Evaluation of the Sysmex R-1000. An automated reticulocyte analyzer

Reticulocytosis and anemia are associated with an increased risk of death and stroke in the newborn cohort of the Cooperative Study of Sickle Cell Disease

Prior analyses of the Cooperative Study of Sickle Cell Disease (CSSCD) newborn cohort identified elevated white blood cell (WBC) count, low baseline hemoglobin and dactylitis between the ages of 1 and 2 years as markers of severe disease. Reticulocytosis was also associated with severe disease. Here, we further analyzed data collected on enrolled CSSCD infants for the predictive value of those markers for stroke and death later in life. Three hundred fifty-four CSSCD subjects were identified who had absolute reticulocyte counts (ARC) measured during infancy (2 to 6 months of age). Infants with higher ARC had significantly increased risk of stroke or death during childhood; lower hemoglobin levels also increased the risk but to a lesser degree than ARC. WBC levels and dactylitis were not predictive of death or stroke. These data suggest that reticulocytosis among asymptomatic infants with sickle cell anemia is associated with an increased risk of death or stroke during childhood.

Quality assurance in clinical laboratories. An updated supplement to a bibliography

A supplement to a bibliography (Scand J Clin Lab Invest 1987;47 suppl. 187:1-96) dealing with quality assurance in the clinical laboratory is presented. The increasing role of national and international standardizing bodies is stressed as well as implementation of rules of "good laboratory practice". Objectively established quality goals for all services is highly needed in order to provide a rationale for the efforts dedicated to quality improvements. Quality goals for many clinical chemistry and haematology investigations are now available.

A biparametric flow cytometry analysis for the study of reticulocyte patterns of maturation

Automated haematological analysers still represent the gold standard for the study of reticulocyte maturation even if this technique is based on structural properties and staining affinity rather than on functional aspects. On the contrary, flow cytometry allows the simultaneous analysis of multiple cellular characteristics including functional features. Aim was to investigate whether simultaneous analysis of different reticulocyte parameters using flow cytometry may add functional information when considering their pattern of maturation. Thirty-nine healthy donors (H) and 31 haemodialysed patients on treatment with rHuEpo (HDT) were analysed. Reticulocyte counts and their stages of maturation were studied both with ADVIA 2120 and by flow cytometry. TO/CD71 scattergraph reticulocyte analysis designed a peculiar distribution which was similar among the same group of subjects (H or HDT), but different between H and HDT. distribution of the percentage of reticulocytes in low, medium and high boxes calculated by ADVIA 2120 did not show any difference between H and HDT groups, while the analysis using flow cytometry pointed out statistically significant differences between H and HDT groups in the three boxes where the TO+/CD71+ reticulocytes were localized. The present study suggests that TO/CD71 analysis was reproducible and could detect different pattern of maturation of a particular clinical setting.

Characterization of the myelotoxicity of chloramphenicol succinate in the B6C3F1 mouse

Chloramphenicol (CAP) is haemotoxic in man, inducing two types of toxicity. First, a dose-related, reversible anaemia with reticulocytopenia, sometimes seen in conjunction with leucopenia and thrombocytopenia; this form of toxicity develops during drug treatment. The second haemotoxicity is aplastic anaemia (AA) which is evident in the blood as severe pancytopenia. AA development is not dose-related and occurs weeks or months after treatment. We wish, in the longer term, to investigate CAP-induced AA in the busulphan-pretreated mouse. However, as a prelude to that study, we wanted to characterize in detail the reversible haemotoxicity of CAP succinate (CAPS), administered at high dose levels in the mouse, and follow the recovery of the bone marrow in the post-dosing period. Female B6C3F1 mice were gavaged with CAPS at 0, 2500 and 3500 mg/kg, daily, for 5 days and sampled (n = 5) at 1, 7, 14 and 21 days post-dosing. Blood, bone marrow and spleen samples were analysed and clonogenic assays carried out. At day 1 post-dosing, at both CAPS dose levels, decreases were seen in erythrocytes and erythrocyte precursors; marrow erythroid cells were reduced. Reductions were also evident in splenic nucleated cell counts, blood high fluorescence ratio (HFR) reticulocyte counts and total reticulocyte counts; burst-forming units-erythroid and colony-forming units-erythroid showed decreases. At day 7 post-dosing (2500 mg/kg CAPS), there was regeneration of erythrocyte production, with marked splenic erythropoietic activity, and raised blood HFR reticulocytes. At day 7, at 3500 mg/kg CAPS, erythrocyte and reticulocyte parameters remained depressed. At 14 days post-dosing (2500 mg/kg CAPS), many erythrocyte parameters had returned to normal; at 3500 mg/kg CAPS, there was erythroid regeneration. By 21 days post-dosing, at both CAPS dose levels, most erythrocytic parameters were equivalent to control values. For leucocyte parameters, there was some depression at day 1 post-dosing (at both CAPS dose levels) and signs of recovery at day 7. At days 14 and 21 post-dosing, most leucocyte parameters were close to control values. Marrow smears at day 1 post-dosing (at both CAPS dose levels) showed vacuolation of early normoblasts, of myeloid and of monocytic precursors. We conclude that the administration of CAPS at 2500 and 3500 mg/kg for 5 days induced significant myelotoxicity in female B6C3F1 mice, with cessation of erythropoiesis at day 1 post-dosing; recovery was seen over the following 7/14 days. The blood HFR reticulocyte count was a precise indicator of CAPS-induced depressive effects and subsequent recovery. It is concluded that the administration of five daily doses of CAPS at 2500 and 3500 mg/kg to the female B6C3F1 mouse induces an anaemia with reticulocytopenia, in conjunction with leucopenia, in the immediate post-dosing period; no evidence was seen at 21 days post-dosing of peripheral blood pancytopenia or a hypocellular/acellular bone marrow, which are both characteristic features of AA in man.

