Laboratory evaluation of the Sysmex SE-9500 automated haematology analyser.

The Sysmex SE-9c500 is a new, fully automated haematology analyser, providing a complete blood count (CBC), including a five-part differential count (DC), with flagging of morphological abnormalities. The SE-9500 was evaluated according to guidelines published by the International Committee for Standardisation in Haematology (ICSH). The results demonstrated minimal carryover (< 0.01%) and excellent linearity for WBC, RBC, HGB and platelet (PLT) (r > 0.995). Samples were stable with regard to CBC parameters after storage for up to 48 h at room temperature (RT) and 4 degrees C. Imprecision was generally acceptable for all CBC parameters (CV < 5%). Correlation between the SE-9500 and reference methods was excellent (r > 0.97) for all the major CBC parameters (WBC, RBC, HGB, PLT). There was minimal interference for WBC, RBC, HGB and PLT at high concentrations of bilirubin (BIL=224 micromol/l) or triglyceride (TG=7.78 mmol/l). SE-9500 reference values for CBC parameters are presented. Our results indicate that the SE-9500 is an excellent tool for routine haematological examination.     

Laboratory evaluation of the Sysmex SE‐9500 automated haematology analyser

The Sysmex SE‐9c500 is a new, fully automated haematology analyser, providing a complete blood count (CBC), including a five‐part differential count (DC), with flagging of morphological abnormalities. The SE‐9500 was evaluated according to guidelines published by the International Committee for Standardisation in Haematology (ICSH). The results demonstrated minimal carryover (< 0.01%) and excellent linearity for WBC, RBC, HGB and platelet (PLT) (r > 0.995). Samples were stable with regard to CBC parameters after storage for up to 48 h at room temperature (RT) and 4 °C. Imprecision was generally acceptable for all CBC parameters (CV < 5%). Correlation between the SE‐9500 and reference methods was excellent (r > 0.97) for all the major CBC parameters (WBC, RBC, HGB, PLT). There was minimal interference for WBC, RBC, HGB and PLT at high concentrations of bilirubin (BIL=224 μmol/l) or triglyceride (TG=7.78 mmol/l). SE‐9500 reference values for CBC parameters are presented. Our results indicate that the SE‐9500 is an excellent tool for routine haematological examination.     

冷凝集对血细胞分析多项参数检测结果的影响

目的 探讨红细胞冷凝集对血细胞分析各项检测参数的影响及处理方法.方法 选择福建省肿瘤医院2017年12月至2020年2月有红细胞冷凝集的全血标本73份.应用Sysmex XN-9000全自动血细胞分析仪对标本进行检测,比较37℃水浴前后红细胞(RBC)、血细胞比容(HCT)、平均红细胞体积(MCV)、平均红细胞血红蛋白...     

Initial performance evaluation of the UniCel® DxH 800 Coulter® cellular analysis system

The Beckman Coulter UniCel^® DxH 800 is a hematology analyzer incorporating new electronic and mechanical design with advanced algorithm technology to perform CBC, white blood cell (WBC) differential, nucleated red blood cell (NRBC), and reticulocyte analysis. Evaluation of this instrument was performed in our 800‐bed tertiary care hospital and specifically centered upon the correlation of WBC, NRBC, and platelet (PLT) enumeration when compared to a predicate analyzer, the Coulter^® LH 780, and flow cytometry (FCM) reference methods. Of particular interest were those samples with morphologically confirmed interference and extreme leukocytosis (evaluated with respect to red blood cell parameter correction). The sample set (n = 272) consisted of morphologically normal and hematologically abnormal patients. Correlation of the WBC, PLT, and NRBC showed r² values of 0.994, 0.985, and 0.910 for the DxH 800 vs. FCM, respectively. The presence of interfering particles did not affect the accuracy of the DxH 800 with respect to WBC counts. The DxH 800 showed accurate PLT and NRBC counts in the clinically significant low range when compared to FCM. Compared to the LH 780, flagging rates were significantly reduced (NRBC flag), or equivalent (WBC, PLT flag) on the DxH 800. The DxH 800 demonstrated higher sensitivity and specificity for PLTs and NRBCs and achieved a lower NRBC false negative rate compared to the LH 780. The UniCel^® DxH 800 represents a significant improvement to previous impedance analyzers in accurately detecting the presence of NRBCs at counts >1/100 WBC. Furthermore, it provides accurate PLT and WBC counts in the presence of interference and improved NRBC flagging efficiency when compared to the LH 780. Correction of red blood cell parameters is appropriate and accurate in cases of extreme leukocytosis.     

