Evaluation of serum iron in hemodialysis patients and its variation due to the difference of blood sampling time

Diurnal variations in serum iron concentration were examined to investigate the influence of sampling time in hemodialysis (HD) patients and healthy subjects. The serum iron concentration and TIBC of HD patients decreased significantly (p<0.01, p<0.01 respectively) compared to those of healthy subjects. Inversely, the serum ferritin concentration of HD patients increased significantly (p<0.01) compared to that of healthy subjects. These findings show the disturbance of iron transport system: under such condition intracellural iron transition out into peripheral blood stream is low in HD patients. Serum iron concentration in samples collected in the evening decreased significantly both in HD patients (p<0.05) and in healthy subjects (p<0.01). Diurnal variations in serum iron concentration reveal almost similar decrement in both groups. In HD patients, serum iron concentration of the blood samples collected on the third day morning after HD and second day morning after HD was examined to see the influence from changes of circulating plasma volume. The serum iron concentration and Hct value in the second day sampling increased significantly compared to the third day sampling (p<0.01, p<0.01 respectively). In addition, the serum iron concentration corrected by Hct in the second day sampling increased significantly (p<0.01) compared to the third day sampling. We conclude from our results that diurnal variations of serum iron concentration vary in sampling time in HD patients as well as in healthy subjects. We also deduct that there may be other factors concerning changes in circulating plasma volume.