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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 421:

  A 55-year-old male is brought to the ED, by ambulance, because of crushing chest pain radiating to his left shoulder and arm that started 1 hour ago. He has a history of hypertension, high cholesterol, and has smoked a pack of cigarettes a day for 30 years. He has never had symptoms like this before. Fortunately, the patient survives this episode. As part of his long-term treatment, which of the following would be an appropriate therapeutic intervention to initiate due to its proven effect on survival rate?

  A. flecainide
  B. captopril
  C. quinidine
  D. digoxin
  E. nitroglycerin
  B. captopril

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  Explanation

  The clinical scenario described is classic for an acute MI. The patient has multiple risk factors, including smoking, hypertension, and elevated cholesterol. His symptoms of crushing chest pain radiating to the left arm is commonly seen in this setting. Often the first electrocardiographic sign of acute ischemia is the development of hyperacute T waves. The ECG will usually show S-T segment elevations in the area of the involved occluded vessel, with reciprocal S-T segment depressions in uninvolved areas.

  This can be followed by the eventual resolution of S-T segment abnormalities and the development of T wave inversions and Q waves. Diffuse P-R depressions are often the initial manifestation of pericarditis, a less common cause of acute chest pain. This often progresses to diffuse S-T segment elevations, the presence of which helps to distinguish pericarditis from the focal S-T elevations more classically associated with a thrombosed coronary artery. Q waves would be unlikely to occur within 1 hour of the onset of symptoms. In this clinical setting, a normal ECG, while possible, would be less likely to occur.

  Ventricular arrhythmias, both tachycardia and fibrillation, are recognized complications of acute MI. The presence of ventricular fibrillation or pulseless ventricular tachycardia should lead to the primary "ABCD" survey, as outlined in the American Heart Association's ACLS protocols. The mnemonic stands for airway, breathing, circulation, and defibrillation. Epinephrine, lidocaine, or amiodarone are reserved for the setting where defibrillation is ineffective. Synchronized cardioversion would be used in efforts to convert a patient's rhythm in the setting of a stable tachycardia.

• Question 422:

  A mother brings her baby girl for a 9-month wellchild visit. You have been following her since birth. Her growth chart is shown in Figure. Her vital signs and examination are otherwise normal. The growth pattern is most consistent with which of the following?

  A. congenital growth hormone (GH) deficiency
  B. constitutional short stature
  C. constitutional growth delay
  D. familial short stature
  E. nutritional failure to thrive (FTT)
  E. nutritional failure to thrive (FTT)

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  Explanation

  This infant's growth pattern is most consistent with nutritional FTT. This is often termed "nonorganic" FTT. This term is used for conditions in which the child, usually an infant, begins to fall off of the standardized growth curves. The growth curve in this vignette shows that this infant's weight has trailed off while her length has remained stable. Causes of poor growth that are hormonal in nature will tend to have blunted growth velocity (decreased linear growth) that results in infants and children with short stature and normal weight. Short stature refers to deceased linear growth (i.e., length or height). The infant in this vignette does not have short stature, as her linear growth is normal. Achild with GH deficiency would be expected to have a decreased linear growth velocity (height) with a weight that remains relatively stable. The next best step in the evaluation of this infant would hinge on understanding the total calories that this infant is consuming. A measure of the appropriate caloric intake is related in terms of calories per kilogram per day. This will give a metric to measure whether infants are getting appropriate nutritional intake. Obtaining a serum GH level is an unreliable way to look at an infant's growth due to its pulsatile nature. While a serum somatomedin- C (ILGF-1) may be a more accurate measure of GH activity, in this child a level will likely not reveal much useful information. In children with malnutrition or caloric deprivation, a somatomedin-C level may be depressed due to decreased body mass. If there were a family history of short stature, that would be manifested with poor linear growth, which is not the case in this vignette. While a malabsorption may be a cause of FTT, an UGI series would not be the modality to evaluate for it.

• Question 423:

  A 50-year-old male presents to your office after reading an article on the Internet stating that a recent study showed that the drug finasteride can prevent prostate cancer. He asks you to prescribe this medication for him. You review the article and find the following information: a randomizedcontrolled trial of men over the age of 55 with normal prostate-specific antigen (PSA) readings was performed comparing finasteride and a placebo. At the end of the study, 18% of the men in the finasteride group and 24% of the men in the placebo group had developed prostate cancer.