Performance evaluation of Abbott CELL‐DYN Ruby for routine use

CELL‐DYN^® Ruby? is a new automated hematology analyzer suitable for routine use in small laboratories and as a back‐up or emergency analyzer in medium‐ to high‐volume laboratories. The analyzer was evaluated by comparing the results from the CELL‐DYN^® Ruby? with the results obtained from CELL‐DYN^® Sapphire?. Precision, linearity, and carryover between patient samples were also assessed. Precision was good at all levels for the routine cell blood count (CBC) parameters, CV% being ≤2.6, except for platelet count (PLT) at the low level with CV% of ≤6.9%. The CV% for reticulocyte percentage was highest at the low level (10.4). In a comparative study, the CELL‐DYN Ruby results showed a good correlation (R² ≥ 0.98) with CELL‐DYN Sapphire for the CBC parameters. For the absolute reticulocyte count, R² was 0.82. In the white blood cell (WBC) differentials, the between‐days precision was good for all parameters (CV%: ≤8.0), except basophil percentage and absolute basophil count (CV%: ≤31.8 and 31.3, respectively). Additionally, in the commercial control sample with the low WBC count (2.5 × 10⁹/l), the precisions in the WBC differentials were ≤16.9%. The cell types that occur in low numbers showed higher CVs, as expected. The methodological comparison of the WBC differential parameters of neutrophils, lymphocytes, and eosinophils showed excellent correlations (R² ≥ 0.97), and the correlation coefficient for absolute monocyte count and monocyte percentage were 0.91 and 0.87, respectively. For absolute basophil count and basophil percentage the correlations were weaker (R² = 0.46 and 0.34, respectively). Carryover was minimal for all the parameters studied. The linearities of WBC, red blood cell, PLTs, and hemoglobin were acceptable within the tested ranges. In conclusion, the results of the evaluation showed the performance of CELL‐DYN Ruby to be good.     

Evaluation of hematological values obtained with reference automated hematology analyzers of six manufacturers

We evaluated assays of the same fresh blood samples with six different types of reference automated hematology analyzers developed by the following manufacturers: Beckman Coulter, Sysmex, Bayer, Abbott, Nihon Kohden and Horiba. Fresh whole blood samples treated with dipotassium ethylenediaminetetraacetic acid (EDTA K2) were collected from three healthy adult volunteers. The complete blood counts (CBC) including red blood cell count (RBC), hemoglobin (Hgb), hematocrit (Hct), mean corpuscular volume (MCV), white blood cell count (WBC), platelet count (Plt), reticulocyte percentage (Ret) and leukocyte differential counts including % neutrophils (Neu), % lymphocytes (Lym) and % monocytes (Mon) were surveyed with a reference automated hematology analyzer from each manufacturer. The process from sampling to analysis was performed according to procedures in hospital clinical laboratories. RBC, Hgb, Hct and MCV exhibited allowable differences within 5% of mean value among all instruments. Large differences greater than 10% of mean value in WBC, Neu and Lym between Horiba and other manufacturers, and in Plt between Nihon Kohden and other manufacturers, were observed. Ret and Mon exhibited large differences over 10% of mean value among almost all of the instruments tested. This survey suggests that all parameters exhibiting differences greater than 10% of mean value among instruments should be improved for clinical use to ensure good external quality control in blood cell counting and leukocyte differential counting using automated instruments.     

Study on the accuracy of automated hematology analyzers in Shanghai

The objectives of this study were to research on the accuracy of automated hematology analyzers of various types from different manufacturers and to observe the deviation among these instruments. Fresh anticoagulated blood from healthy donors on 115 hematology analyzers in 114 different hospitals were determined. RESULTS: The maximum coefficients of variation (CVs. %) among instruments of three main manufacturers (Sysmex, Beckman Coulter and Abbott) of red blood cell count (RBC), hemoglobin (Hgb), hematocrit (Hct), white blood cell count (WBC) and platelet count (Plt) were 3.2%, 3.8%, 3.6%, 9.3% and 10.8%, respectively. The maximum deviations among these parameters of different instruments were 0.74%, 1.65%, 5.45%, 7.06% and 18.55%, respectively. By improving laboratory quality management, the results of hematology analyzer determination may be more reliable than manual methods. The difference among various manufacturers was very small about RBC, Hgb, Hct, WBC and Plt the results from all kinds of instruments will tend to be comparable.     

