Percentage of hypochromic erythrocytes and reticulocyte hemoglobin equivalent predictors of response to intravenous iron in hemodialysis patients

Recommendations for diagnosis, treatment, and prevention of iron deficiency and iron deficiency anemia

Iron is an essential nutrient and a constituent of ferroproteins and enzymes crucial for human life. Generally, nonmenstruating individuals preserve iron very efficiently, losing less than 0.1% of their body iron content each day, an amount that is replaced through dietary iron absorption. Most of the iron is in the hemoglobin (Hb) of red blood cells (RBCs); thus, blood loss is the most common cause of acute iron depletion and anemia worldwide, and reduced hemoglobin synthesis and anemia are the most common consequences of low plasma iron concentrations. The term iron deficiency (ID) refers to the reduction of total body iron stores due to impaired nutrition, reduced absorption secondary to gastrointestinal conditions, increased blood loss, and increased needs as in pregnancy. Iron deficiency anemia (IDA) is defined as low Hb or hematocrit associated with microcytic and hypochromic erythrocytes and low RBC count due to iron deficiency. IDA most commonly affects women of reproductive age, the developing fetus, children, patients with chronic and inflammatory diseases, and the elderly. IDA is the most frequent hematological disorder in children, with an incidence in industrialized countries of 20.1% between 0 and 4 years of age and 5.9% between 5 and 14 years (39% and 48.1% in developing countries). The diagnosis, management, and treatment of patients with ID and IDA change depending on age and gender and during pregnancy. We herein summarize what is known about the diagnosis, treatment, and prevention of ID and IDA and formulate a specific set of recommendations on this topic.

Reference intervals for reticulocyte indices, immature reticulocyte fraction, and the percentage of hypochromic red blood cells in adult large breed dogs using the ADVIA 2120 hematology analyzer

Reticulocyte indices are used to characterize anemia, including the identification of regeneration. In people, the immature reticulocyte fraction (IRF), percentage of hypochromic red blood cells (%HYPO-RBC), and other reticulocyte indices have been used as earlier indicators of erythropoiesis and as valuable monitoring tools in the assessment of various therapies. The reference intervals (RI) of the IRF and %HYPO-RBC have not been reported in dogs. The objective of this study was to establish RIs for novel variables (IRF, %HYPO-RBC, and CH-delta) and assess RIs for more commonly reported reticulocyte indices in healthy dogs. RIs were calculated from blood results retrospectively collected from 106 client-owned healthy dogs at the time of induction into a blood donor program using the ADVIA 2120 hematology analyzer (Siemens Healthcare Diagnostics). For the calculation of RIs, appropriate tests were applied for outlier detection and normality assessment. For variables normally distributed, RIs and their respective 90% confidence intervals (CIs) were calculated using parametric methods, while for variables not normally distributed, robust methods were used and bootstrapping for calculating the 90% CIs. The following RIs were established: reticulocyte hemoglobin content (CHr) 24.5-28 pg, mean reticulocyte volume (MCVr) 85.9-99.3 fL, mean corpuscular hemoglobin concentration of reticulocytes (CHCMr) 271.0-306.3 g/L, IRF 10.4%-43.5%, CH-delta 0.5-4.3 pg, and percentage of hypochromic red blood cells (%HYPO-RBC) 0.10%-0.80%. The results of this study provide RIs for novel reticulocyte variables. Further studies are required to determine the clinical utility of IRF, %HYPO-RBC, and CH delta as early indicators of erythropoietic activity in canine patients.

Neonatal Reference Intervals for the Complete Blood Count Parameters MicroR and HYPO-He: Sensitivity Beyond the Red Cell Indices for Identifying Microcytic and Hypochromic Disorders

OBJECTIVE

To create neonatal reference intervals for the MicroR and HYPO-He complete blood count (CBC) parameters and to test whether these parameters are sensitive early markers of disease at early stages of microcytic/hypochromic disorders while the CBC indices are still normal.

