We are grateful to Drs. Alonso and Banqueri for pointing out the typographical error in our reformatted figure of the originally published algorithm for the preoperative evaluation and management of anemia1; as specified in the algorithm, for the patients with transferrin saturation less than 20% and ferritin levels 30–100 μg/dl, empiric iron therapy is appropriate to rule out the possibility of iron deficiency. On the other hand, it is noteworthy that the threshold of 20% for transferrin saturation is also empiric, so that values above this threshold do not necessarily exclude iron deficiency, particularly in patients who are unresponsive to erythropoiesis-stimulating agent therapy. For example, the recently issued Kidney Disease: Improving Global Outcomes guidelines for patients with chronic kidney disease recommend a trial of iron therapy for patients with transferrin saturation less than 30%.2Similarly, suggested ferritin levels are also empiric in the Kidney Disease: Improving Global Outcomes guidelines; the recently published National Comprehensive Cancer Network guidelines recommend a trial of iron therapy for patients with cancer for whom anemia has been unresponsive to erythropoiesis-stimulating agent therapy with ferritin levels less than or equal to 800 ng/ml and transferrin saturation less than 20%.3
The authors also advocate the use of reticulocyte values and red cell size to entertain the possibility of undiagnosed hemolytic anemias such as in patients with thalassemia. Our cited algorithm was designed to be initially focused on iron-restricted erythropoiesis because of its high prevalence in both normal populations and in a variety of important patient settings, including a significant percentage of the elderly.4Because preadmission testing and evaluation of anemia in patients scheduled for elective surgery has been shown to identify unexpected anemia in up to 30% of patients scheduled for elective orthopedic surgery,5the conclusion is that traditional anemia workups based on red cell size (mean corpuscular volume)6(as traditionally taught to undergraduate physicians and in textbook chapters) are not recalled, too complex, or not used effectively by primary physicians (family practitioners, internists, and gynecologists) who need to be able to evaluate these anemias. In addition, microcytosis is nonspecific because the anemia of inflammation, as an iron sequestration syndrome, can also manifest microcytosis. Furthermore, the mean corpuscular volume has only a 70% sensitivity for identifying iron deficiency.7Finally, a hematology consult is always appropriate if and when the algorithm fails to diagnose the cause of the patient’s anemia.
*Stanford University, Stanford, California. email@example.com