If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 2 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.
This month’s stumper
A 14-year-old girl comes to the physician because of heavy menstrual bleeding that began with menarche two years ago. Her menstrual periods last eight to 10 days and occur approximately every 28 days. Her last menstrual period ended three days ago. Vital signs are temperature 37.0ºC (98.6ºF), blood pressure 110/70 mm Hg, pulse 90/min and respirations 18/min. Physical examination shows a slender, calm girl who is in no distress but appears pale. The remainder of the examination is unremarkable. Laboratory studies show:
- WBC: 7,000/mm3
- Hb: 9 g/dL
- Hct: 27%
- Plt: 250,000/mm3
Which of the following is the most appropriate next step in management?
A. Begin a transfusion of packed red blood cells
B. Order a pelvic ultrasound to rule out polycystic ovaries
C. Order coagulation profile
D. Reassure that heavy bleeding is caused by anovulatory cycles
E. Start oral contraceptive therapy
The correct answer is C.
Kaplan Medical explains why
Dysfunctional uterine bleeding (in this case, menorrhagia, or prolonged menstrual bleeding that occurs at regular intervals and lasts more than seven days) is often the presenting symptom of a blood dyscrasia. The most common inherited disorder of bleeding, von Willebrand disease, is generally transmitted as an autosomal-dominant trait and is more commonly diagnosed in women, because it might present with heavy bleeding at menarche as in the vignette.
Lab findings associated with von Willebrand disease are normal PT and either normal or slightly prolonged aPTT. Platelet count is normal. Bleeding time is increased, however, because vWF is required for normal binding of platelets to blood vessels. Factor VIII and vWF are usually decreased. Ristocetin activity (vWF activity) is always abnormal. von Willebrand disease is often not diagnosed until severe bleeding after surgery or when noted on menarche. Patients who have von Willebrand disease often have family histories of abnormal bleeding.
Why you shouldn’t choose the other answers
Read these explanations to understand the important rationale for each answer.
Choice A: Transfusion of packed red blood cells is incorrect. The patient in the question is not unstable (mild tachycardia, stable blood pressure), and because she is not currently bleeding, she can be managed as an outpatient without the need of a transfusion.
Choice B: Pelvic ultrasound to rule out polycystic ovaries is incorrect. Although polycystic ovary syndrome is a common cause of dysfunctional uterine bleeding, it is marked by irregular cycles and heavy bleeding (menometrorrhagia). The patient here is not typical of polycystic ovary syndrome in that she is not overweight.
Choice D: Reassurance that heavy menstrual bleeding is likely secondary to anovulatory cycles is incorrect. Although dysfunctional uterine bleeding is often secondary to anovulatory cycles in the first few years after menarche, what distinguishes this patient’s bleeding is that she began with heavy, prolonged periods at menarche. The patient’s anemia also demands that further diagnostic studies be done.
Choice E: Oral contraceptive therapy is incorrect. Once von Willebrand disease is diagnosed, the treatment of oral combined contraceptives and oral iron therapy can be started, but it would be incorrect to begin treatment without performing further diagnostic studies first.
One tip to remember
Von Willebrand disease is the most common inherited bleeding disorder and should be thought of when a young girl presents with heavy bleeding since the onset of menses. von Willebrand factor (vWF) is instrumental in linking platelets to endothelial cells and acts as a carrier for clotting factor VIII, which is found at low levels and has a short half-life if vWF is absent. Laboratory testing for vWF antigen, vWF activity and factor VIII activity is usually enough to make the diagnosis.
For more prep questions on USMLE Steps 1, 2 and 3, view other posts in this series.
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