Laboratory diagnosis of anemia: are the old and new red cell parameters useful in classification and treatment, how?

Transcription

1 International Journal of Laboratory Hematology REVIEW ARTICLE The Official journal of the International Society for Laboratory Hematology INTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY Laboratory diagnosis of anemia: are the old and new red cell parameters useful in classification and treatment, how? M. BUTTARELLO Clinical Pathology Laboratory, Hospital of Adria, Adria (RO), Italy correspondence: Mauro Buttarello, Clinical Pathology Laboratory, Hospital of Adria, ULSS 19 Piazza degli Etruschi, Adria (RO), Italy. Tel.: ; doi: /ijlh accepted for publication 4 April 2016 Keywords Anemia, red cell indices, reticulocytes, immature reticulocyte fraction, reticulocyte hemoglobin content, mean reticulocyte volume SUMMARY Introduction: Anemia is a global problem affecting the population in both developing and developed countries, and there is a debate on which hemoglobin level limit should be used to define anemia in general population and particularly in the elderly. We present herein a laboratory approach to diagnosing the possible causes of anemia based on traditional and new erythroid parameters. In this article, we provide practical diagnostic algorithms that address to differential diagnosis of anemia. Based on both morphological and kinetic classifications, three patterns were considered: microcytic, normocytic, and macrocytic. Methods: Main interest is on the clinical usefulness of old and new parameters such as mean cell volume (MCV), red blood cell distribution width (RDW), hypochromic and microcytic erythrocytes, immature reticulocyte fraction (IRF), and some reticulocyte indices such as reticulocyte hemoglobin content and mean reticulocyte volume. The pathophysiologic basis is reviewed in terms of bone marrow erythropoiesis, evaluated by reticulocyte count (increased or normal/decreased) and IRF. The utility of reticulocyte indices in the diagnosis of iron-deficient erythropoiesis (absolute or functional) and in monitoring of response to treatment in nutritional anemia (iron and cobalamin) was also investigated. Results: For each parameter, the availability, the possible clinical applications, and the limitations were evaluated. A discussion on intraindividual biological variation and its implication on the usefulness of conventional reference intervals and in longitudinal monitoring of the patients was also reported. Conclusion: Red cell parameters and reticulocyte indices play an essential role in differential diagnosis of anemia and in its treatment. More efforts are needed in harmonizing parameters whose results are still too different when produced by different analyzers. 123

2 124 M. BUTTARELLO LABORATORY DIAGNOSIS OF ANEMIA INTRODUCTION Anemia is when blood hemoglobin (Hb) concentration is below the lower limit of the reference interval stated for age, sex, race, and altitude. The commonly accepted lower limits for adult population are the WHO criteria suggested by an expert committee nearly 50 years ago: 130 g/l in men and 120 g/l in women, without the distinction between age and race (1). The definition of anemia has attracted interest in recent years because epidemiologic studies suggest that anemia may be associated with poor prognosis in many different diseases, particularly among aged people. A recent large population survey based on WHO criteria (NHANES-III) (2) showed that nearly ten percent of men and woman older than 65 years were anemic. These percentages rose to 26% in males and 20% in females older than 85. It is not clear whether the difference in lower limits, justified in androgendependent age, should be continued after 65 years of age. Many of these subjects were apparently healthy, and in most cases, clinical investigations did not uncover a specific cause of anemia. These results suggest that somewhat lower limits than normal might be used in the elderly. Nevertheless, the too easy acceptance of mild anemia as physiologic in the elderly runs the risk of ignoring an underlying disease. There is a debate on which hemoglobin lower limit should be used to define anemia in general population and particularly in the elderly (3). Two different, relatively recent, large databases (NHANES-III and Scripps-Kaiser) (4, 5) in which the hemoglobin determination was carried out with standardized automated methods obtained a good agreement and new lower limits are proposed (6). It would seem that these limits (5% of normal distribution) are 137 g/l in white men (20 59 years) and 132 g/l for men after the age of 60; the corresponding value for women is 122 g/l independently of age. In Afro-Americans, these limits are lower: 129 g/l in younger men and 127 g/l in men older than 60, while the corresponding value for women is 115 g/l at all ages. For many practical approaches, a decrease in hematocrit (Hct) is considered equivalent to a decreased hemoglobin concentration, but this simplification is not always correct. All hematology impedance-based analyzers falsely overestimate Hct in erythrocytes with a high mean hemoglobin concentration (MCHC) and underestimate Hct in hypochromic red cells. In this last condition, the use of Hct rather than the more accurate measured Hb can overestimate the diagnosis of anemia in subjects with iron deficiency (7). Also, the opticalbased instruments with isovolumetric sphering provide a falsely elevated Hct when they analyze sickle red cells that cannot be sphered. A typical artifactual dissociation with all the automated analyzers between Hb result (usually correct) and Hct (underestimated) is the presence of red blood cell (RBC) agglutinates. Because the upper volumetric threshold to consider cells as RBC is between 200 and 300 fl according to the analyzer, the large RBC clumps are not counted as RBC. This causes a spuriously low RBC count and low Hct. In contrast, Hb is measured after RBC lysis and is unaffected by agglutinins. As a consequence, MCHC is abnormally high, usually greater than 360 g/l. Moreover, also Hb can be erroneously overestimated, although more rarely, in subjects with severe hypertriglyceridemia or receiving an intravenous administration of fat emulsions, or with high WBC counts, due to the excessive turbidity. OLD ERYTHROCYTE INDICES Maxwell Wintrobe 80 years ago proposed the anemia classification based on the mean cell volume (MCV) obtained by Hct/RBC ratio from the measurement of spun Hct and manual hemocytometric RBC count. The MCHC was calculated as Hb/Hct ratio, where Hb was also based on manual measure (8). Of these two indices, which allowed to classify the anemia as microcytic, normocytic, and macrocytic based on MCV value and hypochromic, normochromic or hyperchromic based on MCHC, only MCV has survived as key parameter for the classification of anemia with automated hematology analyzers (Figures 1 3). With the data collected on a cell-by-cell basis, modern instruments generate a histogram of erythrocytes size distribution. From this histogram, an index of heterogeneity referred to as red cell distribution width (RDW) can be determined. This is almost always expressed as percentage coefficient of variation and, less frequently, as standard deviation. The possibility of a quantitative, nonsubjective measurement of an anisocytosis index has rewakened interest. Bessman et al. (9) in the early 1980 proposed a classification of anemia based on both MCV and RDW: homogeneous (with normal RDW) and heterogeneous (with