  How many men need to be treated with finasteride to prevent one case of prostate cancer (NNT)?

  A. 6
  B. 10
  C. 17
  D. 24
  E. 32
  C. 17

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  Explanation

  Explanations:

  The NNT is calculated by first determining the ARR for a specific outcome between two groups in a study. The ARR, or risk difference, is calculated by subtracting the percentage of subjects who develop an The outcome in the treatment group from the percentage who develop the outcome in the control group. outcome considered is the development of prostate cancer. This occurred in 24% of the control group and 18% of the finasteride group. The ARR is calculated as 24% - 18% = 6% or 0.06. The NNT is calculated as: NNT = 1/ARR. In this example, the NNT = 1/0.06 = 16.67, approximately 17. This suggests that for every 17 men who took finasteride there was one fewer case of prostate cancer. The NNH is calculated in exactly the same manner as the NNT. The only difference is that the outcome is adverse. In this study, highgrade prostate cancers occurred more often in the finasteride group than the placebo group; 6.4% of men who took finasteride and 5.1% who took a placebo developed high-grade prostate cancer. The risk difference, in this case an absolute risk increase, is 6.4% - 5.1% = 1.3% or 0.013.

  The NNH = 1/absolute risk increase = 1/0.013 = 77

• Question 424:

  A62-year-old male on total parenteral nutrition (TPN) for 2 weeks following development of a postoperative enterocutaneous fistula has developed high, spiking temperatures up to 102.2 over the last 8 hours. The only abnormal finding on physical examination is erythema and induration around his central line.

  The most appropriate management is which of the following?

  A. begin broad-spectrum antibiotics and observe for 24 hours
  B. obtain blood cultures through the central line, begin broad-spectrum antibiotics and await culture results
  C. remove catheter, send tip for culture and replace with a new central line over the guide wire
  D. remove catheter, send tip for culture and establish central line at another site
  E. remove catheter, send for culture and establish peripheral intravenous line
  D. remove catheter, send tip for culture and establish central line at another site

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  Explanation

  A high index of suspicion is warranted for catheter sepsis in any patient who has had a central line for several days and suddenly spikes a high fever. The catheter site may have erythema, induration, tenderness, and purulent discharge extruding from the skin. Often, however, the skin appears normal. Athorough search for other possible sources of fever including pulmonary, intra-abdominal, urinary, and wound infections is always prudent. Catheter sepsis can be life threatening and early intervention is essential. Peripheral and central blood cultures should be obtained and the catheter must be removed promptly. It is contraindicated to replace the catheter over a guide wire because the skin tract is infected. It is not mandatory to treat with antibiotics unless the fever persists or signs of sepsis are present.

• Question 425:

  A 17-year-old male presents for evaluation of shortness of breath. He has episodes where he will audibly wheeze and have chest tightness. His symptoms worsen if he tries to exercise, especially when it is cold. He has used an OTC inhaler with good relief of his symptoms, but he finds that his symptoms are worsening. He now has episodes of wheezing on a daily basis and will have nighttime wheezing and coughing, on average, five or six times a month. You suspect a diagnosis of asthma.

  Which of the following is the most appropriate pharmacologic regimen for this patient?

  A. a systemic antihistamine as needed
  B. a short-acting inhaled bronchodilator as needed
  C. a scheduled inhaled steroid and a shortacting inhaled bronchodilator as needed
  D. a scheduled long-acting beta agonist, a scheduled inhaled steroid, and a shortacting inhaled bronchodilator as needed
  E. a systemic corticosteroid, a scheduled inhaled steroid, and a scheduled longacting beta agonist
  D. a scheduled long-acting beta agonist, a scheduled inhaled steroid, and a shortacting inhaled bronchodilator as needed

