A 28-year-old woman presents to the clinic for evaluation of fatigue and decreased exercise tolerance over the past 3 months. She reports heavy menstrual periods lasting 7 to 8 days each month. She has no other medical conditions and takes no medications. Vital signs are within normal limits. Physical examination reveals pale conjunctivae.
Laboratory studies show:
| Test | Result |
|---|---|
| Hemoglobin | 9.2 g/dL |
| Mean corpuscular volume (MCV) | 72 fL |
| White blood cell count | 6,500/mm³ |
| Platelet count | 410,000/mm³ |
Which of the following laboratory findings is most likely to be present in this patient?
- Decreased serum ferritinAnswer
- BDecreased total iron-binding capacity (TIBC)
- CElevated hemoglobin A2 level
- DNormal red cell distribution width (RDW)
- EPositive direct antiglobulin test
Answer
Decreased serum ferritin
The correct answer is decreased serum ferritin. This patient's history of heavy menses, combined with a microcytic anemia (low MCV) and a reactive thrombocytosis, strongly points to iron deficiency anemia (IDA). Ferritin is the primary intracellular iron-storage protein, and a decreased serum ferritin level is the most specific laboratory finding for confirming IDA. As iron stores are depleted from chronic blood loss, ferritin levels drop.
Step-by-Step Solution
Key Concept
Iron deficiency anemia is the most common cause of microcytic anemia in premenopausal women with heavy menses and is characteristically confirmed by a decreased serum ferritin level.