant treatment and/or psychotherapy. Hospitalization would be indicated only if there were concerns over suicide, or, in cases of "postpartum psychosis," where psychotic symptoms put the infant in immediate danger. Mood stabilizers would be appropriate if the mood disorder were considered to be a bipolar illness. Baby blues are usually self-limiting and respond to reassurance and support.

• Question 335:

  A 58-year-old male presents to your office for a well-male examination. It has been several years since he last visited a doctor, but he states that he has been in "excellent health." He denies any history of drinking, smoking, or using illegal drugs. He maintains a diet low in sodium and fat. An avid sports enthusiast, he also spends at least 2 hours per day engaged in some type of outdoor physical activity. On physical examination, you discover a translucent waxy papule with raised borders on the posterior aspect of his left shoulder.

  The treatment modality associated with the lowest recurrence rate is which of these?

  A. radiation therapy
  B. Mohs micrographic surgery
  C. surgical excision
  D. electrodesiccation with curettage
  E. cryotherapy
  B. Mohs micrographic surgery

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  Explanation

  Nonmelanoma skin cancer is the most common cancer in the United States. Of this group of cancers, approximately 7080% are basal cell carcinomas (BCC). The majority of the remaining 2030% are squamous cell carcinomas (SCC). Metastasis is less common in BCC than SCC, with an estimated risk for metastasis of less than 0.1%. There is no evidence that total body skin examination reduces morbidity or mortality associated with BCC. The cure rate of BCC ranges anywhere from 80 to 99% depending on the treatment modality employed. Despite adequate treatment, individuals with a prior BCC lesion are at increased risk for development of a subsequent BCC (with a 40% risk of development 35 years after treatment).

  The most important risk factor for development of BCC is exposure to UVB (or shortwavelength ultraviolet) radiation. There is some evidence, however, that UVA (or longwavelength ultraviolet) radiation also confers a risk. Sporadic, intense episodes of sun exposure, particularly during childhood, are associated with increased risk of BCC development later in life. Conversely, SCC is apparently associated with cumulative sun exposure, regardless of intensity. Other risk factors implicated in BCC development include arsenic exposure, immunosuppression, exposure to other forms of radiation, and the presence of other skin- affecting conditions such as xeroderma pigmentosum and basal cell nevus syndrome.

• Question 336:

  A 45-year-old male with type II diabetes, hypertension, and hyperlipidemia presents to your clinic as a new patient. He has been out of his cholesterol medications and came to your office requesting a refill. The patient brought his most recent lipid profile (done after he was off his cholesterol medication for 3 months) which revealed:

  Cholesterol (total): 242 mg/dL HDL cholesterol: 38 mg/dL Triglycerides (TGs): 660 mg/dL LDL cholesterol = unable to calculate due to high TGs He also had recent liver function tests that were normal. Based on Adult Treatment Panel (ATP) III guidelines, which of the following medications should be the initial pharmacologic treatment for this patient?

  A. atorvostatin
  B. gemfibrozil
  C. cholestyramine
  D. omega-3 fatty acids
  E. nicotinic acid
  B. gemfibrozil

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  Explanation

  According to the Third Report of the National Cholesterol Education Program (NCEP) on the ATP III once the TG levels are in very high range (>500 mg/dL) the focus changes from LDL to reducing TGs, as such high levels can trigger acute pancreatitis. Once the LDL is lower than 500 mg/dL, the attention can be turned toward lowering LDL for CHD reduction. The results of various recent meta-analyses revealed that elevated TGs are also an independent risk factor for CHD. Some factors that may lead to elevated TG include obesity, physical inactivity, tobacco use, alcohol use, high carbohydrate diets, diabetes, chronic kidney disease, familial disorders, and certain drugs. ATP III adopts the following classification for serum TGs:

  ?Normal TGs:<;150 mg/dL ?Borderline-high TGs: 150199 mg/dL ?High TGs: 200499 mg/dL ?Very high TGs: 500 mg/dL Nicotinic acid and fibrates have the largest reduction in TG (2530% and 3550%, respectively) and are thus the first-line recommendations in addition to diet modification and exercise in cases of very high TG. Statins reduce TG by roughly 1033%, while bile acid sequestrant can have no effect or even increase TG levels. Fish oils in high doses can be used in recalcitrant cases as they may reduce TG by up to 50%; however GI side effects are common. It is also important to note that active omega-3 fatty acids make up only 3050% of many fish oil supplements, whereas Omacor has 90% omega-3 fatty acids. Although this class of agents can reduce TG effectively, they have the unwanted effect of elevating LDL-C levels.