STUDY DESIGN

We retrospectively collected the CBC parameters MicroR and HYPO-He, along with the standard CBC parameters, from infants aged 0-90 days at Intermountain Healthcare hospitals using Sysmex hematology analyzers. We created reference intervals for these parameters by excluding values from neonates with proven microcytic disorders (ie, iron deficiency or alpha thalassemia) from the dataset.

RESULT

From >11 000 CBCs analyzed, we created reference intervals for MicroR and HYPO-He in neonates aged 0-90 days. The upper intervals are considerably higher in neonates than in adults, validating increased anisocytosis and polychromasia among neonates. Overall, 52% of neonates with iron deficiency (defined by reticulocyte hemoglobin equivalent <25 pg) had a MicroR >90% upper interval (relative risk, 4.14; 95% CI, 3.80-4.53; P < .001), and 68% had an HYPO-He >90% upper interval (relative risk, 6.64; 95% CI, 6.03-7.32; P < .001). These 2 new parameters were more sensitive than the red blood cell (RBC) indices (P < .001) in identifying 24 neonates with iron deficiency at birth.

CONCLUSIONS

We created neonatal reference intervals for MicroR and HYPO-He. Although Sysmex currently designates these as research use only in the US, they can be measured as part of a neonate's CBC with no additional phlebotomy volume or run time and can identify microcytic and hypochromic disorders even when the RBC indices are normal.

Prognostic impact of hypochromic erythrocytes in patients with pulmonary arterial hypertension

Background

Iron deficiency affects up to 50% of patients with pulmonary arterial hypertension (PAH) but iron markers such as ferritin and serum iron are confounded by several non-disease related factors like acute inflammation and diet. The aim of this study was to identify a new marker for iron deficiency and clinical outcome in PAH patients.

Methods

In this single-center, retrospective study we assessed indicators of iron status and clinical parameters specifying the time to clinical worsening (TTCW) and survival in PAH patients at time of initial diagnosis and at 1-year follow-up using univariable and multivariable analysis.

Results

In total, 150 patients were included with an invasively confirmed PAH and complete data on iron metabolism. The proportion of hypochromic erythrocytes > 2% at initial diagnosis was identified as an independent predictor for a shorter TTCW (p = 0.0001) and worse survival (p = 0.002) at initial diagnosis as well as worse survival (p = 0.016) at 1-year follow-up. Only a subset of these patients (64%) suffered from iron deficiency. Low ferritin or low serum iron neither correlated with TTCW nor survival. Severe hemoglobin deficiency at baseline was significantly associated with a shorter TTCW (p = 0.001).

Conclusions

The presence of hypochromic erythrocytes > 2% was a strong and independent predictor of mortality and shorter TTCW in this cohort of PAH patients. Thus, it can serve as a valuable indicator of iron homeostasis and prognosis even in patients without iron deficiency or anemia. Further studies are needed to confirm the results and to investigate therapeutic implications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01884-9.

Using Reticulocyte Hemoglobin Equivalent as a Marker for Iron Deficiency and Responsiveness to Iron Therapy

OBJECTIVE

To assess the accuracy of a simplified approach for the diagnosis of iron deficiency anemia (IDA) based on the complete blood cell count (CBC) and reticulocyte analysis.

PATIENTS AND METHODS

Five hundred fifty-six consecutive, nonselected patients referred for diagnosis and/or treatment of anemia were included in this diagnostic study to compare the performance of reticulocyte hemoglobin equivalent (RET-He) versus traditional biochemical markers for diagnosis and treatment of IDA. Complete blood count, serum ferritin, iron, and transferrin saturation were performed as clinically indicated. Reticulocyte hemoglobin equivalent was measured with a Sysmex XN-450 analyzer on the residual CBC sample. The study period was from September 20, 2017, through and including November 15, 2018.

