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Difficulty: EasyOrdering Laboratory Tests

A 42-year-old woman comes to the primary care clinic complaining of progressive fatigue, weakness, and dyspnea on exertion over the past 3 months. She also reports a recent, strong craving to chew ice. Her medical history is unremarkable, and she takes no medications. She reports having heavy menstrual periods that last 7 to 8 days each month. Vital signs are within normal limits. Physical examination reveals noticeable pallor of the conjunctivae. Which of the following is the most appropriate initial laboratory evaluation to order for this patient?

  1. Complete blood countAnswer
  2. B
    Serum ferritin and iron profile
  3. C
    Prothrombin time and activated partial thromboplastin time
  4. D
    Fecal immunochemical test
  5. E
    Direct antiglobulin test

Answer

Complete blood count
The correct answer is the complete blood count. In any patient presenting with signs and symptoms of anemia (fatigue, pallor, pica), the standard initial step in laboratory evaluation is to obtain a complete blood count. This test confirms the diagnosis of anemia by measuring hemoglobin and hematocrit. Furthermore, it provides the mean corpuscular volume, which categorizes the anemia into microcytic, normocytic, or macrocytic, thereby directing the subsequent sequence of targeted laboratory testing.

Step-by-Step Solution

1
Identify the patient's primary clinical syndrome.
The patient presents with fatigue, dyspnea, pica (ice chewing), and conjunctival pallor, which is the classic presentation of anemia.
Recognizing the clinical signs of anemia is required to select the appropriate diagnostic pathway.
2
Determine the most likely etiology based on the history.
The history of heavy, prolonged menstrual periods points to chronic blood loss as the primary cause.
Identifying the likely source of blood loss helps narrow down the differential diagnosis to iron deficiency anemia.
3
Select the most appropriate initial laboratory test.
A complete blood count is selected to confirm the low hemoglobin and hematocrit and assess the mean corpuscular volume.
Standard medical guidelines dictate that a complete blood count is the universally accepted initial screening test for any suspected anemia before ordering specific confirmatory panels.

Key Concept

The initial laboratory evaluation for suspected anemia, even when the etiology seems clinically obvious, is a complete blood count.
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Ordering Laboratory Tests

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