• Question 337:

  While in the emergency department you see a 3-week-old infant. The mother says that the child felt warm earlier in the day and has not been eating very well. The infant has a temperature of 100.9 and has mildly decreased tone. What is the most appropriate initial management?

  A. Give acetaminophen and reassess in a few hours.
  B. Draw a blood culture, recommend increased fluid intake, and follow-up for re-examination in 24 hours in the primary pediatrician's office.
  C. Admit to the hospital and perform a full "sepsis workup."
  D. Draw a blood culture, give a shot of ceftriaxone (Rocephin) to cover for any infections and follow- up in 2448 hours.
  E. Get a urine culture and begin trimethoprim/sulfamethoxazole (Septra).
  C. Admit to the hospital and perform a full "sepsis workup."

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  Explanation

  A fever in the first 46 weeks of life needs to be treated very aggressively. There are no reliable clinical or laboratory findings currently available that can discriminate between a nominal viral illness and a serious bacterial infection. In the newborn period, fever may be the only indicator of bacteremia or meningitis. Any rectal temperature greater than 100.5 should trig ger a full sepsis workup. This should include cultures of the blood, urine, and spinal fluid. In this age range, empiric antimicrobials should be initiated that should cover for GBS, E. coli, and Listeria monocytogenes. A commonly used regimen is ampicillin and gentamicin. Many would also include empiric acyclovir in this age range. In infants, the routine use of antipyretics should be discouraged. A blood culture alone is not an adequate screening tool for meningitis. While a urinary tract infection (UTI) is a common cause of infection in infants, a more complete evaluation would be warranted.

• Question 338:

  You are called to see a newborn in the nursery because the nurse is concerned that the baby may have Down syndrome.

  What is the most common central nervous system (CNS) complication of Down syndrome?

  A. seizures
  B. hydrocephalus
  C. microcalcifications
  D. berry aneurysms
  E. mental retardation
  E. mental retardation

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  Explanation

  The most common finding in a newborn with Down syndrome is hypotonia. Other common findings include single palmar crease, flat facial profile, macroglossia, and wide space between the first and second toes. Hypotonia in the newborn period should prompt close evaluation and follow-up. Caf?au lait spots are associated with neurofibromatosis. High arched palates are associated with fragile X syndrome.

  Ambiguous genitalia are commonly seen in CAH.

  Children with Down syndrome are at an increased risk for hypothyroidism. It may be hard to detect without routine laboratory screening as they will commonly have mental retardation and developmental delay as part of their syndrome. Hypothyroidism may not be present in the immediate newborn period and requires, at a minimum, annual testing throughout the child's life. The other findings listed are not specifically associated with Down syndrome. Lens dislocation is commonly found with Marfan syndrome or homocysteinuria.

  Children with Down syndrome have an increased prevalence of duodenal atresia. Pyloric stenosis is uncommon to see in the newborn period. It tends to present with nonbilious vomiting usually after 24 weeks of age. Hirschsprung disease (aganglionosis coli) presents with constipation and failure to pass stool. Infants with Hirschsprung disease commonly will not pass stool in the first days of life. Biliary atresia is a progressive cause of jaundice in an infant. It is the most common cause of a cholestatic jaundice in the newborn period. Emesis is not typically associated with biliary atresia. Milk protein allergy is a common cause of bloody stools in the first few months of life, but does not have bilious emesis associated with it.