Automated analyzer evaluation of reticulocytes in bone marrow and peripheral blood of hematologic disorders

The R-3000 reticulocyte analyzer uses flow cytometry with an argon laser as its light source. This analyzer stains residual RNA with auramine O to provide a reticulocyte maturation differential. Using the R-3000, we analyzed 119 samples of bone marrow (BM) and peripheral blood (PB) from 111 patients with hematologic disorders. Parameters were reticulocytes, immature reticulocyte fraction (IRF) percentage in BM and PB, BM/PB reticulocyte ratio, and BM/PB IRF ratio. Reticulocytes and IRF percentage in BM were significantly higher than in PB (p < 0.01). There was also a good correlation between reticulocyte percentages in BM and in PB (r = 0.81). Patients were classified into a normal group (without anemia) and an anemia group. Furthermore, the anemia group was classified into three groups: group 1: cases with hematopoietic dysfunction; group 2: cases in bone marrow recovery phase after chemotherapy and hematopoietic stem cell transplantation, and hematologic disorders with bone marrow accelerative phase, and group 3: cases with ineffective hematopoiesis (myelodysplastic syndrome). The mean reticulocyte percentage of the normal group was 2.3 +/- 1.1%, which was close to the normal value in BM. The BM/PB reticulocyte ratio of group 3 was statistically higher than that of groups 1 and 2. This indicates that group 3 had ineffective erythropoiesis and that the BM/PB ratio is a useful indicator for the diagnosis of myelodysplastic syndrome.

Reticulocyte analysis by flow cytometry and other techniques

Enumeration of peripheral blood reticulocytes is an essential part of the diagnosis and management of anemic patients, since the number of reticulocytes in the peripheral blood reflects the erythrocytic activity of the bone marrow. Reticulocyte enumeration using flow cytometric methodology is rapidly replacing the inaccurate, imprecise manual counting technique used in the past. This article explores the pathophysiology of the reticulocyte, the various means of counting reticulocytes, and the diverse clinical applications of reticulocyte data.

New quantitative parameters on a recently introduced automated blood cell counter--the XE 2100

The XE 2100 (Sysmex Corporation) is a cell counter that furthers the technology of fluorescent flow cytometry developed from the earlier range of Sysmex analysers. The new diagnostic features are a nucleated red cell count (NRBC), the ability to measure platelets by impedance as well as an 'optical' platelet count using a fluorescence dye and an immature granulocyte (IG) count. The NRBC count was highly correlated (r = 0.97) with the manual reference count. For counts below 100 x 109/l the 'optical' method and the immunocount gave good a correlation (r = 0.97) optical and impedance counts were also well correlated (r = 0.89). The use of the 'optical' platelet count significantly improves the reliability of low platelet counts. The IG count correlated with visual counts (r = 0.81) and allows the detection of immature cells at an earlier stage in the laboratory process. The introduction of fluorescent flow cytometric analysis allows extended quantification of additional cell populations and so potentially improves screening and monitoring of various pathological conditions.

