Using Reticulocyte Hemoglobin Equivalent to Screen for Iron Deficiency May Be Problematic.

Abstract

Iron deficiency (ID) is the most common nutritional deficiency globally, with a prevalence of 9.2% among children age 12 to 35 months in the United States. Iron deficiency anemia (IDA) is found in 2.1% of children in this age group.1 The developmental delays associated with ID motivate pediatricians to diagnose the iron deficient child as early and accurately as possible,2 ideally before the development of IDA. Unfortunately, traditional markers of iron stores, such as transferrin saturation or serum ferritin, are not sensitive in this age group, and both can be affected by systemic inflammation.3,4 In 2010, the American Academy of Pediatrics (AAP) published a clinical report recommending that children be screened for ID with either ferritin and C-reactive protein (CRP) or reticulocyte hemoglobin content (CHr).1 The report did not favor one testing strategy over another. Prior work has shown that CHr is an early and sensitive marker of ID,5,6 and as a result, our clinic transitioned to testing for ID exclusively with this test. Without refuting the potential utility of the test, this report aims to highlight some of the important challenges our clinic experienced while using a test of the hemoglobin in reticulocytes, as well as another important limitation of the test not discussed in the 2010 clinical report. Currently, 2 tests exist for assessing the amount of hemoglobin in reticulocytes. CHr is an older, more studied value resulted by Advia machines; reticulocyte hemoglobin equivalent (Ret-He) is a newer, less-documented value resulted by Sysmex machines. Several cutoff levels for the CHr test have been proposed,5,7 but pediatric data are lacking for the Ret-He test, and the manufacturer recommends normative testing for each machine and population (personal communication, Dr Meyers). Pediatric primary care clinicians at our urban safety-net hospital began using Ret-He to screen for ID in early 2013 when the test first became available at our institution. Subsequently, several clinicians noticed a high number of positive screens compared with their prior experience and given the estimated disease prevalence.1 The authors began a quality improvement initiative to standardize our clinic’s screening practice. A literature review established that normal values reported with the Ret-He test had been established for adults only, leading to concerns about the appropriateness of this test in our patients.