• Question 339:

  A 55-year-old lawyer without past psychiatric history presents to her internist with complaints of insomnia. Since her husband suddenly passed away 5 weeks ago, she has had difficulty sleeping, frequently awakening throughout the evening. She subsequently finds herself tired during the day. When asked about her mood, she states that she is "sad" and will often break down in tears when thinking about her husband. Although she feels that her job occupies her mind, she describes being distracted and making minor mistakes at work. Her appetite has diminished, but her weight has not changed. While she feels "lost" and that her life is not enjoyable without him, she denies any suicidal ideation. She reluctantly admits to occasionally hearing her husband calling her name at nighttime. She understands that it is not real but still finds it comforting for her.

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

  A. hospitalize her for further evaluation and treatment
  B. initiate treatment with an antidepressant alone
  C. initiate treatment with an antidepressant and antipsychotic
  D. monitor her symptoms over the next several weeks
  E. refer her to a psychiatrist for medication management
  D. monitor her symptoms over the next several weeks

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  Explanation

  This is a woman who is suffering from bereavement, which is not a diagnosable mental illness. Bereavement is considered to be a normal grief reaction to the death of a loved one. Hospitalization would only be indicated if the patient were imminently dangerous to herself (or others) or if she were unable to take care of herself. As she is not suicidal and is functioning adequately at work, hospitalization would be neither necessary nor helpful. Beginning an antidepressant would be appropriate if treating major depressive disorder. While she exhibits some symptoms consistent with MDD, it has been less than 2 months since the sudden death of her spouse and her complaints are not as pervasive as those seen in MDD (DSM IV-TR). Another factor favoring bereavement over major depressive disorder in this patient is the lack of a prior history of depression or current suicidality. Pharmacotherapy with both an antidepressant plus antipsychotic would be the treatment of choice if she were suffering from major depressive disorder with psychotic features.

  Although she does have occasional perceptual disturbances, this phenomenon is not unusual in uncomplicated bereavement. Her insight and lack of other psychotic symptoms, such as delusions or disorganization, are not consistent with a major psychotic illness. Individuals with bereavement do not usually require referral to a psychiatrist unless there is another existing mental disorder or complicating problem. Given the time-limited nature of bereavement, monitoring her symptoms over time is the most appropriate approach for this patient. Referral to grief therapy, either individual or group, may also be helpful. If the patient's symptoms worsen, persist for more than 8 weeks, impair her ability to function, or cause her to be dangerous, then referral to a psychiatrist or hospitalization may be warranted.

• Question 340:

  You are called to see a newborn in the nursery because the nurse is concerned that the baby may have Down syndrome.

  After confirming that the child does indeed have Down syndrome, the parents ask you what problems their baby may have in the future. With which of the following is the infant most likely to have problems?

  A. renal failure
  B. hypothyroidism
  C. osteoporosis
  D. hemophilia
  E. lens dislocation
  B. hypothyroidism

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  Explanation

  The most common finding in a newborn with Down syndrome is hypotonia. Other common findings include single palmar crease, flat facial profile, macroglossia, and wide space between the first and second toes. Hypotonia in the newborn period should prompt close evaluation and follow-up. Caf?au lait spots are associated with neurofibromatosis. High arched palates are associated with fragile X syndrome.

  Ambiguous genitalia are commonly seen in CAH.

  Children with Down syndrome are at an increased risk for hypothyroidism. It may be hard to detect without routine laboratory screening as they will commonly have mental retardation and developmental delay as part of their syndrome. Hypothyroidism may not be present in the immediate newborn period and requires, at a minimum, annual testing throughout the child's life. The other findings listed are not specifically associated with Down syndrome. Lens dislocation is commonly found with Marfan syndrome or homocysteinuria.

  Children with Down syndrome have an increased prevalence of duodenal atresia. Pyloric stenosis is uncommon to see in the newborn period. It tends to present with nonbilious vomiting usually after 24 weeks of age. Hirschsprung disease (aganglionosis coli) presents with constipation and failure to pass stool. Infants with Hirschsprung disease commonly will not pass stool in the first days of life. Biliary atresia is a progressive cause of jaundice in an infant. It is the most common cause of a cholestatic jaundice in the newborn period. Emesis is not typically associated with biliary atresia. Milk protein allergy is a common cause of bloody stools in the first few months of life, but does not have bilious emesis associated with it.