Changing the Serum Ferritin Lower Limit of Normal to a Clinical Decision Limit: An Acceptability Survey
Authors: Phillips Zoe , Tang Grace , Thillaye-Kerr Rowan , Fralick Michael , Weyand Angela C , Crowther Mark A. , Selby Rita , Sholzberg Michelle 
Published: December 2024

Background
Iron deficiency is the most common cause of anemia globally and disproportionately impacts children and women. The symptoms of iron deficiency with or without anemia negatively impact health-related quality of life and are reversible with treatment. The most reliable diagnostic test for iron deficiency, in the absence of concomitant inflammation, is serum ferritin. Multiple recent studies demonstrated that the current ferritin thresholds are inappropriately low (particularly for females), leading to widespread underdiagnosis of iron deficiency.
Lack of clear, consistent clinical decision limits for serum ferritin is a barrier to diagnosing and managing patients with iron deficiency. Changing the ferritin lower limit of normal to a clinical decision limit of &lt;30 µg/L for adult patients and &lt;20 µg/L for pediatric patients may prompt healthcare providers to recognize and appropriately manage iron deficiency. The acceptability of such a change amongst health care providers who order serum ferritin is not known, but is important to assess in order to understand provider uptake and develop effective knowledge translation interventions.
Methods
An electronic survey was disseminated amongst healthcare providers internationally to assess the acceptability of changing serum ferritin lower limit of normal to a clinical decision limit. Participants were identified via snowball sampling using professional connections and/or social media. Descriptive statistics were used to summarize the survey responses and the study was approved by the institutional research ethics board.
Results
A total of 165 healthcare providers participated in the survey, 93% (153/165) of whom were physicians. Approximately half (54%, 83/153) of physicians were hematologists. Other physician specialties included internal medicine (17%, 26/153), family medicine (6%, 9/153), pediatric specialties (7%, 11/153), obstetrics and gynecology (4%, 6/153), and other (12%, 18/153). Non-physician providers included nurse practitioners (7), registered nurses with expanded scope (1), nurse midwife (1), pharmacist (1), and clinical scientist (1). Respondents were from 23 countries, 38% (63/165) from Canada, 25% (42/165) from the US, and 16% (26/165) from the UK. 68% (113/165) of respondents practiced predominantly in an academic setting. 54% (90/165) worked primarily in the outpatient setting, 27% (44/165) in both inpatient and outpatient settings, and 18% (29/165) practiced in a majority inpatient setting.
All respondents indicated that they order serum ferritin on their patients. Most respondents did not have concerns about changing the ferritin lower limit of normal for adults (80%, 123/155) or children (81%, 112/138). When asked to provide reasons for concern, 32% (12/37) indicated that the proposed cut-off of &lt;30 µg/L in adults was too low and would lead to underdiagnosis, and 57% (13/23) responded in kind regarding the proposed cut-off of &lt;20 µg/L in pediatric patients. Five respondents indicated a need for further education. There were no responses indicating concern about incorrect or over-diagnosis of iron deficiency.
Conclusions
Findings from this international electronic survey demonstrated that health care provider respondents generally do not have concerns regarding implementing a clinical decision limit for ferritin of &lt;30 µg/L for adult patients and &lt;20 µg/L for pediatric patients. Among those who expressed concern, the most common concern was that the proposed clinical decision limit is still too low.