Reticulocyte cellular indices: a new approach in the diagnosis of anemias and monitoring of erythropoietic function

Reticulocyte analysis has been extended from the simple enumeration of reticulocytes to precise measurements of mRNA content and of cellular indices such as volume, hemoglobin (Hb) concentration, and content. Assessment of reticulocyte maturity is based on the fluorescence intensity of reticulocytes, which depends on RNA content. The appearance of high fluorescence reticulocytes has been shown to be associated with engraftment in the setting of bone marrow or peripheral stem cells transplantation, although it is still not clear how this parameter can improve quality or cost of care compared with the traditional use of absolute neutrophil counts. Reticulocyte indices have been studied especially in the setting of iron deficiency and functional iron deficiency during recombinant human erythropoietin (r-HuEPO) therapy. Reticulocyte hemoglobin content (CHr) may allow prompt identification of an imbalance between r-HuEPO therapy and iron availability by detecting the presence in reticulocytes of iron-restricted erythropoiesis. Diagnosis of simple iron deficiency can also be achieved in a more cost-effective fashion by using CHr in conjunction with the regular complete blood count (CBC), rather than relying on the traditional biochemical parameters of iron metabolism. Response to therapy of megaloblastic anemia can also be monitored with CHr. These new reticulocyte parameters provide a real-time assessment of the functional state of erythropoiesis.

Determination of reticulocytes: three methods compared

Determination of reticulocytes in peripheral blood is a valuable tool for getting information about erythropoiesis of an individual. For many years, reticulocyte numbers were quantified manually by means of a microscope after staining with supravital dyes. However, this method is tedious and shows low reproducibility. Therefore, several methods for the automated determination of reticulocytes have been established in laboratory routine within the last years. The aim of this study was to compare three of these automated methods for reticulocyte analysis. Reticulocytes were determined in 130 subsequent routine samples by means of an ABX Pentra 120 Retic haematological analyser, a Coulter EPICS XL MCL flow cytometer and a Coulter STKS haematology system, using the fluorescent dye thiazole orange or the supravital dye new methylene blue for reticulocyte staining, respectively. The reticulocyte concentrations were slightly lower for the Coulter STKS haematology system (mean +/- SD 1.89+/-1.32%) when compared with the Coulter EPICS XL MCL flow cytometer or the ABX Pentra 120 Retic haematological analyser (2.11+/-1.25% and 2.12+/-1.15%, respectively). The correlations between all methods were significant (r(s) > or = 0.843, p < 0.001). Small intercepts were, however, observed in the correlation plots between the values obtained by means of the Coulter STKS haematology system and those obtained by the other two methods. Within-batch coefficients of variation were 6.0%, 6.9% and 7.8% for the ABX Pentra 120 Retic haematological analyser, the Coulter STKS haematology system and the Coulter EPICS XL MCL flow cytometer, respectively. The corresponding between-batch coefficient of variation values were 6.8%, 4.9% and 5.3% as well as 14.1%, 7.6% and 6.1% for the low, medium and high control levels determined by means of the ABX Pentra 120 Retic haematological analyser and the Coulter STKS haematology system, respectively. These data suggest that all three methods allow the efficient and reliable determination of reticulocyte counts under clinical routine conditions. However, although the obtained data are very similar, differences exist which should be taken into account for the normal values of the different methods.

Hemoglobin switching protocols in thalassemia. Experience with sodium phenylbutyrate and hydroxyurea

Homozygous beta thalassemia affects thousands of people around the world. Current management of this condition includes regular transfusion of red cells, which leads to transfusional iron overload requiring chelation therapy: increasing hemoglobin levels while decreasing or eliminating iron overload is therefore a major therapeutic goal in the treatment of thalassemia. Bone marrow transplantation may achieve this goal, but it is not an option for most patients. This study reports on efforts to increase gamma-globin transcription and HbF production using sodium phenylbutyrate (SPB) and hydroxyurea (HU). It was found that 36% (4/11) of all patients or 50% (4/8) of non-transfused patients responded to SPB (increase in Hb levels of 1 g/dL). A positive correlation between baseline serum erythropoietin level and likelihood of response to SPB was observed. Since HU may also increase HbF production, evaluation of combination therapy with these drugs is underway and preliminary results are reported.

