A 16-year-old girl comes to the office due to fatigue for the past few months. She attends high school and plays on the school soccer team but says that her endurance has decreased. The patient sleeps 9 hours a night and has been a vegetarian for the past year. She reached menarche at age 13 and has had regular menses for the past 6 months. The patient is not sexually active and does not smoke cigarettes but does report drinking 1 or 2 cans of beer a month. Her blood pressure is 110/60 mm Hg, pulse is 70/min, and BMI is 21 kg/m². Physical examination shows a well-nourished teenage girl with pale conjunctivae. Her hemoglobin is 9.2 g/dL. Which of the following sets of additional laboratory findings are most likely to be seen in this patient?

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11ec160b_3984_d2df_9249_8bce52b473bd_MD0001_00 This girl has fatigue and conjunctival pallor, which are suggestive of anemia. The diagnosis is confirmed by her low hemoglobin. Women of childbearing age are at risk for iron-deficiency anemia due to menstrual cycle blood loss, especially teenage girls who have higher iron requirements due to growth. In this patient, decreased consumption of dietary iron (eg, vegetarianism) is an additional risk factor. As iron deficiency develops, the following sequence can be seen with laboratory testing: Ferritin is an intracellular iron-storage protein that is used as a serum marker of total body iron stores. It is decreased in iron deficiency and elevated in iron overload or during infection/inflammation (acute phase reaction). Transferrin transports iron through the plasma. When iron levels are normal, approximately one third of circulating transferrin is bound to iron. In iron deficiency, hepatic synthesis of transferrin increases but transferrin saturation drops due to decreased release of iron into the plasma from intracellular stores. (Choice A) The earliest signs of iron deficiency are low serum ferritin and high serum transferrin, which manifest before overt anemia develops. This pattern of findings is more consistent with α- or β-thalassemia, which usually cause microcytic anemia with normal ferritin and transferrin levels. (Choice C) Circulating transferrin levels would increase and MCV would decrease in a patient with iron-deficiency anemia. (Choice D) Low hemoglobin in the setting of a normal MCV, low circulating transferrin, and high serum ferritin is suggestive of anemia of chronic disease, which is often associated with infections and inflammatory conditions. Other acute phase reactants (eg, C-reactive protein, sedimentation rate) are usually elevated in these patients. (Choices E and F) Hypersegmented neutrophils are characteristic of megaloblastic anemias, which can be caused by folate and vitamin B₁₂ deficiency. Folate deficiency is unlikely in this patient, as folate is found in many vegetable products. Although vegetarians are at risk for vitamin B₁₂ deficiency, depletion of hepatic B₁₂ stores takes several years, and this patient has been a vegetarian only for the past year. Educational objective: Anemia in a woman of childbearing age is most commonly caused by iron deficiency secondary to menstrual blood loss. Iron deficiency is associated with decreased serum ferritin, increased total iron-binding capacity (transferrin), and microcytic, hypochromic red blood cells. __________ References: Guideline for the laboratory diagnosis of functional iron deficiency. (http://www.ncbi.nlm.nih.gov/pubmed/23573815)

A 16-Year-Old Girl Comes to the Office Due to Fatigue