3 M. BUTTARELLO LABORATORY DIAGNOSIS OF ANEMIA 125 MICROCYTIC ANEMIA (MCV < 80 fl) Re culocyte count ( X 10 9 /L) NORMOCYTIC ANEMIA (MCV fl) Re culocyte count ( X 10 9 /L) Normal or decreased Normal or decreased Re culocyte hemoglobin content / re culocyte volume (< 28 pg / < 100 fl) Decreased % Hypochromic RBC % Microcy c RBC Re culocyte hemoglobin content / re culocyte volume (< 28 pg / < 100 fl) Decreased - Anemia of renal insufficiency - Anemia of chronic diseases - Acute infec ons - Primary bone marrow disorders - Aplas c anemia Markers sugges ve of hemolysis: Haptoglobin, LDH, bilirubin Peripheral blood smear Markers not sugges ve of hemolysis Blood loss - βthalassemia trait - Iron deficiency - Chronic diseases % Micro / % Hypo ra o - Early response to iron treatment - βthalassemia Other findings (not diagnos c): consider - Membrane defect: PNH - Enzymopathy (G6PDH, PK) - Hemoglobinopathy Fragmented erythrocytes Microangiopathy Spherocytosis Decreased Iron deficiency β-thalassemia trait Direct Coombs test posi ve - Autoimmune hemoly c anemia - Cold agglu nin disease Direct Coombs test nega ve - Hereditary spherocytosis Biochemical markers: ferri n, %TSAT, HbA 2 /hemoglobin analysis Figure 2. Diagnostic algorithm for normocytic anemia - Absolute iron deficiency - Func onal iron deficiency - Chronic diseases Figure 1. Diagnostic algorithm for microcytic anemia. increased RDW) erythrocyte population. The former includes hypoproliferative anemia, marrow aplasia, and thalassemia heterozygosity; the latter includes nutritional anemias (iron, cobalamin, and folic acid deficiency) and sideroblastic anemia. Although this approach was largely accepted and RDW was added to routine analysis in many laboratories, numerous exceptions began to be observed. There is a wide distribution of RDW values within a given disease, whose usefulness in differential diagnosis has decreased, but its utility as a general marker of abnormality has been maintained. A further complication derives from the difference in reference intervals obtained with analyzers from different manufacturers (10 12). This is explained by the different algorithms used to cut the tails of distribution, which is needed to eliminate extreme values often due to artifacts. The mean hemoglobin content (MCH), which is strongly correlated with MCV, is calculated as Hb/RBC ratio. These last measurements with automated analyzers are more accurate and precise than MCV, which is derived by a direct measurement of a single cell size using different analytical methods (impedance with or without hydrodynamic focusing, or light scattering). Moreover, MCV, different from MCH, is affected by preanalytical variables such as storage temperature and time. A dissociation between MCV and MCH was recently described (13): high MCV and low MCH. This was the case of macrocytic hypochromic anemia, indicating the coexistence of both macrocytosis due to cobalamin/folate deficiency and hypochromia due to hemoglobin E disease. Inappropriately low MCH with a high MCV can be found also in anemia due to B12 (or folate) and iron deficiency (or thalassemia). NEW RED CELL PARAMETERS Some hematology analyzers can quantitate the percentage of hypochromic, microcytic, and more rarely

