USMLE-STEP-3 Online Practice Questions and Answers

Correct Answer: E Section: (none)

Explanation:

The patient's history and examination are worrisome for pancreatic disease, and he has strong signs of pancreatic insufficiency. His long history of alcohol use suggests the possibility of chronic pancreatitis or pancreatic cancer. Fecal fat studies would only confirm or quantify his steatorrhea. ACT scan would image the pancreas for changes consistent with chronic pancreatitis (duct dilation, calcifications, pseudocysts) and could look for a neoplasm of the pancreas as well. ERCP is not indicated as a first-line test in patients with abdominal pain given its risk of causing acute pancreatitis. Upper endoscopy would be helpful to rule out peptic ulcer disease and other gastric complaints, but would not provide more global information about the abdomen. The patient has greasy stools and weight loss, findings seen in patients with steatorrhea due to chronic pancreatitis. Patients with steatorrhea malabsorb fat-soluble vitamins (vitamins A, D, E, and K). "Night blindness" (poor night vision) due to vitamin Adeficiency is common among patients with advanced chronic pancreatitis and likely led to this patient's motor vehicle accident. The patient has DM as a consequence of pancreatic endocrine insufficiency, another feature of chronic pancreatitis. Diabetes develops when greater than 8090% of the gland has been destroyed. Patients with chronic pancreatitis have a coexisting loss of glucagon from islet cells and, thus, often become brittle diabetics, with hypoglycemia seen after insulin administration. Vitamin K and B12 deficiency, which the patient may have, do not cause hypoglycemia. The patient was previously noted to eat well, so inadequate oral intake is unlikely. Diabetic education should decrease the rate of chronic insulin overdosage.

The patient has pancreatic exocrine insufficiency and thus cannot produce enough pancreatic enzymes to digest his food. Pancreatic enzyme replacement therapy in tablet form is a mainstay of therapy for chronic pancreatitis. It can rapidly reverse this problem by providing exogenously produced pancreatic enzymes to break down fats, carbohydrates, and proteins for absorption in the small bowel. The patient would not benefit from additional oral feedings without enzyme supplementation and would only worsen his steatorrhea by doing so. He can take food orally, so feeding via gastrostomy, TPN, or PPN are not indicated. The patient's worsening pain and weight loss despite therapy is worrisome for the development of pancreatic cancer. CA-19-9 is frequently (but not universally) elevated in pancreatic cancers, although it can be elevated in cholangiocarcinoma as well. PSA is associated with prostate cancer. CEA is associated with colon cancer. CA-125 is associated with ovarian cancer. AFP is associated with hepatocellular carcinoma.

Correct Answer: C Section: (none)

Explanation: The patient has the typical features of PCOS associated with insulin resistance and the metabolic syndrome. The presence of hyperandrogenism and oligomenorrhea, without other known causes (such as congenital adrenal hyperplasia), makes the diagnosis of PCOS. The hirsutism and acne are the result of the hyperandrogenism associated with PCOS. Thyroid disorders and hyperprolactinemia can contribute to menstrual disturbances but would not be expected to cause the signs of androgen excess or A. nigricans. A cosyntropin stimulation test would be used for the diagnosis of adrenal insufficiency. Growth hormone levels may be elevated in acromegaly or in some pituitary tumors. Women with PCOS have a high risk of glucose intolerance, diabetes, dyslipidemia, and hypertension. Individuals with insulin resistance syndromes typically exhibit hypertriglyceridemia with low HDLlevels. The key to management of PCOS is weight loss. Even modest weight loss (1020 lbs) can result in significant improvement in metabolic and physiologic parameters, such as blood pressure and insulin resistance, and improved fertility.