Use of reticulocyte cellular indices in the diagnosis and treatment of hematological disorders

Automated counting of reticulocytes has markedly increased the precision and accuracy of this assay compared with the traditional manual counts. In addition, several new reticulocyte parameters are now available to clinicians and pathologists. This review examines the potential role of these parameters in the diagnosis and management of anemias. Reticulocyte maturity can now be assessed based on the staining intensity of reticulocytes, which is proportional to their RNA content. However, the clinical value of the numerical estimate of the immature reticulocyte fraction has not been yet demonstrated. In the bone marrow transplant setting, there is no clear evidence that the use of this index results in improved care of these patients, and many studies have failed to show its superiority compared with the traditional white cell count, especially for autologous transplants. Direct measurement of reticulocyte volume, hemoglobin concentration, and hemoglobin content are now available. Studies have shown that these parameters, and hemoglobin content in particular, allow a real-time assessment of the functional state of the erythroid marrow. In the setting of recombinant human erythropoietin therapy, studies of hemoglobin content have shown that this index allows an early detection of functional iron deficiency. Preliminary studies have also shown that this index may be helpful in the diagnosis of iron deficiency and in the monitoring of iron replacement therapy.

Reticulocytes and reticulated platelets: simultaneous measurement in whole blood by flow cytometry

Reticulated platelets are a fraction of newly released circulating elements characterized by a residual amount of RNA. It has been suggested that the reticulated platelet count, providing an estimate of thrombopoiesis in the same way as erythrocyte reticulocyte count is a measure of erythropoiesis, may be useful in the study of thrombocytopenic disorders. Reticulated red cells and platelets can be analyzed by flow cytometry using specific stains for nucleic acids such as Thiazole Orange and Auramine-O. The aim of our work was to perform the simultaneous evaluation of reticulated elements in whole blood using a standard flow cytometer and to correlate the results obtained with a dedicated cytometer. A group of 14 patients with abnormal absolute reticulocyte counts (range 1.1-11%) and a group of 41 patients showing a platelet discrimination error when analyzed with a dedicated flow cytometer (Sysmex R1000) were enrolled. Linear amplification of both scatter and fluorescence was used to perform reticulocyte count. A gate was set on platelet dimensions, and logarithmic amplification of scatter and fluorescence was used to count reticulated platelets. A good correlation was obtained both for results of reticulocyte count (r2 = 0.9825) and for reticulated platelets (r2 = 0.8717) between our method and those using dedicated instruments. These data show that reticulated platelet count may be easily introduced in clinical laboratories that routinely perform reticulocyte count by flow cytometry.

Reticulocyte hemoglobin content in the evaluation of iron status of hemodialysis patients

The assessment of iron status for hemodialysis patients has been hindered by the inaccuracy of commonly used diagnostic tests. A novel assay, the reticulocyte hemoglobin content (CHr), has recently been found to sensitively detect functional iron deficiency among nonuremic patients treated with recombinant erythropoietin (rHuEPO). The purpose of this study was to evaluate the CHr for the assessment of iron status in hemodialysis patients. One hundred sixty-four stable hemodialysis patients had a mean CHr of 27.5 +/- 2.8 pg with a normal distribution of values. The mean CH (mature red cell hemoglobin content) was 26.4 +/- 2.4 pg. There was a close correlation between CHr and CH (r = 0.86, P < 0.0001). A significant subgroup of patients (12.2%) had CHr values < CH. These patients had recent increases in rHuEPO dose, and a lower mean transferrin saturation and hematocrit, suggesting the recent onset of functional iron deficiency due to the increase in rHuEPO dose. In the second phase of the study, 32 patients were randomly selected to receive treatment with a single dose infusion of 1,000 mg of intravenous iron dextran (IVFe). Patients were classified as iron deficient (N = 7) if they responded with a significant reticulocytosis (sustained 1 basis point increase in corrected reticulocyte index within 2 weeks). All other patients were classified as iron replete (N = 25). A CHr < 26 pg at baseline predicted iron deficiency with a sensitivity of 100%, specificity of 80%. The serum ferritin, transferrin saturation and percentage of hypochromic red blood cells all were less accurate. The time to correction of iron deficiency at the level of the reticulocyte was found to be within 48 hours as measured by correction of the mean CHr to > 26 pg, and by the shift of the vast majority of the reticulocyte population to CHr > 26 pg within this time span. We conclude that CHr < 26 pg is an accurate measure of iron status in hemodialysis patients, that a CHr value < CH indicates the acute onset of iron deficiency, and that a single dose infusion of intravenous iron results in correction of iron deficiency at the level of the reticulocyte within 48 hours.