Haematological reference values in Spanish adolescents: the AVENA study

Objectives: To provide reference values for haematological indices in Spanish adolescents according to age and gender. Methods: A cross sectional study conducted in five Spanish cities was performed. Blood was drawn from a representative sample of 581 adolescents with age ranging from 13 to 17–18.5 yr. Age‐ and gender‐specific means, standard deviations and percentiles were determined for the following parameters: total red blood cell counts (RBC), haemoglobin concentration (Hb), haematocrit percentage (Hct), mean corpuscular volume (MCV), mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, red cell distribution width and total white blood cell (WBC) counts as well as counts and percentage of neutrophils, lymphocytes, monocytes, eosinophils and basophils; platelet count (PLT), mean platelet volume and plateletcrit percentage. Results: Younger male subjects presented lower RBC, Hb, Hct and MCV means that their older counterpart. By contrast these differences were not observed in female subjects. As expected, RBC, Hb and Hct mean values in males were found significantly higher than in girls for all studied age groups. No significant differences were observed in WBC by age and gender. PLT values gradually decreased with age, except for females aged 17–18.5 yr. Conclusion: The present study provides reference data on the distribution of haematological indices of Spanish adolescents. These data can be useful biomarkers of the nutritional status in adolescents.     

Significant differences between capillary and venous complete blood counts in the neonatal period

The normal capillary and venous hematologic values for neonates have not been defined clearly. It is well known that capillary blood has higher hemoglobin (Hb) and hematocrit (Hct) values than venous blood. In a recent study, we reported differences between capillary and venous complete blood counts (CBC) in healthy term neonates on day 1 of life. The aim of this study was to extend our previous investigation. Term neonates (n=141) were stratified into four groups by days of postnatal age: group 2 (day 7, n=38), group 3 (day 14, n=35), group 4 (day 21, n=32) and, group 5 (day 28, n=36). Data from our previous study were included in the statistical analysis as group 1 (day 1, n=95). A CBC and differential count were carried out on each capillary and venous sample drawn simultaneously. Within each group, the mean and standard deviation for each parameter in capillary and venous blood were calculated and then compared using the paired sample t-test. In all groups, the capillary blood samples had higher Hb, Hct, red blood cell (RBC), white blood cell (WBC), and lymphocyte counts. In each group, venous platelet counts were significantly higher than the corresponding capillary values. There was also a trend toward higher venous mean corpuscular volume, higher capillary polymorphonuclear leukocyte (PML) count and mean platelet volume in all groups. In both capillary and venous blood, Hb, Hct, RBC, MCV values and WBC, lymphocyte, PML counts decreased and platelet counts increased steadily during neonatal period. This study reveals that CBC parameters and differential counts may differ depending on the blood sampling used. The findings underline the importance of considering the sample source when using hematologic reference ranges for healthy or septic neonates. When interpreting results, the term 'peripheral blood' should be replaced with 'capillary blood' or 'venous blood' so that an accurate assessment can be made.     

血细胞自动分析仪检测疟疾患者血常规的诊断意义

目的探讨血细胞分析仪血常规指标与疟疾的关系,特别是血小板数量与疟疾的关系。方法用全自动血细胞分析仪对疟疾病人及正常对照、非疟疾发热病人进行血常规检查,对比分析血小板、红细胞、血红蛋白、白细胞及白细胞分类直方图,并用染色镜检查疟原虫。结果疟疾病人的血小板及其红细胞、血红蛋白、白细胞都呈显著性减少,血小板减少幅度最为显著,白细胞直方图呈正常双峰,也可在 35fl处见有抬高现象。结论发热病人,特别是高热病人,如经血细胞分析仪检查血常规发现有血小板减少时,白细胞计数不增高,且其直方图为正常双峰图形,应高度怀疑为疟原虫感染,可涂血片染色镜检疟原虫。     

Spurious counts and spurious results on haematology analysers: a review. Part II: white blood cells, red blood cells, haemoglobin, red cell indices and reticulocytes