Correct Answer: B Section: (none)

Explanation:

A questionable history of penicillin allergy by a patient often incorrectly labels patients as penicillin allergic. Physicians are often afraid of a true anaphylactic reaction and turn to a second-line medication. Most patients who state they were penicillin allergic or were told by a parent they were allergic were confusing a complication of the illness, such as a rash from viral prodrome. In fact, 80 90% of patients who self-report a nonanaphylactic reaction or were informed by a parent of a penicillin allergy are not penicillin allergic when assessed with skin allergy testing. The frequency of all adverse reactions to penicillin in the general population ranges from 0.7 to 10%. Approximately 98% of patients with a reported history of penicillin allergy (except anaphylaxis) and a negative skin test can safely receive penicillin. In patients who have an unclear history of penicillin allergy (pretest likelihood greater than that of general population) and who would benefit from penicillin, skin testing should be performed and penicillin used for patients with negative results. If however, the pretest likelihood of allergy is similar to the prevalence in the general population, skin testing can be foregone, and treatment with penicillin offered. In patients with definite penicillin allergy or anaphylaxis in whom penicillin therapy is the only option, inpatient admission for penicillin desensitization is warranted.

Correct Answer: A Section: (none)

Explanation:

Pubarche in females is usually earlier than in males. Delayed puberty alone may be a pathologic condition; its presence in conjunction with short stature makes a pathologic state more likely. Males do, indeed, have adrenarche. Panhypopituitarism is a cause of puberty delay, but not a common one. Undiagnosed hypothyroidism can be a cause of pubertal delay, and thyroid function testing should be a part of the routine evaluation of this problem. The onset of puberty in males is usually signaled by an increase in testicular volume. This is commonly seen in conjunction with lengthening of the phallus and thinning of the scrotal skin. As a result of puberty, the other findings (deepening of the voice, increased muscle mass, and increased facial hair) may be seen, but the first of the listed findings to appear is increased testicular volume. In females, puberty is usually signaled by the enlargement of breast buds.

Correct Answer: B Section: (none)

Explanation:

While patients with bipolar depression do present with psychotic features, this individual does not give any history of manic episodes, making the diagnosis difficult at this time. The bizarre delusions (those that cannot possibly exist in life) and auditory hallucinations that this patient has are not consistent with delusional disorder. Schizoaffective disorder, depressed type, includes both psychotic as well as depressive symptoms. However, the psychotic symptoms must last at least 1 month and occur in the absence of a depressed mood. The diagnosis of schizophrenia also requires at least 1 month of active psychosis but a total of 6 months of attenuated or residual symptoms. Although a depressed mood is very commonly seen in schizophrenia, the total duration of depression is brief overall compared to the psychotic symptoms. This patient presents with major depression with psychotic features, consisting of a depressed mood with neurovegetative symptoms for at least 2 weeks, as well as psychotic symptoms, which are only present along with the mood symptoms (DSM IV-TR).

Mood stabilizers alone or with antipsychotic medications are not the first-line treatments for major depression with psychotic features, but rather for mania with or without psychotic features. Studies have demonstrated that the combination of antidepressants and antipsychotics is more effective in treating major depression with psychotic features than either pharmacotherapy alone.

Correct Answer: E Section: (none)

Explanation: Explanations: The Third Report of the National Cholesterol Education Program Expert Panel on the Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (ATP III) was published in May 2001 by the National Heart, Lung, and Blood Institute of the National Institutes of Health. This evidence-based report provides guidelines for the evaluation and management of blood lipid levels for the primary and secondary prevention of heart disease. The basis of the recommendations for management is an overall evaluation of an individual's risk factors for developing cardiovascular disease. Persons at the highest risk for future cardiac events are those with already established coronary artery disease or "coronary artery disease equivalents," which include diabetes mellitus, other forms of atherosclerotic disease, or multiple risk factors that confer a 10-year CHD risk of greater than 20%. Multiple studies have shown that elevated LDL cholesterol levels are a risk for coronary artery disease and that lowering LDL levels can reduce the risk of events.