The effect of GM-CSF on reticulocytes, haemoglobin and haematocrit in patients receiving chemotherapy for solid tumours

The effect of granulocyte-macrophage colony stimulating factor (GM-CSF) on reticulocytes, haemoglobin and haematocrit levels of patients receiving chemotherapy for solid tumours was assessed. Forty-two patients were randomized into two groups who either did or did not receive GM-CSF 300 U/d on days 8 and 15 post-chemotherapy for neutropenia prophylaxis. Patients were stratified according to tumour type (non small-cell lung cancer, small-cell lung cancer, ovarian and breast cancer). Eight patients with progressive disease were excluded. The 34 patients evaluated completed six chemotherapeutic cycles of 21 days. They did not receive transfusions or erythropoietin. The estimated dose intensities (mg/m2/d) for each drug used were significantly higher in the group on GM-CSF compared to the group without. Haemoglobin and haematocrit were measured by the H * 1 (Bayer) haematology analyser and reticulocyte counts by the flow-cytometric reticulocyte analyser, R-1000 (Sysmex). Measurements were conducted on days 1 and 12 of every cycle for six cycles. At the beginning of therapy there were no significant differences between the two groups. However, red cell and reticulocyte counts fell significantly in the group without GM-CSF compared to the group on GM-CSF. Reticulocyte differences preceded those of haemoglobin and haematocrit. The data indicate a positive in vivo effect of GM-CSF on the erythroid tissue of patients receiving chemotherapy for solid tumours.

Filterability of mixtures of sickle and normal erythrocytes

We investigated the deformability of sickle (SS) cells from 25 patients and mixtures of these SS cells with blood type-compatible normal (AA) cells, using a nickel mesh filtration system, with the aim of determining optimal goals for exchange therapy. We found that for air-equilibrated SS/AA cell mixtures the fraction of dense cells (MCHC > 37 g/dl) is the determinant factor in filterability and that the dense cells contribute in a linear fashion to the loss of filtration up to 15% dense cells (y = -4.41x + 98.23, r = 0.945, P < 0.0001). The slope of this effect is approximately 25 times steeper than that of the relationship between filtration and percent nondense (MCHC < 37/g/dl) SS cells (y = -0.17x + 106.53, r = 0.772, P < 0.0001). A comparison of the proportion of high fluorescence reticulocytes to total reticulocytes (HFR ratio), indicating an elevation of immature reticulocytes, between six nontransfused patients and six exchange-transfused patients showed significant higher values in the nontransfused individuals (0.154 +/- 0.051 versus 0.070 +/- 0.054, P < 0.003). These results may have implications regarding targets for exchange transfusion therapy. Further studies of the effect on transfusion, both simple and exchange, on the numbers of dense cells and the proportions and populations of reticulocytes and the rheological characteristics of the erythrocyte subpopulations seems warranted.

Flow cytometer and imaging device used in combination

This report presents a flow cytometer devised by the authors and equipped with a CCD camera to obtain images of selected particles. Each image is linked to a point in the scattergram from which it can be retrieved from memory. The system uses an argon ion laser for flow-cytometric analysis and a diode-pumped pulse laser (532nm) to generate CCD images. Aggregated platelets in a blood sample and casts in a urine sample can be detected by this system. A fast flow rate is suitable for efficient flow-cytometric detection, and image resolution is sufficiently adequate for recognizing aggregated platelets and casts. Flow-cytometric and morphological data are used together to distinguish different types of cells in the same region on the scattergram and identify cells present in extremely small numbers among the majority.

Flow cytometric reticulocyte maturity index: a useful laboratory parameter of erythropoietic activity in anemia

Flow cytometric reticulocyte analysis is superior to manual reticulocyte counting with respect to precision and sensitivity. Furthermore, because the fluorescence intensity of reticulocytes is directly proportional to the erythrocyte RNA content, flow cytometric analysis using thiazole orange gives a quantitative reticulocyte maturity index (RMI). Previous studies have demonstrated that the RMI parameter is the earliest indicator of bone marrow engraftment following transplantation. In the present study, we analyzed the correlation of the RMI to standard red cell parameters, reticulocyte percentage, and absolute reticulocyte count in 413 anemic patients. The correlation of RMI to serum erythropoietin (Epo) and serum transferrin receptor (TfR) was analyzed in a subset of anemic blood samples. We found weak correlations between the RMI and hemoglobin (r2 = 0.041), hematocrit (r2 = 0.038), reticulocyte percentage (r2 = 0.078), and absolute reticulocyte count (r2 = 0.087). Stronger correlations were observed between the RMI and Epo (r2 = 0.181) and the TfR (r2 = 0.191). The results indicate that the RMI represents a cost-effective measurement of erythropoietic activity and provides an additional parameter to classify anemic patients into categories of high and low erythropoietic activity, especially in hypoproductive anemias.

