Original articleIdentifying factors predicting iron deficiency in United States adolescent females using the ferritin and the body iron models
Introduction
Iron deficiency (ID)1 is the most common form of nutritional deficiency in the United States [US; [1], [2]]. It is estimated that 9–16% of US female adolescents are iron deficient while 2–5% are anemic [1], [3], [4]. Due to lack of a simple, inexpensive test for ID, primary care screening is based on testing for anemia, which has low sensitivity and specificity for detection of ID [2], [5], [6]. This is unfortunate, as even non-anemic iron deficient adolescents experience significant morbidity, which is easily corrected with iron supplementation [7], [8], [9].
Risk assessment tools can select individuals requiring more extensive laboratory evaluation. To develop such a tool for adolescent ID screening, risk factors must be identified with data from that population. Most studies of risk factors for ID and anemia group adolescents with older reproductive age women, typically defined between 12 and 49 years of age [1], [10], [11], [12]. However, the care of adolescent females cannot be approached similarly to older women.
A challenge in developing an ID risk assessment tool is that current ID laboratory testing relies on multiple markers that, combined, determine iron status [6]. The ferritin model, which uses serum ferritin, erythrocyte protoporphyrin, and transferrin saturation to define ID, was used from the mid-1980's to 2006 to determine ID among the US population [4], [6], [13], [14]. In 2003 Cook et al. presented the body iron model in response to the need for a reliable method to both assess and quantify iron status [6], [15]. Similar to the ferritin model, the body iron model does not provide a single, simple test for ID for use in the office setting, but uses a formula with ferritin and soluble transferrin receptor. Though comparison of the prevalence of ID defined by the 2 models found fair to good agreement, the body iron model produces lower estimates of ID prevalence with better prediction of anemia and less inaccuracy from inflammation [4].
Evaluation of both ID models and associated risk factors through the lens of their utility for the development of a pediatric screening tool would fill a gap in current ID screening. Therefore, the objective of this study was to compare ID risk factors among adolescent females as defined by the ferritin and body iron models with the National Health and Nutrition Examination Survey (NHANES)2 dataset. Our hypothesis was that the two models would share enough overlapping risk factors to create a clinical prediction tool to select adolescents at high risk of ID for more costly laboratory tests or even empiric iron therapy. This implementation science-based study has the potential to replace the current low-sensitivity anemia-based screen (hemoglobin) used daily in US pediatric primary care to test adolescents for ID.
Section snippets
Data source
NHANES is a program of studies to assess the health and nutritional status of the US population [16]. The survey combines household interviews and physical examinations conducted in mobile examination centers by the National Center for Health Statistics, Centers for Disease Control and Prevention (CDC).3 NHANES includes demographic, socioeconomic, dietary, and health-related questions. Participants are selected via a stratified multistage
Demographics
A sample of 1765 adolescent females aged 12–21 years participating in NHANES 2003–2006 with the necessary laboratory data to define ID using both the ferritin model and the body iron model were included in this analysis. This sample represents 6.3% of all NHANES study participants (unweighted N = 28,127) and 65.4% of all adolescent women (unweighted N = 2700) in the selected years. Among the sample, 65.8% were self-described white, 14.6% black, 9.7% Mexican, 4.2% Hispanic and 5.7% other. Almost
Discussion
This analysis of a nationally representative cohort of female adolescents aged 12–21 years confirms that current anemia-based screening, with a sensitivity of only 15.6–18.8%, greatly underestimates ID and is inadequate as a widely used screening tool. Survey-based risk factors for adolescent ID showed some variability by the model used to define its presence and the prevalence of ID. However, adolescent age was a significant predictor of ID in both the ferritin model and the body iron model,
Conclusions
Anemia-based screening is widely utilized in primary care, but fails to detect the majority of iron deficient adolescent females. Currently, universal laboratory testing for adolescent ID is impractical in the clinical setting. Identification of adolescent age as a common risk factor between the ferritin and body iron models may inform age-based recommendations on ID screening as well as prospective studies on optimizing adolescent ID screening.
Conflict of interest
None declared.
Acknowledgments
Dr. Sekhar's research is supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health under BIRCWH award number K12HD055882, “Career Development Program in Women's Health Research at Penn State.” The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.
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