4 126 M. BUTTARELLO LABORATORY DIAGNOSIS OF ANEMIA Normal or decreased Immature re culocyte frac on Normal or decreased MACROCYTIC ANEMIA (MCV > 100 fl) Re culocyte count ( X 10 9 /L) Immature re culocyte frac on hyperchromic cells is useful in the diagnosis of spherocytosis either by hereditary or by immune hemolysis (21, 22). The main limit in the use of these parameters is due to the fact that they are affected by temperature and storage time. In fact, erythrocytes in the samples stored at room temperature tend to progressively swell, with a consequent reduction in cellular hemoglobin concentration and an increase in hypochromic and decrease in hyperchromic RBC%. Peripheral blood smear - Round macrocytes - No hypersegmenta on of neutrophils Nonmegaloblas c macrocytosis - Hypothyroidism - Myelodysplas c syndromes - Liver diseases - Alcohol chronic abuse - Myelodysplas c syndromes - Acute infec ons - Oval macrocytes - Hypersegmenta on of neutrophils Megaloblas c macrocytosis - B12 or folate deficiency - Therapy (hydroxyurea, zidovudine, methotrexate,..) - Hemorrhage - Hemolysis - Response to B12 / folate treatment EVALUATION OF BLOOD SMEAR All the red blood cell indices, although useful, are the representation of the mean and overall dispersion of the erythroid cellular population and provide little information about specific red blood cell shapes or the presence of minor populations of abnormal cells. Examination of blood smear for some specific shapes as reported in Figures 2 and 3 can provide a valuable information to aid in the diagnosis of the underlying disease. Figure 3. Diagnostic algorithm for macrocytic anemia. hyperchromic erythrocytes (Table 1). In iron-deficient erythropoiesis, a greater fraction of RBC is hypochromic rather than microcytic, and the microcytic/hypochromic ratio shows the best diagnostic efficiency in the differential diagnosis with beta-thalassemia trait (14, 15). Many other discriminant algorithms have been recently proposed including conventional and new RBC parameters (15, 16). The results were in general better than the traditional discriminant functions, but the performance of any index seems to depend on the geographical origin of the population in which it is applied (17). Recent studies have shown that hypochromic erythrocytes are useful in identifying iron-restricted erythropoiesis in anemic patients treated with erythropoiesis-stimulating agents (ESAs), particularly anemia of the chronic kidney disease or in hemodialyzed patients. The response to ESAs is strictly dependent on iron availability and is limited by iron deficiency that can be absolute or functional (i.e., limitation of bone marrow erythropoietic activity by the inability to mobilize the sufficient iron from body storage sites) (18 20). The presence of RETICULOCYTE AND IMMATURE RETICULOCYTE FRACTION In addition to red cell indices and morphological criteria, anemia may be classified by kinetic approach, that is, the degree of bone marrow response evaluated by the reticulocyte count. The reticulocyte count is clinically important both for the pathophysiological classification of anemia (due to an inadequate production of erythrocytes by the bone marrow, in which case there is a decreased number of reticulocytes, or to an excessive loss or the destruction of erythrocytes, in which there is an increase in reticulocyte count) and for the early identification of the normalization of erythropoiesis by the marrow after therapeutic intervention (iron, cobalamin, folic acid, ESAs, etc.), after spontaneous or pharmacologically induced aplasia of the marrow, or following bone marrow transplantation. However, the imprecision of the manual microscopic method (coefficient of variation (CV) between 68.6% at low concentration and 16% at high level) (23) makes it almost useless mainly in severe reticulocytopenia. It does not allow for the observation of small but significant variations during the early recovery of erythropoietic bone marrow activity, nor does it clearly define the difference between normal and