Automated measurement of reticulated platelets in estimating thrombopoiesis

We described a fully automated measurement of reticulated platelets using a fluorescent dye, auramine O, and a reticulocyte counter, the R-3000, equipped with special software. Reproducibility and linearity were shown to be good. In the normal subjects studied (n = 60), the mean value for reticulated platelets was 0.98% +/- 0.41% and the mean absolute count was 2.12 +/- 0.69 x 10(9)/l. The absolute count for reticulated platelets was significantly lower (p < 0.05) in patients with reduced thrombopoiesis as seen in acute myeloblastic leukemia, aplastic anemia or chemotherapy-induced thrombocytopenia and it was elevated (p < 0.05) in essential thrombocythemia and in chronic myelocytic leukemia with thrombocytosis. All 20 patients with chronic idiopathic thrombocytopenic purpura had a high percentage of reticulated platelets. The percentage of reticulated platelets was significantly increased (p < 0.05) in patients with impaired thrombopoiesis despite the reduction in the absolute count. In 2 leukemic patients, an apparent rise was noticed in the percentage of reticulated platelets which preceded by several days a progressive increase in the platelet count at the recovery phase of thrombocytopenia. The results suggest that an automated measurement of reticulated platelets can be applied to routine laboratories for clinical use.

Methodology-dependent variations in reticulocyte counts using a manual and two different flow cytometric procedures

This paper describes a comparison between the microscopic brilliant cresyl blue and the flow cytometric thiazol orange (FACScan) and auramine O (Sysmex) methods for enumeration of reticulocytes. The mean intra-assay coefficients of variation for the microscopic, FACScan and Sysmex methods were established to be 33.9 and 5% respectively. A rather poor correlation was observed between the microscopic count and both flow cytometric methods (FACScan r = 0.61; Sysmex r = 0.57). However, the correlation between the flow cytometric methods was satisfactory (r = 0.79). Reference ranges for the reticulocyte count, corresponding with the 2.5th and 97.5th percentile, were determined for the microscopic (8-30/1000), FACScan (11-27/1000) and Sysmex (8-18/1000) methods. Sysmex R-3000 methodology definitely revealed the lowest and narrowest reference range. In conclusion, because of higher reproducibility, flow cytometric analysis of reticulocytes is an attractive alternative procedure for the microscopic enumeration method.

Reticulocyte maturity pattern analysis as a predictive marker of erythropoiesis in paediatrics. Part I: Evaluation of age-dependent reference values

Reticulocyte quantification in peripheral blood samples is a commonly used diagnostic indicator of erythropoietic activity. A methodology based on flow cytometry additionally separates reticulocytes into three groups by fluorescence staining of the residual RNA. This identifies cells as high (HFR), medium (MFR) and low (LFR) fluorescence intensity reticulocytes. In the present study an automated counter was evaluated and tested for its clinical applicability in paediatrics. In part I, reference intervals for different periods of childhood were determined. Except for the neonatal period there was no age-dependence so that children aged one week to 16 years have been summarized in one group. The wide variations we found in preterm children can be explained by different erythropoietic stimuli as the result of anaemia in infants with very low birthweight. No significant differences could be found between the sexes, not even at the onset of puberty. When using the reticulocyte maturity pattern analysis in clinical practice, the data give a helpful indication of the efficiency of the erythropoietic system.

Reticulocyte maturity as an indicator for estimating qualitative abnormality of erythropoiesis

AIMS

To determine the maturity of reticulocytes in patients with anaemia as a result of various haematological disorders including those with qualitative abnormalities such as ineffective erythropoiesis or dyserythropoiesis.

METHODS

The number of mature reticulocytes was measured with flow cytometry in venous blood samples from 122 patients with haematological disorders and 100 healthy controls. Reticulocytes were classified into three categories by the fluorescence intensity of auramin O staining: low fluorescence ratio (LFR), medium fluorescence ratio (MFR), and high fluorescence ratio (HFR). Immature reticulocytes were determined as the aggregate of MFR and HFR (%).

RESULTS

The mean (2SD) number of immature reticulocytes in 100 normal subjects was 9.0 (7.0)%. Significantly high mean values of immature reticulocytes with a normal or reduced reticulocyte count were shown in 90 patients with dyserythropoietic or ineffective erythropoietic conditions, such as acute myeloid leukaemia (AML) (n = 37), myelodysplastic syndrome (MDS) (n = 35), aplastic anaemia (AA) (n = 8), or megaloblastic anaemia (MA), (n = 6). Reticulocyte ratios returned to normal after successful treatment of patients with AML (n = 10) and MA (n = 3). However, high percentages of immature reticulocytes with increased reticulocyte counts were consistently observed in patients with enhanced erythropoiesis such as those with acquired autoimmune haemolytic anaemias (AIHA) (n = 4) or acute blood loss (ABL) (n = 4). Reticulocyte maturity was within the normal range in patients with reduced erythropoiesis such as occurs in chronic renal failure (CRF) (n = 11), or in iron deficiency anaemia (IDA) (n = 13).