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  Explanation

  Asthma is a chronic lung disease characterized by inflammation of the airways, causing recurrent symptoms. The characteristic symptoms are wheezing, chest tightness, shortness of breath, or cough. Symptoms often worsen in the face of certain triggers, which include allergens, cold air, exercise, or other irritants. Physical examination may reveal hyperexpansion of the thorax, expiratory wheezing with a prolonged expiratory phase of respiration, and signs of allergies or atopic dermatitis. Asthma can be diagnosed by a history of episodic symptoms of airway obstruction (wheeze, dyspnea, cough, chest tightness), establishing the presence of airflow obstruction that is at least partially reversible and ruling out other causes of these symptoms/signs. Airflow obstruction can be shown by spirometry revealing an FEV1 of <80% predicted or an FEV1/forced vital capacity of <65% of the lower limit of normal. Reversibility can be shown by an FEV1 increase of 15% and at least 200 mL with the use of a short- acting beta agonist. Expiratory wheezing on examination is commonly seen in asthma but is a nonspecific finding. Many patients with asthma have elevated serum IgE levels; it is unusual to find asthma in individuals who have a low level of serum IgE. The sputum of asthmatics may contain eosinophils, Charcot-Leyden crystals, Curschmann spirals, or Creola bodies.

  However, eosinophils may also be present in the sputum of patients with other conditions such as Churg- Strauss syndrome or eosinophilic pneumonia. Peak-flow monitoring is useful for the short- and long-term monitoring of asthma patients and for exacerbation management (by aiding in the determination of exacerbation severity which directs therapeutic decision making). persistent based on the frequency of symptoms and the degree of airflow obstruction. Based on this patient's frequency of symptoms, he falls into the moderate persistent class. An often neglected diagnosis is exerciseinduced asthma which is characterized by attacks immediately following exertion and by the lack of any long- term sequelae or increase in airway reactivity

• Question 426:

  A 55-year-old woman presents to your office with painful hands, causing difficulty opening jars and turning the key in the ignition of her car. She is fatigued and she notices joint stiffness, but limbers up by lunch. She has trouble getting her rings off because of enlarging knuckles. About a year ago, she tried some OTC ibuprofen, which seemed to help, but led to the development of a bleeding ulcer severe enough to require transfusion and ICU care. Otherwise, her health is good, and her review of systems is negative. Your physical examination reveals tenderness and swelling at the index proximal interphalangeal and metacarpophalangeal joints bilaterally. There are small effusions on both knees. She has tenderness to lateral compression of the forefoot area bilaterally.

  The following data are obtained: normal CBC; normal basic metabolic panel; ESR 40 mm/h; ALT 90 U/L; AST 110 U/L; alkaline phosphatase 70 U/L; bilirubin 0.2 mg/dL; uric acid 5.1 mg/dL; urinalysis is normal. ACE level is normal. Rheumatoid factor is 60 and ANA is positive 1:40 speckled pattern. The next most important test would be which of the following?

  A. hepatitis C antibody
  B. anti-double-stranded DNA antibodies
  C. serum protein electrophoresis
  D. C-reactive protein
  E. RPR
  A. hepatitis C antibody

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  Explanation

  In all likelihood, this patient is presenting with a systemic inflammatory arthritis. Clearly, treatment will need to be initiated. In order to effectively and promptly treat her, you will need to understand the current state of her physiology. Therefore, basic laboratory studies including blood count, full chemistries, and urinalysis should be obtained. At this point, the most likely diagnosis is RA, and the rheumatoid factor and sedimentation rate may be helpful. Theoretically, sarcoidosis can present in this way but, epidemiologically, this is much less likely. Because of this and because the ACE level is fairly nonspecific, it should not be part of the initial workup. Neither joint fluid aspiration nor uric acid levels are likely to be diagnostic. The elevation of serum transaminase in the face of elevated sedimentation rate, moderate or low positive ANA, and rheumatoid factors raise the question about hepatitis C. About 50% of patients with active hepatitis C will have cryoglobulinemia. Cryoglobulins can produce low moderate positive rheumatoid factors. Therefore, it is extremely important in this circumstance to be certain that hepatitis C is not present. With such a low positive ANA, the likelihood that this is classical Lupus is low, and double-stranded DNA antibodies are not likely to be revealing. C-reactive protein may confirm the presence of inflammation, but it won't provide additional information over the sedimentation rate. Syphilis, "the great imitator," again may occasionally have arthritis as a manifestation--but rarely without other features. The remaining studies while they might be useful later but are unlikely to be helpful as the next most important test obtained. The probable source of the patient's symptoms is RA. Osteoarthritis can produce articular swelling, but on physical examination, there is rarely bogginess in the synovium. Anti-CCP antibody is an antibody directed against the citrullinated portion of fillagen. It has the highest specificity for RA of any antibody known. It is usually present early and may predict more severe disease.

