The nurse practitioner is reviewing the chart of an 18-year-old female patient with a BMI of 18 who presented with fatigue and pale skin. Of the following lab values, which would be true in a case of iron deficiency anemia?

Choice A reason: Iron deficiency anemia is classically microcytic and hypochromic, meaning the red blood cells are smaller than normal (decreased MCV) and have reduced hemoglobin content. Additionally, RDW is increased due to anisocytosis, which reflects a wide variation in red blood cell sizes as the bone marrow releases immature cells in response to iron deficiency. This pattern is one of the earliest and most consistent hematologic findings in iron deficiency anemia. Choice B reason: A decreased RDW is not typical in iron deficiency anemia. RDW tends to rise as the body attempts to compensate for anemia by producing red blood cells of varying sizes. A low RDW would suggest a more uniform population of red cells, which is not characteristic of iron deficiency. Choice C reason: Increased MCV is seen in macrocytic anemias such as those caused by vitamin B12 or folate deficiency. Iron deficiency anemia is microcytic, not macrocytic, and therefore MCV would be decreased, not increased. Choice D reason: MCHC is typically decreased in iron deficiency anemia due to the reduced hemoglobin concentration in red blood cells. An increased MCHC would suggest hyperchromic anemia, which is not consistent with iron deficiency.