Chiang W C, Tsai T J, Chen Y M, Lin S L, Hsieh B S
Department of Internal Medicine, En Chu Kong Hospital, Taipei County, Taiwan.
Clin Nephrol. 2002 Nov;58(5):363-9. doi: 10.5414/cnp58363.
The diagnosis of iron deficiency using the current commonly used tests is usually difficult in hemodialysis patients. Soluble transferrin receptor (sTfR) has caught the attention of physicians recently as regards its use as a parameter for the evaluation of iron status. This study was conducted in order to evaluate the correlation of serum soluble transferrin receptor (sTfR) concentration with hematological parameters and iron profiles, in the role of identifying iron deficiency among dialysis patients.
Seventy-three patients having received chronic hemodialysis and stable maintenance recombinant human erythropoietin (rHuEPO) therapy were included. Iron, total iron-binding capacity, ferritin and sTfR were measured in the first week. Following this, these patients began to receive intravenous iron dextran (2 mg/kg/week) for 4 weeks. The hematocrit (Hct), hemoglobin (Hb) levels and reticulocyte counts were evaluated weekly. At the beginning of fifth week, the sTfR level was measured again. Patients were classified as belonging to one of the following groups: serum ferritin < 100 microg/L - absolute iron-deficient group; initial ferritin level > or = 100 microg/L with an increase in hemoglobin of greater than 1 g/dL at the end of the study occult iron deficiency group; others - non iron-deficient group.
Seventy-one patients completed the study. The concentration of sTfR was positively correlated with Hct, Hb and reticulocyte index at the beginning (r = 0.236, p = 0.047; r = 0.257, p = 0.04; r = 0.401, p < 0.01, respectively) and at the end of the study (r = 0.384, p < 0.01; r = 0.338, p < 0.01; r = 0.427, p < 0.001, respectively). After 4 weeks of iron and rHuEPO therapy, the sTfR concentration increased, rather than declined, from 21.85 +/- 8.06 nM to 23.76 +/- 7.42 nM (p = 0.04) and the change was positively correlated with the changes in Hct, Hb and reticulocyte index. The administered rHuEPO doses did not differbetween the iron deficiency group (absolute deficiency, n = 3; occult deficiency, n = 10) and non-iron deficiency group (n = 58). The sTfR levels failed to identify the occult iron deficiency group because there was no difference between occult iron-deficient and non-iron-deficient patients (24.73 +/- 9.09 nM versus 21.60 +/- 7.89 nM, p = 0.34). Instead, transferrin saturation (TS) could be a differential marker between the 2 groups (19.0 +/- 10.9% versus 30.1 +/- 12.7%, p = 0.012).
The serum sTfR concentration is indeed an appropriate marker for erythropoiesis. The erythropoitic effect of administered rHuEPO could mask the effect of iron status on the sTfR concentration. This might make the sTfR concentration no longer an appropriate index to identify the presence of occult iron deficiency. Thus, TS and ferritin currently remain better methods for the evaluation of iron status in rHuEPO-treated chronic hemodialysis patients.
对于血液透析患者，使用当前常用检测方法诊断缺铁通常较为困难。可溶性转铁蛋白受体（sTfR）作为评估铁状态的参数，近来引起了医生们的关注。本研究旨在评估血清可溶性转铁蛋白受体（sTfR）浓度与血液学参数及铁指标之间的相关性，以确定其在透析患者缺铁诊断中的作用。
纳入73例接受慢性血液透析且维持重组人促红细胞生成素（rHuEPO）治疗稳定的患者。在第一周测定铁、总铁结合力、铁蛋白和sTfR。此后，这些患者开始接受静脉注射右旋糖酐铁（2mg/kg/周），共4周。每周评估血细胞比容（Hct）、血红蛋白（Hb）水平和网织红细胞计数。在第五周开始时，再次测定sTfR水平。患者被分为以下组之一：血清铁蛋白<100μg/L - 绝对缺铁组；初始铁蛋白水平≥100μg/L且研究结束时血红蛋白升高大于1g/dL - 隐匿性缺铁组；其他 - 非缺铁组。
71例患者完成了研究。sTfR浓度在研究开始时（分别为r = 0.236，p = 0.047；r = 0.257，p = 0.04；r = 0.401，p < 0.01）和结束时（分别为r = 0.384，p < 0.01；r = 0.338，p < 0.01；r = 0.427，p < 0.001）与Hct、Hb和网织红细胞指数呈正相关。经过4周的铁和rHuEPO治疗后，sTfR浓度从21.85±8.06nM增加至23.76±7.42nM，而非下降（p = 0.04），且该变化与Hct、Hb和网织红细胞指数的变化呈正相关。缺铁组（绝对缺铁，n = 3；隐匿性缺铁，n = 10）和非缺铁组（n = 58）之间给予的rHuEPO剂量无差异。sTfR水平未能识别隐匿性缺铁组，因为隐匿性缺铁患者和非缺铁患者之间无差异（24.73±9.09nM对21.60±7.89nM，p = 0.34）。相反，转铁蛋白饱和度（TS）可能是两组之间的鉴别标志物（19.0±10.9%对30.1±12.7%，p = 0.012）。
血清sTfR浓度确实是红细胞生成的合适标志物。给予的rHuEPO的促红细胞生成作用可能掩盖了铁状态对sTfR浓度的影响。这可能使sTfR浓度不再是识别隐匿性缺铁存在的合适指标。因此，目前TS和铁蛋白仍是评估接受rHuEPO治疗的慢性血液透析患者铁状态的更好方法。