CONCLUSIONS

The evaluation of reticulocyte maturity with total reticulocyte count seems to be clinically useful for estimating the qualitative impairment of erythropoiesis, and so could help differentiate haematological disorders.

Recombinant human insulin-like growth factor 1 (rh-IGF-1) stimulates erythropoiesis in adult, but not in newborn mice

The in vivo effect of recombinant human insulin-like growth factor (rh-IGF-1) upon erythropoiesis was studied in inbred BALB/C mice. Unweaned, rapidly growing 20 days old mice and adult female mice received subcutaneous rh-IGF-1 or control injections every 6 h for 48 h. The mice were killed either 12 or 48 h after the last injection, i.e. a study time of 60 and 96 h, respectively. Bone marrow erythroid colony forming units (CFU-E), reticulocytes, haematocrit, serum immunoreactive erythropoietin (siEPO) and body and organ weight were measured. An additional group of young mice were given iron prior to the rh-IGF-1 injections to ensure sufficient available iron. No differences in overall body or organ weights were observed. In the young mice erythropoiesis as measured by bone marrow CFU-E, reticulocytes and haematocrit did not differ between rh-IGF-1 group and controls. When iron alone was given, reticulocytes (P < 0.05) and haematocrit (P < 0.0001) increased significantly, but no further stimulation was seen when rh-IGF-1 injections were given in addition to iron. The adult female mice responded with significantly increased erythropoiesis as judged by increased reticulocyte counts following rh-IGF-1 injections (P < 0.001). No significant effect upon CFU-E and haematocrit was detected. The reticulocyte response was more pronounced at 96 than at 60 h after the first rh-IGF-1 injection. SiEPO was significantly (P < 0.01) lower in the adult 96 h rh-IGF-1 group than in the appropriate control group. In conclusion parenteral iron significantly increased haematocrit in unweaned mice. Short time rh-IGF-1 treatment did not stimulate erythropoiesis in these rapidly growing mice, whether or not iron supplementation had been given.(ABSTRACT TRUNCATED AT 250 WORDS)

Flow cytometric reticulocyte analysis and the reticulocyte maturity index

Reticulocyte analysis has evolved to one of the accepted and routinely practiced clinical applications of flow cytometry technology. Similar to CD4 measurements, FCM technology has contributed to documented improvements in reticulocyte counting precision over previous microscope-based techniques. The ability to FCM instruments to quantitate fluorescence intensity has been utilized to derive a parameter of reticulocyte maturity, which we have termed the reticulocyte maturity index. The FCM-derived RMI parameter offers an additional perspective to assess the erythropoietic response in anemic patients over reticulocyte counting alone and provides further insight into the differential diagnosis of anemia. Clinical utility of the RMI has been reported in monitoring expensive, new-technology therapies, such as bone marrow transplantation and erythropoietin therapy. FCM reticulocyte analysis is still not fully mature, but is in a state of continued evolution. Needs exist for (i) improved software for data analysis, (ii) newer automation techniques to improve interlaboratory correlations, and (iii) further validation and refinement of the reticulocyte maturity index parameter.

Reticulocyte count with maturation fractions in pancytopenic evaluation by a fully automated counter

Using a fully automated reticulocyte counter, the roles of the reticulocyte count with maturation in pancytopenia were evaluated. Different groups of pancytopenia including aplastic anemia, infiltrative marrow disorder, hypersplenism, and megaloblastic anemia were recruited. All patients had bone marrow examinations for morphological diagnosis and reticulocyte evaluation using an automated counter. The roles of these parameters were then analyzed statistically in the differential evaluation among these conditions. The following subjects were studied: 292 normal subjects, 67 cases of aplastic anemia, 69 cases of marrow infiltration by different malignancies, 35 cases of hypersplenism, and 13 cases of megaloblastic anemia. The results showed that the absolute reticulocyte counts were lowest in the groups of aplastic anemia and megaloblastic anemia and highest in hypersplenism. Both showed significant differences from the infiltrative groups. The maturation fractions were most immature in the group of marrow infiltration and are significantly different from the other groups. It was concluded that the highest absolute reticulocyte count (> 0.09 10(12)/L) obtained in pancytopenic patients suggests it to be a case of hypersplenism. The lowest counts (< 0.03 10(12)/L) with lowest immature fractions (< 10%) suggest the groups of aplastic or megaloblastic anemias. The highest immature fractions (> 30%) with a nearly normal reticulocyte count favor the group of marrow infiltration.