ATP III goals are targeted at LDL levels. For persons with LDL levels above this goal, the options for lowering LDL can include therapeutic lifestyle changes, lipid-lowering medications, or a combination of both. In a patient with coronary artery disease, diabetes mellitus, or other CHD equivalents, the LDL goal level is 100 mg/dL. In this population, therapeutic lifestyle changes alone would be recommended for those with LDL levels of 100130 and medication could be started concomitantly with lifestyle changes for those with LDL above 130, as most persons would require medication to achieve the recommended goal. For the patient in this question with an LDL of 160 mg/dL, therapy with an HMG-CoA reductase inhibitor would be recommended first-line therapy to try to get his LDLto goal. Therapeutic lifestyle changes alone would be very unlikely to reduce his LDL to less than 100 mg/dL, but are still an important part of his overall lipid management program and should be recommended along with medication therapy. Neither increasing his dosage of metformin nor adding insulin would be recommended as they would not be expected to improve his dyslipidemia significantly and because his diabetic control is appropriate. At his follow-up visit, the patient's lipid levels have met the recommended guidelines; therefore, the recommendation would be to continue with his current therapy. Increasing the dosage of his statin, adding a fibric acid, nicotinic acid, or referring the patient to a dietician would all be appropriate considerations in someone who had not successfully reached his goal lipid levels.

A recent addition to the ATP III provides an option for changing the target LDL goal for those at the highest of risk for coronary events. For persons with known coronary artery disease, or CAD equivalent, and multiple risk factors, such as diabetes or continued smoking, one could consider using an LDL of 70 as a goal. For this patient, with diabetes but no history of CAD or equivalent, the recommended goal would remain an LDL of 100 or less. Immunizations should be a routine part of the adult health maintenance evaluation. All patients with diabetes are recommended to be vaccinated with the pneumococcal vaccine (PPV-23) both because of the incidence of pneumonia in diabetics and the increased risk of complications should infection occur. A recent recommendation for all adults is to provide a single dose of Tdap vaccine in place of one booster dose of Td. The rationale for this is to attempt to reduce the incidence of pertussis in the population, as pertussis has been recurring in the United States in spite of routine childhood vaccination. Hepatitis A and B are routine vaccinations for children. The current recommendation for adult immunizations against these diseases is to target high-risk adults. Diabetes is not considered a high risk for these infections. Herpes zoster vaccine is recommended for adults over the age of 60

Correct Answer: A Section: (none)

Explanation:

Explanations:

Understanding the concepts of sensitivity, specificity, PPV, and NPV is crucial to interpreting diagnostic test

results. Sensitivity is defined as the percentage of people who have a disease who test positive for that

disease. Specificity is defined as the percentage of people who are free of a disease who test negative.

These two concepts are considered characteristics of the specific test in question and are independent of

the prevalence of the disease in the population. The PPVs and NPVs of a test are the test's clinical

characteristics and these concepts are directly related to the prevalence of the disease in the population.

The PPV is the percentage of people who have a positive test result who actually have the disease.

Similarly, the NPV is the percentage of people who have a negative test result who don't have the disease.

While the definitions may seem subtly different, the implications are significant. The usual way to calculate sensitivity, specificity, PPV, and NPV is with the table, using the following definitions

The definitions of sensitivity, specificity, PPV, and NPV would then be:

Sensitivity = a/(a + c)

Specificity = d/(d + b)

PPV = a/(a + b)

NPV = d/(d + c)

The specific information in this question comes from an article describing a study of B-type natriuretic

peptide (BNP) for the diagnosis of CHF. The data presented show that 106 persons tested positive using

the BNP test. After comparison with the "gold standard," in this case, a review by expert cardiologists, 95 of

these 106 were determined to truly have CHF. Therefore, 11 of the 106 were false positives and 95 were

true positives. Similarly, 144 persons tested negative using the BNP test. Of these, 142 were confirmed as

true negatives and 2 were determined to be false negatives.