Haematology analysers provide quick and accurate results in most situations. However, spurious results, related either to platelets (part I of this report) or to other parameters from the cell blood count (CBC) may be observed in several instances. Spuriously low white blood cell (WBC) counts may be observed because of agglutination in the presence of ethylenediamine tetra-acetic acid (EDTA). Cryoglobulins, lipids, insufficiently lysed red blood cells (RBC), erythroblasts and platelet aggregates are common situations increasing WBC counts. In most of these instances flagging and/or an abnormal WBC differential scattergram will alert the operator. Several situations lead to abnormal haemoglobin measurement or to abnormal RBC count, including lipids, agglutinins, cryoglobulins and elevated WBC counts. Mean (red) cell volume (MCV) may be also subject to spurious determination, because of agglutinins, excess of glucose or salts and technological considerations. In turn, abnormality related to one measured parameter will lead to abnormal calculated RBC indices: mean cell haemoglobin content (MCHC) is certainly the most important RBC indices to consider, as it is as important as flags generated by the haematology analysers (HA) in alerting the user to a spurious result. In many circumstances, several of the measured parameters from CBC may be altered, and the discovery of a spurious change on one parameter frequently means that the validity of other parameters should be considered. Sensitive flags now allow the identification of several spurious counts, but only the most sophisticated HA have optimal flagging and more simple HA, especially those without a WBC differential scattergram, do not possess the same sensitivity for detecting anomalous results. Reticulocytes are integrated now into the CBC in many HA, and several situations may lead to abnormal counts.     

Aging stability of complete blood count and white blood cell differential parameters analyzed by Abbott CELL-DYN Sapphire hematology analyzer

This study presents the results of an aging stability study of complete blood count (CBC) and leukocyte differential parameters using the Abbott CELL-DYN Sapphire hematology analyzer. Stability studies showed no substantial change in CBC parameters up to 24-48 h at +23 +/- 2 degrees C (room temperature), except for optical platelet count (PLTo). For specimens aged over 24, the value of impedance platelet count yielded more reliable results than the routine PLTo. White blood cell (WBC) differential parameters, except eosinophils, were stable for up to 48 h at +23 +/- 2 degrees C. CBC parameters were stable for 72 h, except mean platelet volume, which slightly increased between 48 and 72 h, at +4 degrees C. WBC differentials were stable 48-72 h, with a slight decrease observed in absolute neutrophils and lymphocytes at +4 degrees C.     

Rapid testing of red blood cells,white blood cells and platelets in intensive care patients using the HemoScreen™ point-of-care analyzer

Acute major bleeding is a condition that can be encountered in critically ill patients and may require rapid transfusions. To evaluate the need for packed red blood cells (RBCs) and platelets (PLTs), it is important to have rapid test results for RBC/hemoglobin and PLTs. Recently, PixCell Medical (Yokneam Ilit, Israel) introduced the HemoScreen?, an automated hematology analyzer. It is a point-of-care device that uses single sample cuvettes and image analysis of RBCs, PLTs and white blood cells (WBCs), performing a five-part differential count. The HemoScreen? is the first portable differential count instrument that uses image analysis. We compared the RBC, PLT, and WBC test results of the HemoScreen? with the Sysmex XN device. In the study we analyzed 104 samples from the cardiothoracic, neuro and general intensive care units.

The HemoScreen? technique showed good precision, with total coefficient of variation of 1–2% for RBCs and 3–5% for PLTs. Deming correlations between the HemoScreen and the Sysmex XN instrument analyzer: (WBC_HemoScreen? = 1.061* WBC_Sysmex - 0.644; r = 0.995), RBC (RBC_HemoScreen? = 0.998* RBC_Sysmex + 0.049; r = 0.993) for WBC and (Platelets_HemoScreen? = 1.087* Platelets_Sysmex – 14.80; r = 0.994) for PLT. The HemoScreen? device provided rapid and accurate test results to evaluate the need for RBC and PLT transfusion. This new technology is promising given that it allows the analysis of WBCs, RBCs, and PLTs further out in the healthcare organization compared with laboratory infrastructure based on traditional cell counters.     

