Is "30" the magic number for ferritin? (and what does that even mean on your analyzer?)

Clinical Significance

Ferritin is the primary iron storage protein and an early marker of iron deficiency, dropping before hemoglobin declines. Clinically, it plays a central role in diagnosis where underdiagnosis misses iron deficiency in vulnerable populations (pregnant patients, menstruating individuals, those with chronic blood loss), while overdiagnosis can trigger unnecessary workups, IV iron infusions, and patient anxiety. Current guidelines disagree on the optimal lower ferritin threshold for detecting iron deficiency anemia. The ASH draft guidelines recommend ≤30 µg/L for adults, though the strength of this evidence is still under review; whereas the WHO's classic <15 µg/L cutoff, may miss up to half of true deficiency.² 

Threshold Derivations

Much of the evidence driving the ASH's higher thresholds originates from the NHANES dataset, which primarily uses the Roche platform. Yale recently published a study using Roche and cited several NHANES papers, and moved their cutoff to 25 µg/L.³ However, many ASH draft guideline citations do not consistently specify the analytical platforms used in the primary studies, raising questions about how the ≤30 µg/L recommendation was derived and whether it accounts for inter-assay variability.

The Standardization Problem: Ferritin Assays Are Not Commutable

The WHO introduced three International Standards. IS1 (80/602) was derived from human liver and used in original RIA studies.⁴,⁵ IS2 (80/578) was derived from human spleen. IS3 (94/572) is recombinant L-ferritin. Beckman uses IS3; Roche uses IS1. Because original RIA assays cannot be cleanly traced to current standards, commutability remains problematic.⁶ Publications further demonstrate that ferritin reference intervals vary widely by platform.⁷,⁸ 

Platform Bias

Compared to Beckman, the Roche assay shows results ranging from 31% to 57% higher at clinically relevant decision points.⁶ In our in-house comparison, we successfully replicated the difference between Roche (CHOP) and Beckman (HUP). The Roche platform yielded values approximately 50% to 60% higher than Beckman. Furthermore, studies also show that despite labs being certified, the percentage of premenopausal women flagged as having low ferritin ranged from 11% to 53% depending entirely on which analyzer was used.⁹ This fivefold difference reflects analytical variability, not biology.

Sex-Specific Reference Intervals

Studies also note that sex-specific ferritin ranges mostly exist because women have historically been reported to have lower ferritin, which may represent underdiagnosis rather than true physiological difference.¹⁰ Whether men and women require different ferritin reference intervals remains an open question. 

Practical Considerations

Two physician concerns merit attention. First, prior authorization requests for IV iron are frequently denied when ferritin values fall 1-2 µg/L above the stated lower limit, even in patients with clear iron deficiency. Second, raising the threshold too aggressively could drive unnecessary diagnostic testing, exposing patients to cost, risk, and anxiety without proven benefit.

Conclusion

On the Beckman platform, we are retaining the IFU-derived lower limit of 11 µg/L while adding an interpretive comment for results between 11 and 30 µg/L. This approach supports clinical decision-making while recognizing that no perfect solution currently exists. Members of the RCPA working group and international collaborators, including experts in the Netherlands, have submitted feedback to ASH regarding the lack of platform-specific considerations in the draft guidelines. Future clinical guidelines should explicitly account for inter-manufacturer assay variability to ensure consistent diagnosis and management of iron deficiency across different laboratory platforms.

References

1. Ko CW, Siddique SM, Patel A, et al. AGA clinical practice guidelines on the gastrointestinal evaluation of iron deficiency anemia. Gastroenterology. 2020;159(3):1085-1094.
2. Truong D, Hasan B, Pathak S, et al. Iron deficiency in adults: a review. JAMA. 2024;332(3):234-245.
3. Kodger J, El-Khoury J, Yurtsever N. Reevaluating Ferritin Reference Intervals: Defining Limits Based on Iron-Sufficient Population Studies, Clinical Relevance, and Healthcare Efficiency. J Appl Lab Med. 2026;11(1):193-196. doi:10.1093/jalm/jfaf151
4. Addison GM, Beamish MR, Hales CN, Hodgkins M, Jacobs A, Llewellin P. An immunoradiometric assay for ferritin in the serum of normal subjects and patients with iron deficiency and iron overload. J Clin Pathol. 1972;25(4):326-329.
5. Jacobs A, Miller F, Worwood M, Beamish MR, Wardrop CA. Ferritin in the serum of normal subjects and patients with iron deficiency and iron overload. Br Med J. 1972;4(5834):206-208.
6. Choy KW, Sezgin G, Wijeratne N, et al. Method-dependent differences in serum ferritin measurements and their impact on clinical decision-making. Pathology. 2022;54(3):307-313.
7. Braga F, Panteghini M. Commutability of reference materials and clinical chemistry results. Clin Chim Acta. 2022;525:54-59.
8. Pfeiffer CM, Looker AC. Laboratory methodologies for indicators of iron status: strengths, limitations, and analytical challenges. Am J Clin Nutr. 2017;106(Suppl 6):1606S-1614S.
9. Kurstjens S, van Dam AD, Oortwijn E, et al. Inconsistency in ferritin reference intervals across laboratories: a major concern for clinical decision making. Clin Chem Lab Med. 2024;63(3):600-610.
10. Troike C, McShane AJ. Redefining ferritin reference intervals: moving beyond sex-specific ranges. Clin Biochem. 2025;78:109-115.