• Question 427:

  A37-year-old White executive secretary comes to you after she found a lump in her right breast while she was showering. She describes a lesion beneath her right nipple. You question her about her personal and family history. She began menarche at age 12, and she is still having regular menstrual periods. She has had two children; the first was born when she was 25 years old. She has no family history of breast, ovarian, or colon cancer on either her maternal or paternal side. You perform a physical examination including a careful examination of her breasts. You note that her breasts contain many small cysts bilaterally. However, you also palpate a localized, firm, nontender mass below the right areola. You also describe a peau d'orange appearance of the areola. What should you advise her?

  A. She appears to have fibrocystic disease and that she should return for a repeat physical examination in 6 months.
  B. Ask her to make another appointment to see you in 2 months.
  C. Order a mammogram.
  D. Obtain serum markers CA-27/29 and CEA.
  E. Order a breast ultrasound.
  C. Order a mammogram.

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  Explanation

  Any new palpable breast lesion in females (or males) of any age necessitates a mammographic evaluation and biopsy. Delay is inadvisable. Serum tumor markers, such as CA-27/29 (or even less specifically CEA), are useful to follow tumor response to therapy; however tumor markers are not reliable as diagnostic tools in breast cancer because of a relatively low sensitivity. Lobular carcinomas are frequently not visualized on mammogram, particularly standard mammograms; ultrasound however detects these tumors and should be ordered when a palpable lesion is not detected on a mammogram.

• Question 428:

  A 64-year-old male with a history of hypertension and tobacco abuse presents for follow-up after a routine physical during which he was found to have 45 red blood cells (RBCs) per high-power field (HPF) on a screening urinalysis. The urinalysis was negative for leukocytes, nitrites, epithelial cells, and ketones. The patient denies any complaints and the review of systems is essentially negative .

  A. change of antihypertensive agent and recommendation to patient to discontinue smoking
  B. image the upper and lower urinary tracts
  C. antibiotics for 1 month
  D. expectant management with follow-up urinalysis in 6 months
  E. nephrology consultation
  B. image the upper and lower urinary tracts

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  Explanation

  Asymptomatic microscopic hematuria is defined by the American Urological Association as three or more RBCs per high power field on urinary sediment from two out of three properly collected urinalyses. A proper sample can be a midstream clean-catch specimen. The urine dipstick is roughly 91100% sensitive and 65- 99% specific for detection of RBCs, Hgb, and myoglobin. Urine dipstick is not reliable in distinguishing myoglobin from Hgb or RBCs. Therefore, urinalysis with microscopy should be ordered to assess the number of RBCs per high power field. Microscopic hematuria is usually an incidental finding but deserves a thorough workup, as 10% can be due to malignancy. The initial approach is to repeat the urinalysis to rule out infection. If the urinalysis suggests infection by the presence of WBCs or nitrites, a culture should be ordered and the patient treated appropriately. If RBCs are present without any leukocytes, nitrites, or epithelial cells on the repeated urinalysis, a proper workup should ensue.

  After history and physical are done to rule out risk factors, comorbidities, or other etiologies to account for the hematuria, one must look to diagnostic tests. A serum creatinine is useful to assess for renal insufficiency. During the course of the workup, if the urinalysis and serum creatinine suggest a glomerular etiology (casts, elevated creatinine, dysmorphic RBCs) a renal consultation and possible renal biopsy may be warranted. Evaluation of the upper tract with either an IVP or CT scan of the abdomen/ pelvis with and without contrast should be ordered to rule out renal cell carcinoma, nephrolithiasis, or aneurysms. Next, the lower tract should be visualized by cystoscopy and washings sent for cytology. If all the above workup is negative, the patient can be reassured and followed with a repeat urinalysis in 6 months.

• Question 429:

  The patient is a 52-year-old male presenting to the emergency room with complaints of severe leg pain. The patient states he has had ongoing left knee pain of 6 months' duration, unrelieved by NSAIDs but improved with vicodin. He denies any trauma but claims to have arthritis. His vital signs are stable. Physical examination of his knee demonstrates no significant findings except for decreased range of motion but with little effort. There is no swelling, erythema, or signs of trauma. An x-ray is obtained which is read as "normal," without evidence of arthritis. He asks for narcotic analgesics, but when he is offered a trial of NSAIDs and a referral to a specialty clinic, he becomes angry and walks out of the emergency room. Which of the following would be the most appropriate management should this patient return?

