Iron Deficiency Anemia

Although the gold standard for diagnosing iron deficiency anemia is a bone marrow biopsy (which is understandably unpopular), serum ferritin has largely replaced this in day-to-day practice. In fact, a serum

Ferritin < 40

is about 98% specific and 95% sensitive in diagnosing iron deficiency anemia. The problem, however, is that ferritin acts as an acute phase reactant (like the sedimentation rate). So any inflammatory process can falsely elevate the ferritin and fool you into believing that your patient does not have iron deficiency anemia (when she really does).