RESULTS

Patients (N=556) were studied at baseline, of whom 150 were subsequently treated with intravenous iron. Receiver operating characteristic analysis yielded an RET-He cut-off of 30.7 pg to identify IDA (area under curve, 0.733; 95% CI, 0.692 to 0.775), with 68.2% sensitivity and 69.7% specificity. Patients (n=240) were seen at follow-up, with 57 treated and 183 not treated with intravenous iron. Responsiveness was defined as a hemoglobin increase of ≥1.0 g: a combination of RET-He <28.5 pg and hemoglobin value <10.3 g/dL had 84% sensitivity and 78% specificity as response predictor (area under the curve, 0.749; 95% CI, 0.622 to 0.875).

CONCLUSION

Data from CBC and RET-He can identify patients with IDA, determine need for and responsiveness to intravenous iron, and reduce time for therapeutic decisions. Limitations of this study are uncontrolled design, its single-site and retrospective nature, and that it requires prospective validation.

Iron deficiency

Iron deficiency is one of the leading contributors to the global burden of disease, and particularly affects children, premenopausal women, and people in low-income and middle-income countries. Anaemia is one of many consequences of iron deficiency, and clinical and functional impairments can occur in the absence of anaemia. Iron deprivation from erythroblasts and other tissues occurs when total body stores of iron are low or when inflammation causes withholding of iron from the plasma, particularly through the action of hepcidin, the main regulator of systemic iron homoeostasis. Oral iron therapy is the first line of treatment in most cases. Hepcidin upregulation by oral iron supplementation limits the absorption efficiency of high-dose oral iron supplementation, and of oral iron during inflammation. Modern parenteral iron formulations have substantially altered iron treatment and enable rapid, safe total-dose iron replacement. An underlying cause should be sought in all patients presenting with iron deficiency: screening for coeliac disease should be considered routinely, and endoscopic investigation to exclude bleeding gastrointestinal lesions is warranted in men and postmenopausal women presenting with iron deficiency anaemia. Iron supplementation programmes in low-income countries comprise part of the solution to meeting WHO Global Nutrition Targets.

Red Blood Cells and Platelets Conventional and Research Parameters: Stability Remarks Before Their Interpretation

OBJECTIVES

To analyze the stability of red blood cells, platelets, and reticulocytes of the research parameters, in combination with the respective conventional parameters, for each analyte; and to quantify the morphological changes in these analytes, to propose a correction factor for each.

METHODS

Ethylenediaminetetraacetic acid (EDTA) blood specimens from patients were reanalyzed in 2-hour intervals and then, the mean percentage (X¯t%) changes were calculated. To evaluate the stability of the analyzed material, we used different criteria according to within-run and between-batch analytical variation, as well as intraindividual biological variation. Next, the mean deviation percentage of the parameters that undergo time-dependent significant changes was calculated, to obtain a correction factor.

RESULTS

Several conventional and research parameters showed significant alterations in the stability at an early time after arrival at the laboratory.

CONCLUSION

Cell variations over time can be quantified and corrected by applying a multiplying factor to the signal obtained in the analyzer.

Preliminary assessment of the new Sysmex XN parameter Iron-Def for identifying iron deficiency

BACKGROUND

Although the clinical assessment of iron status is usually based on iron stores, a rapid and accurate diagnosis of iron deficiency is challenging since ferritin is often unavailable as an urgent test and its value is frequently increased in acute phase conditions. This study was therefore aimed at evaluating the diagnostic performance of the new Sysmex XN "Iron Deficiency?" (Iron-Def) parameter for identifying patients with iron deficiency.

MATERIALS AND METHODS

The study population consisted of 688 consecutive patients (median age: 71 years; 341 women and 347 men), referred for routine diagnostics to the Laboratory of Clinical Pathology of Lecco Hospital, Italy. A complete clinical chemistry profile and haematological testing were performed for identifying iron deficiency anaemia.

RESULTS

A significant negative correlation was found between Sysmex XN Iron-Def and ferritin, serum iron, mean cell haemoglobin concentration, mean cell haemoglobin, mean corpuscular volume and age, while a positive correlation was noted with transferrin, percentage of microcytic red cell, red blood cell count and red blood cell distribution width. The diagnostic accuracy of Iron-Def for identifying patients with a percentage of saturation of transferrin <15% (n=104) was 84%, with a sensitivity of 0.952 and specificity of 0.538. A sub-analysis of 71 patients with ferritin <20 ng/dL yielded an even better diagnostic performance (86%, with a sensitivity of 0.935 and specificity of 0.620).