  A. accusation regarding drug-seeking behavior
  B. admission to a psychiatric facility
  C. confrontation and further evaluation
  D. notification of the police
  E. referral to a psychiatrist
  C. confrontation and further evaluation

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  Explanation

  Explanations:

  This case is a characteristic presentation for malingering. Consciously producing symptoms in order to assume the sick role is the motivation behind factitious disorder. There is no evidence of psychotic symptoms as would be seen in delusional disorder. Hypochondriasis involves the preoccupation with fears of having a serious illness rather than the focus on complaints of pain. The unconscious production of symptoms due to unconscious conflict is the hallmark of conversion disorder, which presents with a neurologic deficit. Malingering, which is not considered a mental illness, is defined as the intentional production of symptoms motivated by external incentives. These incentives may include such things as avoidance of work, military duty, and jail, or the acquisition of drugs (which is seen in the above case) (DSM IV-TR). In cases of suspected malingering, accusations or law enforcement involvement will likely result in further hostility and harm to any therapeutic alliance. Referral for admission to a mental health facility or to a psychiatrist may also have the same effect and is not warranted unless another mental illness or safety concerns are present. While limit setting is absolutely necessary with these individuals, a professional demeanor must be maintained. Gentle confrontation coupled\ with a focus on understanding their underlying problems (leading to their feigning illness) are the most helpful approaches. Amore complete evaluation may be necessary to determine whether or not there is an additional mental illness or substance dependence that will need to be treated.

• Question 430:

  A 42-year-old man presents to your clinic with a 1-week history of pain and inflammation involving his right first metatarsophalangeal (MTP) joint. He describes the pain as sudden in onset and worse at night. He denies experiencing any fever or traumatic injury to the joint and states that he has never had this type of pain before. He denies any chronic medical conditions, any prior surgery, and any current medication use. Besides an erythematous and exquisitely tender right first MTP joint, the remainder of his physical examination is unremarkable. Which of the following interventions is most appropriate at this time for your patient's condition?

  A. probenecid
  B. allopurinol
  C. indomethacin
  D. sulfinpyrazone
  E. aspirin
  C. indomethacin

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  Explanation

  This patient's presentation is consistent with gout. Aspiration of his first MTP joint is likely to reveal the presence of needle-shaped, negatively birefringent crystals. Rhomboid-shaped, positively birefringent crystals are characteristic of calcium pyrophosphate deposition disease, or pseudogout, with the knee being the joint most commonly affected. Nonbirefringent crystals are found in hydroxyapatite crystal deposition disease. The synovial fluid from joints affected by gout typically show evidence of inflammation in the form of leukocytosis with a predominance of polymorphonuclear neutrophils. The presence of bacteria in synovial fluid is characteristic of infection rather than gout, although gout and infectious arthritis may coexist. (Cecil Textbook of Medicine, pp. 17031708) Acute gouty arthritis usually presents in a monoarticular or oligoarticular distribution, with the first MTP joint most commonly affected. The diagnostic gold standard is detection of urate crystals within the synovial fluid of affected joints.

  It most commonly affects adult men with a peak incidence in the fifth decade of life. While patients with gout typically also have hyperuricemia, only a small fraction of the people with hyperuricemia actually have or will develop gout.

  Tophi are primarily seen in patients with long-standing hyperuricemia and is considered a finding of chronic gouty arthritis. As the disease progresses, acute attacks become more frequent and last longer if left untreated. Indomethacin inhibits the prostaglandin synthesis that facilitates the inflammation of acute gout and inhibits the phagocytosis of urate crystals by leukocytes. This inhibits the cell lysis and release of cytotoxic factors that initiate the inflammatory cascade. Allopurinol (an inhibitor of urate synthesis) and probenecid and sulfinpyrazone (promoters of urate excretion) are useful for preventing gout but are not effective during an acute gout attack. Aspirin is inappropriate in the treatment of gout since it can inhibit urate elimination and, therefore, increase hyperuricemia.