Supplementary Material for: The role of hepcidin and an oral iron absorption test in identifying the root cause of iron-restricted anemia

Introduction: Traditional iron parameters often fail to distinguish the cause of iron-restricted anemia in patients without an obvious underlying cause. We evaluated whether an oral iron absorption test (OIAT) and hepcidin measurement could be useful diagnostic tests in these patients.

Methods: We retrospectively analyzed data extracted from medical records of all patients who underwent an OIAT and hepcidin measurement, noting subsequent clinical diagnosis. Δ iron >15 µmol/L during the OIAT and hepcidin level below the median (or suppressed ≤0.5 nM) were considered appropriate.

Results: Thirty-nine adult patients were included in the study. Sixteen patients with adequate OIAT had suppressed hepcidin levels indicative of classical iron-deficiency anemia (IDA); 59% of patients had abnormal OIAT. In this group, most patients with low hepcidin levels had anemia associated with abnormalities in the gastrointestinal tract, whereas 83.3% patients with high hepcidin levels had iron-refractory iron deficiency anemia (IRIDA), confirmed by genetic testing. Finally, transferrin/log ferritin ratio accurately identified patients with suppressed hepcidin: AUC 0.98 [95% CI: 0.95–1.02], P < 0.001.

Conclusion: OIAT differentiates between classical IDA and other types of anemia caused by abnormalities in iron absorption or systemic iron availability. Additionally, elevated hepcidin in patients with oral iron malabsorption could indicate IRIDA.

引言：传统铁参数往往难以区分无明确潜在原因的缺铁性贫血患者的病因。本研究旨在评估口服铁吸收试验（OIAT）和肝细胞素测量是否可作为此类患者的有用诊断试验。方法：我们对所有进行OIAT和肝细胞素测量的患者病历数据进行了回顾性分析，并记录了随后的临床诊断。在OIAT期间，铁Δ值大于15 µmol/L且肝细胞素水平低于中位数（或抑制≤0.5 nM）被视为适宜。结果：纳入研究的有39名成年患者。16名OIAT充足的患者的肝细胞素水平被抑制，表明经典缺铁性贫血（IDA）；59%的患者OIAT异常。在此组中，大多数肝细胞素水平低的患者与胃肠道异常相关的贫血相关，而83.3%肝细胞素水平高的患者有铁耐受性缺铁性贫血（IRIDA），经基因检测证实。最后，转铁蛋白/铁蛋白比准确识别了肝细胞素被抑制的患者：AUC 0.98 [95% CI: 0.95–1.02]，P < 0.001。结论：OIAT可区分经典IDA和其他由铁吸收或全身铁可用性异常引起的贫血类型。此外，口服铁吸收不良患者的肝细胞素升高可能表明IRIDA。