Venous stasis and routine hematologic testing

Prolonged venous stasis, as generated by a long tourniquet placement, produces spurious variations in several measurable analytes. To verify to what extent venous stasis influences routine hematologic testing, we assessed routine hematologic parameters, including hemoglobin, hematocrit, red blood cell count (RBC), main cell hemoglobin (MHC), main cell volume (MCV), platelet count (PLT), main platelet volume (MPV), white blood cell count (WBC) and WBC differential on the Advia 120 automated hematology analyzer in 30 healthy volunteers, either without venous stasis (no stasis) or after application of a 60 mmHg standardized external pressure by a sphygmomanometer, for 1 (1-min stasis) and 3 min (3-min stasis). Although the overall correlation between measures was globally acceptable, the mean values for paired samples were significantly different in all parameters tested, except MCV, MHC, PLT, MPV, eosinophils, basophils and large unstained cells after 1-min stasis and all parameters except MCV, MHC, MPV and basophils after 3-min venous stasis. As expected RBC, hemoglobin and hematocrit displayed a significant trend towards increase, whereas WBC and the WBC subpopulations were decreased. Difference between measurements by Bland and Altman plots exceeded the current analytical quality specifications for desirable bias for WBC, RBC, hemoglobin, hematocrit, lymphocytes and monocytes in samples collected after either 1- and 3-min stasis. These results provide clear evidence that venous stasis during venipuncture might produce spurious and clinically meaningful biases in the measurement of several hematologic parameters, prompting further considerations on the usefulness of adopting appropriate preventive measures for minimizing such influences.     

The soluble interleukin-2 receptor, peripheral blood, and reticulocyte fractions in acute pancreatitis

Summary Conclusion In acute pancreatitis (AP), the peripheral blood analysis, including reticulocytes (RC) and RC fractions, and its relationship to the changes of the levels of the soluble interleukin 2 receptor (sIL-2R) can provide useful information about the involvement of the immunoinflammatory system in AP and can indicate the severity of the disease. Background In the disease clinical assessment, we correlated the sIL-2R serum levels to the peripheral blood components (including RC and RC fractions) to serum albumin and C-reactive protein (CPR) during AP. Methods In 21 patients with AP, sIL-2R, the total and differential white blood cell (WBC) counts, red blood cell (RBC) counts, RC, RC fractions, hemoglobin (Hb), hematocrit (Ht), platelets (PLT), albumin, and CRP were evaluated from the onset to the sixth day of illness. Results sIL-2R increased in all the patients. The increase was directly related to eosinophils, monocytes, and to middle-aged (MFR) RC, and inversely related to neutrophils and the old (LFR) RC. MFR-RC were directly related to the total WBC count, esoninophils, and basophils, and inversely related to Hb and albumin. LFR-RC behaved in the opposite manner. CRP increased in 16 patients; this rise was directly related to WBC, RC, and MFR-RC, and inversely related to Hb, LFR-RC, and albumin. sIL-2R and CRP values were not statistically interrelated, but when the CRP levels were higher, the increase in sIL-2R was greater and more sustained.     

Comprehensive pediatric reference intervals for 79 hematology markers in the CALIPER cohort of healthy children and adolescents using the Mindray BC-6800Plus system

Background

Hematological parameters vary significantly throughout growth and development due to physiological processes such as fetal-to-adult erythropoiesis and puberty. Pediatric age- and sex-specific reference intervals (RIs) are thus essential for appropriate clinical decision-making. The current study aimed to establish RIs for both common and novel hematology parameters on the Mindray BC-6800Plus system.

Methods

Six hundred and eighty-seven healthy children and adolescents (30 days to 18 years) were enrolled. Participants were recruited as part of the Canadian Laboratory Initiative on Pediatric Reference Intervals Program upon informed consent or identified from apparently healthy outpatient clinics. Whole blood was collected and assayed for 79 hematology parameters on the BC-6800Plus system (Mindray). Age- and sex-specific RIs were established as per Clinical and Laboratory Standards Institute EP28-A3c guidelines.

Results

Dynamic reference value distributions were observed for several hematology parameters, including erythrocytes, leukocytes, platelets, reticulocytes, and research-use-only markers. Age partitioning was required for 52 parameters, demonstrating changes in infancy and puberty. Sex partitioning was required for 11 erythrocyte parameters (i.e., red blood cell (RBC), hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin concentration, RBC distribution width coefficient of variation, hemoglobin distribution width, macrocyte count, macrocyte percentage, RBC (optical), and reticulocyte production index). Few parameters had undetectable levels in our healthy cohort (i.e., nucleated RBC count and immature granulocyte count).

Conclusions

The current study completed hematological profiling for 79 parameters on the BC-6800Plus system in a healthy cohort of Canadian children and adolescents. These data emphasize the complex biological patterns of hematology parameters in childhood, particularly at the onset of puberty, and support the need for age- and sex-specific RIs for clinical interpretation.     