DISCUSSION

Although additional confirmatory investigations would be needed, the preliminary findings of our study attest that Iron-Def may be an easy, inexpensive, rapid and reliable parameter for screening iron deficiency anaemia.

Diagnosis of iron deficiency in hemodialysis patients: Usefulness of measuring reticulocyte hemoglobin equivalent

The evaluation of iron status in dialysis patients provides information essential to the planning of adequate recombinant human erythropoietin treatment. To diagnose iron deficiency in patients undergoing hemodialysis (HD), reticulocyte hemoglobin content and percentage of hypochromic red cells are incorporated into the European best practice guidelines on anemia management in chronic kidney disease (CKD), the mean reticulocyte hemoglobin content (Ret-HE) was proposed as alternatives to standard biochemical tests. Reticulocyte hemoglobin content and percentage of hypochromic red cells are incorporated into the European best practice guidelines on anemia management in CKD. Our aim was to assess the value of Ret-HE parameter, in terms of the sensitivity and specificity for detecting iron deficiency, in HD patients. We studied 50 patients undergoing HD three times weekly , to clarify the accuracy of Ret-HE in diagnosing iron deficiency in dialysis patients, we initially compared Ret-HE with such iron parameters as serum ferritin levels, transferrin saturation, and hypochromic red blood cell (Hypo%) which has been established as indicators of functional iron deficiency. Ret-HE mean value in anemic patients was (25.84 ± 4.23 pg) and had good correlation (P <0.001) between Ret-HE, serum iron, ferritin, transferrin, and transferin saturation in dialysis patients. Receiver operating characteristic curve analysis revealed, values of the area was 0.887, and at a cutoff value of 27.0 pg, a sensitivity of 90.4% and a specificity of 80.8% were achieved. The newly proposed Ret-HE can provide clinicians with information equivalent to iron deficiency anemia markers. Ret-HE is a new parameter that is easily measurable is suggested as reliable parameters for the study of erythropoiesis status in HD patients.

Percentage of hypochromic red cells as a potential screening test to evaluate iron status in blood donors

INTRODUCTION

Haemoglobin (Hb) levels are used to assess eligibility for blood donation but are not correlated with iron status. The percentage of hypochromic red cells (%Hypo-He) has been suggested as a useful screening parameter for iron deficiency. The aim of this study was to determine the cut-off level and accuracy of %Hypo-He screening among blood donors.

MATERIALS AND METHODS

A total of 170 blood donors were recruited into the study. Blood donors were classified into three groups: normal, latent iron deficiency and iron deficiency anaemia based on their Hb, serum ferritin and transferrin saturation (TSAT) levels. The diagnostic performance of %Hypo-He was evaluated with a validation group comprising 160 blood donors.

RESULTS

Receiver operating characteristic (ROC) curve analysis showed that %Hypo-He is an excellent parameter for detecting iron deficiency, with an area under the curve (AUC) of 0.906, a confidence interval (CI) of 0.854-0.957 at a cut-off of 0.6%, and 74.51% sensitivity and 88.24% specificity. A moderate negative correlation between %Hypo-He and TSAT (ρ = -0.576 [P < 0.001]) and a strong negative correlation between %Hypo-He and serum ferritin (ρ = -0.703 [P < 0.001]) were found. A cut-off value of 0.6% was applied to the validation group and showed 82.9% sensitivity and 96% specificity.

CONCLUSION

%Hypo-He with a cut-off value of 0.6% is a potential parameter with high sensitivity and specificity for evaluating iron status among blood donors. This parameter is suitable for screening because its measurement has a faster turnaround time than biochemical markers.

