Measurement of serum transferrin receptor (sTfR) in critically ill patients

Introduction

Measurement of sTfR is an important new hematological parameter. Laboratory studies have indicated that sTfR values are elevated in anemias associated with enhanced erythropoiesis and tissue iron deficiency only. The aim of this study was to demonstrate whether iron deficiency, expressed through elevations of sTfR, constitutes an important etiologic component of ICU patients' anemia.

Methods

Twenty-seven patients were studied (10 male, 17 female), mean age 65.4 ± 4.0 years and mean APACHE II score of 16.5 ± 1.0. Five patients had sepsis syndrome, 12 severe sepsis, 8 had septic shock and 2 patients suffered from multiple organ failure. Patients who presented with a bleeding episode were excluded from the study. We measured sTfR, hemoglobin, hematocrit, serum iron concentration and ferritin and calculated APACHE II and sepsis score on day 1, 4 and 8 of ICU stay. For the measurement of sTfR, monoclonal antibodies were used.

Results

All critically ill patients had sTfR values at the lower level of the normal range (0.93 ± 0.5 mg/l, with normal values ranging between 0.94 and 1.28 mg/l). Though all sTfR values were found in the normal range, variations of transferrin receptors were correlated to sepsis score, hemoglobin and hematocrit on corresponding days. Statistical analysis revealed no significant difference.

Conclusion

Investigation of anemia in critically ill patients includes bone marrow examination for iron status determination. This invasive procedure can now be substituted by transferrin receptors' measurement, since ferritin levels are not reliable in septic patients, as it is the case with all acute phase proteins. Based on the above data, normal transferrin receptors in septic ICU anemic patients, indicate the minor role of iron deficiency in the aetiology of anemia in these patients, usually provides information on the etiology of anemia. Given that definitive distinction between iron deficiency anemia and the anemia of chronic disease requires a bone marrow examination to determine the iron status. To avoid the cost and discomfort of this method, measurement of sTfR can be used as a reliable index. In this study we observed that the iron deficiency anemia has low incidence in the critically ill patients.