Putting these numbers into a table reveals:

The calculations then become:

Sensitivity = a/(a + c) = 95/(95 + 2) = 98%

Specificity = d/(d + b) = 142/(142 + 11) = 93%

PPV = a/(a + b) = 95/(95 + 11) = 90%

NPV = d/(d + c) = 142/(142 + 2) = 99%

Correct Answer: D Section: (none)

Explanation:

Organ donation can often be a very sensitive topic. As the transplant waiting lists continue to grow, the process of approaching the family of potential organ donors has been of great interest. In this setting, it is important to provide adequate information in a nonthreatening manner. Even today with donor cards, living wills, and so on, there can still be conflict between the patient and family, or even amongst family members, with regard organ transplantation. An individual who has been trained to discuss organ transplantation with grieving families best addresses this sensitive topic. Furthermore, regardless of the decision after appropriate discussions are held, it is vital to respect the family's choice.

Correct Answer: B Section: (none)

Explanation:

When acetaminophen is taken in normal doses, it is conjugated in the liver to harmless glucuronide and

sulfate metabolites. These metabolic pathways become easily overwhelmed in the setting of a large

overdose, however. If this occurs, the cytochrome P450 system directs conversion of the excess

acetaminophen to a compound called NAPQI, which is conjugated with glutathione to form a nontoxic

mercapturate metabolite. Once glutathione stores are exhausted in the liver, however, the excess NAPQI

combines with proteins within hepatic cells causing hepatic cell death. Taurine is a mercaptan-containing

amino acid involved in bile acid biochemistry. Citrulline aids in the detoxification and elimination of

ammonia. Ornithine plays an important role in the urea cycle.

N-acetylcysteine should be administered as promptly as possible for treatment of acetaminophen

overdose. It works by helping restore hepatic glutathione stores and by providing sulfhydryl groups that bind

toxic metabolites. N-acetylcysteine is administered orally in the form of an initial loading dose (140 mg/kg)

followed by 17 doses (70 mg/kg each) given every 4 hours. In addition to this oral therapy, the Food and

Drug Administration (FDA) approved 21-hour and 48-hour long intravenous treatment regimens in 2004.

Left untreated, acetaminophen overdose carries a significant risk for hepatic failure and subsequent death

depending on the amount of acetaminophen ingested, the presence of any preexisting liver disease, and

interactions with any other medications that induce cytochrome P450 enzyme activity. Naloxone,

flumazenil, and physostigmine are given as antidotes for toxicity related to opioid analgesics,

benzodiazepines, and muscarinic receptor blockers, respectively.

Poor prognosis is associated with elevated serum lactate levels (above 3.5 mmol/L), acidemia (arterial pH

less than 7.3), renal failure, and coagulopathy. The Rumack-Matthew nomogram provides a means of

determining whether an individual falls into the possible-, probable-, or high-risk categories for developing

hepatotoxicity based on serum acetaminophen levels and the number of hours since ingestion. Therapy

with N-acetylcysteine is most effective if begun within 8 hours of the toxic ingestion but still has proven

benefit if started within 24 hours

Correct Answer: C Section: (none)

Explanation: Multiple myeloma is a plasma cell dyscrasia that is characterized by involvement of the skeleton in multiple sites. The characteristic x-ray shows punched-out bone lesions that are very easily seen in the calvarium. Extension of the disease to lymph nodes and extranodal sites, such as skin, can be seen. The bone marrow biopsy and smears reveal an increased number of plasma cells, which usually constitute greater than 20% of all of the cells. The cells either diffusely infiltrate and replace the marrow elements or can be seen scattered throughout the hematopoietic elements. The neoplastic plasma cells have a perinuclear hof and an eccentrically placed nucleus which allows the recognition. In 99% of patients with multiple myeloma, electrophoretic analysis reveals increased levels of IgG in the blood, light chains (Bence-Jones proteins) in the urine, or both. The monoclonal IgG produces a high spike when seen in the serum or in the urine, subject to electrophoresis. In general, the quantitative analysis of the monoclonal IgG is more than 3 g. The clinicopathologic diagnosis of multiple myeloma rests on radiographic and laboratory findings. Marrow examination may reveal increased plasma cells or sheet-like aggregates that may completely replace the normal elements. The prognosis for this condition is variable, but generally poor.