Proposal for standardization of flow cytometric reticulocyte maturity index (RMI) measurements

Flow cytometric (FCM) reticulocyte analysis is more accurate, sensitive, and reproducible relative to previously employed manual microscopic methods in clinical laboratory hematology. FCM reticulocyte analysis using RNA binding fluorochromes additionally allows for the quantification of fluorescence intensity or population distribution of the reticulocyte RNA content. Viewed from the perspective of erythroid maturation, quantification of the fluorescence intensity distribution provides a reticulocyte maturation index (RMI). We performed a systematic study of 18 different methods to express thiazole orange stained reticulocyte fluorescence intensity, compared to standard mean fluorescence intensity quantification, using 185 anemic and non-anemic human blood samples. The method best correlating with the mean fluorescence intensity RMI on 2 different FCM instruments (R2 = 0.93 and 0.86) was a ratio of the highly fluorescent reticulocytes, defined using a normal adult population, and the total number of reticulocytes (HFR%). In contrast to mean fluorescence intensity measurements, a HFR% RMI parameter can provide similar units of expression (0.01-1.00) with good correlation between different FCM instruments (R2 = 0.76). We conclude the HFR% method of RMI expression provides a superior means of interlaboratory standardization and clinical comprehension of this useful diagnostic parameter in clinical laboratory hematology.

Identification of CD71 (transferrin receptor) expressing erythrocytes by multiparameter-flow-cytometry (MP-FCM): correlation to the quantitation of reticulocytes as determined by conventional microscopy and by MP-FCM using a RNA-staining dye

Reticulocytes express the CD71-defined antigen, the transferrin receptor. This report describes how by means of dual-colour immunofluorescence using MP-FCM (multiparameter-flow-cytometry) CD71+ erythrocytes can be detected regularly in blood of healthy adults. Percentages of these CD71+ erythrocytes were compared to the percentages of reticulocytes as determined by conventional microscopy using brilliant cressyl blue, and to the percentages of erythrocytes with high RNA content, as detected by MP-FCM using a RNA-staining dye (thiazole-orange). Only about two-thirds of the percentages determined by the two latter methods were detected by MP-FCM using the CD71 expression for definition of reticulocytes. Studying clinical samples, however, including both specimens with very low and very high numbers of reticulocytes, almost identical percentages were determined by all the three methods described. Studying reticulocytes in vitro, a rapid decline of the expression of the transferrin receptor was observed on reticulocytes. Due to the differential expression of the transferrin receptor on reticulocytes, different subsets of reticulocytes could be identified. The dual-colour MP-FCM method described allows for the characterization and enumeration of immature erythrocytes, representing the major subset of reticulocytes as determined by conventional methods. Furthermore, it allows for subset dissection of reticulocytes.

Reticulocyte counting in thalassemic and other conditions with the R-1000 Sysmex analyzer

Precise reticulocyte counts are difficult to obtain by the manual method when their percentage in the blood is low or normal. In these instances, rapid reticulocyte counting by flow cytometry appears to offer more accuracy and precision. The purpose of this study was to establish reticulocyte counts in heterozygous beta-thalassemia for reference purposes and to evaluate the performance of the recently introduced apparatus R-1000 (Sysmex) in the very heterogeneous thalassemic and sickle-cell syndromes. We studied a total of 364 samples; 102 heterozygous beta-thalassemia carriers, 180 normal matched controls, 36 patients with thalassemia major or intermedia, and 46 patients with various sickle-cell syndromes. Reticulocyte counts (both as percentage and as total number) were higher in heterozygous beta-thalassemia than in normal controls (p less than 0.001) and showed an inverse correlation with the respective hemoglobin values (p less than 0.001). These results confirm the proposed slightly increased erythropoietic activity in heterozygous beta-thalassemia carriers. A drawback of the technique is that the reticulocyte-platelet discrimination error is signaled frequently in all conditions displaying a marked red cell heterogeneity, especially when these are associated with high reticulocyte numbers. This calls probably for readjustment of the corresponding algorithm. In addition, all these conditions show a significantly increased auramine-O mature red-cell nonspecific fluorescence.