Chronic myelomonocytic leukemia with good response to low-dose etoposide]

58-year-old man was admitted with cervical tumor and leukocytosis. Physical examination indicated splenomegaly and cervical abscess. Laboratory data showed WBC 55,000/microliters, Hb 7.9g/dl, and PLT 4.5 x 10(4)/microliters. After cure of the abscess, WBC counts were still high with 1,500-2,000/microliters monocytes, and anemia and thrombocytopenia persisted. Bone marrow aspiration showed myeloid hyperplasia and trilineage myelodysplasia. The Ph1 chromosome could not be detected. The case was diagnosed as chronic myelomonocytic leukemia and treated with oral etoposide (25mg/day). After 2 weeks, the dose was increased to 50mg, and then modified according to the blood counts. WBC counts are presently being maintained between 7,000 and 12,000/microliters, and RBC and PLT counts have gradually become normal. Splenomegaly almost disappeared and dysplastic change in bone marrow improved somewhat. At nine months following the start of chemotherapy with etoposide, remission is maintained by treatment with 25mg of etoposide on alternate days. This case suggests that low-dose etoposide is useful for treating CMMoL.     

First clinical evaluation of the CELL-DYN® 3200 haematology analyser

A prototype of the CELL-DYN 3200® haematology analyser was evaluated in a tertiary care hospital laboratory. Precision, effects of sample ageing, linearity, carry-over, and com-parability of cellular blood counts and five-part leucocyte differentiation were determined in accordance with the ICSH guidelines for the evaluation of blood cell analysers; the results were satisfactory for all parameters tested: haemoglobin concentration, RBC, MCV, WBC, platelet count, and counts of neutrophils, lymphocytes, monocytes, and eosinophils. Two-hundred and forty-seven routine blood samples were used for the comparability studies. The cellular blood count results from the CELL-DYN 3200® and the Bayer Diagnostic H-1 systems corresponded closely (correlation coefficient r > 0.96 for all parameters). For 201 samples without an instrument-generated suspect flag the same was true with regard to the dif-ferential parameters, although somewhat lower correlation was observed for monocyte counts (r = 0.88). Comparisons to 400-cell microscopic differentials gave similar results (r > 0.93 for neutrophil, lymphocyte and eosinophil counts). Our results suggest that the CELL-DYN 3200® analyser will serve the needs for automated blood cell counting and differential leucocyte counting in a tertiary care hospital laboratory.     

光学法计数在低值血小板检测中的研究应用

目的：评价光学法计数在低值血小板检测中的研究应用。方法：200例低值血小板患者血标本,在血液分析仪上分别进行电阻抗法和光学法血小板计数,同时进行镜检法计数。结果：以镜检法为参考方法,光学法的相关系数为0．994。电阻抗法的相关系数0．921。在小红细胞组、红细胞碎片组和大血小板组,电阻抗法和镜检法计数结果差异有统计学意义（P〈0．05）,光学法和镜检法计数结果差异无统计学意义（P〉0．05）。结论：光学法计数可以满足低值血小板检测准确性的要求,值得临床实验室推广应用。     

Postnatal ontogeny of erythropoietin and hematology in free-ranging Steller sea lions (Eumetopias jubatus)

The hormone erythropoietin (EPO) is responsible for the increased production of red blood cells (RBC) in response to tissue hypoxia. While the role of EPO in hematological development has been established in humans and terrestrial mammals, this relationship has never been examined in marine mammals that rely heavily on stored oxygen to maintain aerobic metabolism while diving. Since blood is the major oxygen storage site in marine mammals, it was hypothesized that EPO may have a significant influence on the development of hematology parameters associated with the expansion of blood oxygen stores during development. To explore this hypothesis, serum EPO concentrations were determined by radioimmunoassay in 235 free-ranging Steller sea lions (Eumetopias jubatus), throughout their Alaskan range. Hematocrit (Hct), hemoglobin (Hb), and red blood cell (RBC) counts were also measured, and mean corpuscular hemoglobin content (MCHC), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCV) values determined. Erythropoietin and most hematological parameters varied with age. Hematocrit, Hb, RBC, and MCHC decreased after birth, reached their lowest values at two to three months of age, and then increased to values similar to those of adults by five months of age. Since changes in Hct and Hb account for the majority of the changes in blood oxygen stores and EPO was negatively correlated with both, it appears that EPO may play an important role in blood development of Steller sea lions, similar to previous studies on terrestrial mammals.