Hypochromic reticulocytes, hypochromic erythrocytes and p-transferrin receptors in diagnosing iron-deficient erythropoiesis

Plasma vitamin C levels in ESRD patients and occurrence of hypochromic erythrocytes

INTRODUCTION

The achievement of erythropoiesis in hemodialysis (HD) patients is typically managed with erythropoiesis-stimulating-agents (ESA's) and intravenous iron (IV-iron). Using this treatment strategy, HD patients frequently show an elevated fraction of red blood cells (RBC) with hemoglobin (Hb) content per cell that is below the normal range, called hypochromic RBC. The low Hb content per RBC is the result of the clinical challenge of providing sufficient iron content to the bone marrow during erythropoiesis. Vitamin C supplements have been used to increase Hb levels in HD patients with refractory anemia, which supports the hypothesis that vitamin C mobilizes iron needed for Hb synthesis.

METHODS

We conducted a cross-sectional survey in 149 prevalent HD patients of the percent hypochromic RBC, defined as RBC with Hb < 300 ng/uL of packed RBC, in relation to plasma vitamin C levels. We also measured high-sensitivity CRP, (hs-CRP), iron, and ferritin levels. and calculated ESA dose.

FINDINGS

High plasma levels of vitamin C were negatively associated with hypochromic RBC (P < 0.003), and high ESA doses were positively associated (P < 0.001). There was no significant association of hs-CRP with percent hypochromic RBC.

DISCUSSION

This finding supports the hypothesis that vitamin C mobilizes iron stores, improves iron delivery to the bone marrow, and increase the fraction of RBC with normal Hb content. Further research is warranted on development of protocols for safe and effective use of supplemental vitamin C for management of renal anemia.

Serum hepcidin-25 in comparison to biochemical markers and hematological indices for the differentiation of iron-restricted erythropoiesis

BACKGROUND

Biochemical markers have problems in distinguishing iron deficiency anemia (IDA) from anemia of chronic disease (ACD), and the combined state of iron-restricted erythropoiesis (IRE) with ACD (ACD/IRE). We investigated the extent to which hepcidin-25, a potential marker for the evaluation of iron metabolism, enables the differentiation of the states above, and to assess its correlation with convential markers of iron deficiency.

METHODS

One hundred and fifty-five patients with anemia were classified as having IDA, ACD or ACD/IRE using clinical findings, biochemical markers and hematological indices. The diagnostic performance of hepcidin-25 alone or in combination with the reticulocyte hemoglobin content (CHr) was evaluated using receiver-operating characteristic curve analysis and multivariate analysis. Hepcidin-25 was determined using an isotope-dilution micro-HPLC-tandem mass spectrometry method.

RESULTS

Hepcidin-25 correlated with biochemical markers of iron deficiency but not with hematological indices. Use of a hepcidin-25 cut-off of ≤ 4 nmol/L allowed the differentiation of IDA from ACD and ACD/IRE, but not the discrimination of ACD from ACD/IRE in patients with severe inflammation. Furthermore, the discrimination of ACD/IRE from ACD required the combination with CHr.

CONCLUSIONS

Hepcidin-25 is primarily an indicator for decreased body iron levels, but not for IRE. The combination of hepcidin-25 with CHr in a diagnostic plot (hepcidin-25 plot) might be useful for the differentiation of ACD from ACD/IRE and IDA.

Reticulocytes in sports medicine

Reticulocytes are the transitional cells from erythroblasts to mature erythrocytes. Reticulocytes are present in blood for a period of 1-4 days and can be recognized by staining with supravital dyes, such as new methylene blue, or fluorescent markers, which couple residual nucleic acid molecules, a hallmark of the immature forms of erythrocytes. Although reticulocytes could be counted through a microscope (there is a standard of International Committee for Standardisation in Haematology for manual counting), this method is reported to be time consuming, inaccurate and imprecise. The integration of the reticulocyte count in automated haematology systems allowed the widespread use of these parameters, although the lack of calibration material and different markers, technologies and software used in automated systems could engender discrepancies among data obtained from different analytical systems.The importance of reticulocytes in sports medicine derives from their sensitivity, the highest among haematology parameters, in identifying the bone marrow stimulation, especially when recombinant human erythropoietin is fraudulently used. Automated systems are also able to supply information on volume, density and the haemoglobin content of reticulocytes. Some of the related parameters are also used in algorithms for identifying abnormal stimulation of bone marrow as reticulocytes haematocrit. The pre-analytical variability of reticulocytes (transportation, storage, biological variability) should be taken into account in sports medicine also. Reticulocytes remain stable for almost 24 hours at 4 degrees C from blood drawing, they are affected by transportation, and biological variability is not high in general. It could be remarked, however, that the intra-individual variability is high when compared with other haematological parameters such as haemoglobin and haematocrit. The intervals of data reported in athletes are very similar to reference intervals characterizing the general population.The reticulocyte count shows some modifications after training and during the competition season. The variability induced by exercise cannot be overlooked since the so-called haematological passport, a personal athlete's document in which haemoglobin and other parameters are registered, may be introduced by sports federations. Exposure to naturally high altitude and 'living high-training low' programmes determined contentious results on reticulocytes. Simulated high altitude induced by intermittent hypobaric hypoxia does not modify reticulocytes, despite an increase in erythropoietin serum concentration. The variability among athletes competing in different sport disciplines is apparently limited. The knowledge of the behaviour of reticulocytes in training and competitions is crucial for defining their role in an antidoping control context. It is important for sport physicians and clinical pathologists to know the reticulocyte variability in the general population and in athletes, the pre-analytical warnings, the different methodologies for counting reticulocytes and the derived parameters automatically available, and, finally, the possible influence of training, competitions, type of sport and altitude.

Blood transfusions in athletes. Old dogmas, new tricks

Blood doping consists of any illicit means used to increase and optimize oxygen delivery to the muscles and includes blood transfusions, administration of erythropoiesis-stimulating substances, blood substitutes, natural or artificial altitude facilities, and innovative gene therapies. The use of blood transfusion, an extremely straightforward, practical and effective means of increasing an athlete's red blood-cell supply in advance of competition, became rather popular in the 1970s, but it has suddenly declined following the widespread use of recombinant human erythropoietin among elite endurance athletes. Most recently, following implementation of reliable tests to screen for erythropoiesis-stimulating substances, blood transfusions have made a strong resurgence, as attested by several positive doping tests. Doping by blood transfusion can be classified as homologous, where the blood is infused into someone other than the donor, and autologous, where the blood donor and transfusion recipient are the same. The former case produces more clinically relevant side effects, but is easily detectable using current antidoping protocols based on erythrocyte phenotyping by flow cytometry and, eventually, erythrocyte genotyping by DNA testing. Since the donor and recipient blood are identical in autologous blood doping, this is less risky, though much more challenging to detect. Indirect strategies, relying on significant deviations from individual hematological profiles following autologous blood donation and reinfusion, are currently being investigated. For the time being, the storage of athletes' blood samples to allow testing and sanctioning of guilty athletes once a definitive test has been introduced may represent a reliable deterrent policy.