Reticulocyte hemoglobin equivalent in a thalassemia-prevalent area

BACKGROUND

Reticulocyte hemoglobin equivalent (Ret-He), a direct measure of the hemoglobin (Hb) in the young red blood cells, has been reported to be useful in the diagnosis of iron deficiency anemia (IDA) but may have some limitations in thalassemia trait. This study evaluated the differences in Ret-He in school-aged children, and assessed the diagnostic value of Ret-He in identifying IDA in a thalassemia-prevalent area.

METHODS

Blood samples underwent complete blood count analysis, including Ret-He, ferritin, serum iron and total iron binding capacity. Blood samples also underwent Hb typing and a molecular study for α-thalassemia. Receiver operating characteristic analysis was performed to determine the predictive capacity of Ret-He in the diagnosis of IDA. ID was defined as serum ferritin <30 ng/mL and/or transferrin saturation (TSAT) <16%; IDA was defined as serum ferritin <12 ng/mL and/or TSAT <16% with low Hb for age. Normal healthy children (normal controls: NC) had normal iron study, without the thalassemia trait.

RESULTS

Ninety-eight children with a mean age of 12.9 ± 0.6 years were included. Ret-He in the thalassemia trait group (26.7 ± 2.4 pg), ID group (29.0 ± 2.9 pg), IDA group (25.4 ± 2.7 pg), ID + thalassemia trait group (26.6 ± 2.8 pg), and the IDA + thalassemia trait group (24.6 ± 2.3 pg) was significantly lower than in the NC group (30.8 ± 1.7 pg; P < 0.001, 0.01, 0.006, 0.002 and <0.001, respectively). Ret-He had an area under the curve of 0.904 in diagnostic ability for IDA, while a cut-off ≤27 pg had a sensitivity of 91.7% and a specificity of 81%.

CONCLUSION

Ret-He was lowest in subjects with IDA + thalassemia trait. A Ret-He cut-off ≤27 pg was suggestive of IDA in the present study.

Measurement of iron status in chronic kidney disease

Anemia is a common complication of chronic kidney disease (CKD) in children, and dysregulation of iron homeostasis plays a central role in its pathogenesis. Optimizing iron status is a prerequisite for effective treatment of anemia. Insufficient iron can lead to inappropriate escalation of the erythropoiesis-stimulating agent (ESA) dose, which is associated with adverse outcomes. Excess iron supplementation also has negative sequelae including free radical tissue damage and increased risk of systemic infection. Notwithstanding the importance of optimizing bioavailable iron for erythropoiesis for children with advanced CKD, achieving this remains challenging for pediatric nephrologists due to the historical lack of practical and robust measures of iron status. In recent years, novel techniques have come to the fore to facilitate accurate and practical assessment of iron balance. These measures are the focus of this review, with emphasis on their relevance to the pediatric CKD population.

Markers of iron status in chronic kidney disease

Anemia is one of the main comorbidities related to chronic kidney disease (CKD). Until the advent of erythropoiesis stimulating agents (ESA), endogenous erythropoietin deficiency has been thought to be the main culprit of anemia in CKD patients. The use of ESAs has shed new light on the physiology of CKD anemia, where iron homeostasis plays an increasingly important role. Disorders of iron homeostasis occurring in CKD turn the anemia management in those patients into a complex multifactorial therapeutic task, where ESA and Iron dose must be properly balanced to achieve the desired outcome without exposing the patients to the risk of serious adverse events. This review covers diagnostic markers traditionally used for quantifying iron status in CKD patients, such as serum ferritin and transferrin saturation, new ones, such as reticulocyte hemoglobin content and percent hypochromic red cells (HRC), as well as experimental ones, such as hepcidin and soluble transferrin receptor (sTfR). Each marker is presented in terms of their diagnostic performance, followed by biological and analytical variability data. Advantages and disadvantages of each marker are briefly discussed. Although serum ferritin and transferrin saturation are easily available, they exhibit large biological variability and require caution when used for diagnosing iron status in CKD patients. Reticulocyte hemoglobin content and the percentage of HRC are more powerful, but their widespread use is hampered by the issue of sample stability in storage. sTfR and hepcidin show promise, but require further investigation as well as the development of standardized, low-cost assay platforms.