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：对于无明确潜在病因的铁限制性贫血患者，传统铁代谢指标往往难以明确其发病诱因。本研究旨在评估口服铁吸收试验（oral iron absorption test, OIAT）与铁调素（hepcidin）检测是否可作为此类患者的有效诊断手段。
方法：本研究回顾性分析了所有接受OIAT与铁调素检测的患者的病历提取数据，并记录其后续临床诊断结果。将OIAT检测中血清铁变化量Δ iron＞15 µmol/L，以及铁调素水平低于中位数（或被抑制至≤0.5 nM）判定为结果合格。
结果：本研究共纳入39名成年患者。其中16例OIAT结果合格的患者铁调素水平受抑，符合经典缺铁性贫血（iron-deficiency anemia, IDA）的特征；59%的患者OIAT结果异常。在该亚组中，铁调素水平低下的患者多伴发胃肠道异常相关性贫血，而83.3%铁调素水平升高的患者经基因检测证实为难治性缺铁性贫血（iron-refractory iron deficiency anemia, IRIDA）。最终，转铁蛋白/对数铁蛋白比值可准确识别铁调素受抑的患者：曲线下面积（area under curve, AUC）为0.98 [95%置信区间（confidence interval, CI）：0.95~1.02]，P＜0.001。
结论：OIAT可有效区分经典缺铁性贫血与铁吸收异常或机体铁利用异常所致的其他类型贫血。此外，口服铁吸收不良患者的铁调素水平升高，可提示难治性缺铁性贫血的可能。