5 M. BUTTARELLO LABORATORY DIAGNOSIS OF ANEMIA 127 Table 1. Old and new RBC parameters and their clinical applications Parameter Availability Proposed clinical applications Limitations References Old RBC parameters Mean cell volume (MCV) (fl) Mean cell hemoglobin content (MCH) (pg) Mean cell hemoglobin concentration (MCHC) (g/ L) Red cell distribution width (RDW) (%) New RBC parameters All the analyzers Anemia classification based on morphological approach All the analyzers Useful when hemoglobin synthesis is impaired as in iron deficiency anemia All the analyzers in spherocytosis because of a reduced surface/volume ratio All the analyzers Generic marker of abnormality when increased Affected by preanalytical variables (storage temperature, time) 8, 45 Highly correlated with MCV 13, 46 With some impedance analyzers, the value is clamped around the mean Of little usefulness in the differential diagnosis of anemia. Reference intervals are method dependent 7, Percentage of hypochromic red cells Percentage of hyperchromic red cells Hypo% (Siemens Advia 2120); %Hypo-He (Sysmex XE/XN); % HPO (Abbott Sapphire); LHD% (Beckman-Coulter LH/DxH 800). Hyper% (Siemens Advia 2120); % Hyper-He (Sysmex XE/XN); %HPR (Abbott Sapphire). Assessment of iron availability (absolute or functional) for erythropoiesis. Related to iron status in the last 3 months. Diagnosis of hereditary/ immune spherocytosis Affected by preanalytical variables (storage temperature, time). Reference intervals and diagnostic thresholds are method dependent. Limited value in the presence of b- thalassemia. Reference intervals and diagnostic thresholds are method dependent. 18, 19, 48, 49 21, 22 (continued)

6 128 M. BUTTARELLO LABORATORY DIAGNOSIS OF ANEMIA Table 1. (Continued) Parameter Availability Percentage of microcytic red cells Reticulocyte parameters Micro% (Siemens Advia 2120); % micro-r (Sysmex XE/ XN); %MIC (Abbott Sapphire). Proposed clinical applications Limitations References Useful in combination with other RBC parameters (mainly hypochromic erythrocytes) to obtain discriminant indices for the differential diagnosis of microcytic anemia. Reference intervals and diagnostic thresholds are method dependent Immature reticulocyte fraction (IRF) (fraction) Reticulocyte mean hemoglobin content (pg) Mean reticulocyte volume (fl) All the analyzers Classification of anemias and monitoring of treatment. Verify aplastic anemia. CHr (Siemens Advia 2120); Ret-He (Sysmex XE/XN); MCHr (Abbott Sapphire); RHE (Mindray BC 6800); RHCc (ABX-Horiba Pentra Nexus DX) MCVr (Siemens Advia 2120); MCVR (Abbott Sapphire); MVR (Mindray BC 6800); MRV (ABX-Horiba Pentra Nexus DX); MRV (Beckman- Coulter LH/DxH 800). Diagnosis of iron-deficient erythropoiesis. Early monitoring the response to iron therapies. Diagnosis of iron-deficient erythropoiesis. Early monitoring of treatment with B12/folate/iron in nutritional anemia. Reference intervals and diagnostic cutoff are method dependent. Limited value in the presence of a- or b- thalassemia. Affected by preanalytical variables (storage temperature, time). Reference intervals strictly method dependent , 37, 40

7 M. BUTTARELLO LABORATORY DIAGNOSIS OF ANEMIA 129 low reticulocyte levels. Automated analyzers represent a revolution for this cell type using dyes to bind reticulocyte RNA and flow cytometers to perform rapid and objective counts. The possibility to analyze tens of thousands of cells per sample has reduced imprecision (CV between 25% at low concentration and 3.0% at high counts) (24) (M. Buttarello, personal observations). Furthermore, using an absolute reticulocyte count (expressed as the number of cells per unit of volume: x 10 9 /L) rather than proportion no longer requires correction for reduced hemoglobin concentrations. A little complication derives from the differences in the reference intervals that are strictly method dependent (lower limit of the 95% interval between 19 and /L and upper between 85 and /L) (24). What has created an additional interest about automated reticulocyte analysis is the availability of a new parameter called immature reticulocyte fraction (IRF) based on reticulocytes RNA content (25). Reticulocytes originate from orthochromatic erythroblasts following ejection of the nucleus, and they gradually mature, partly in the marrow (3 days on average) and partly in the peripheral blood (1 day). Reticulocytes gradually lose their RNA and ultimately become RNA-free red cells, while some RNA-rich, more immature reticulocytes are found in relatively narrow proportion in the peripheral blood of the healthy subjects. There are, however, various expressions according to the analyzer used, and thus, the reference intervals are different (low level between and 0.20 and high level between 0.14 and 0.40) (26, 27). Independently by the way on as it is produced, the IRF is an early and sensitive index of erythropoiesis; in fact, immature reticulocytes appear in a larger proportion when red cell production increases. The IRF has a weak but significantly positive correlation with the absolute reticulocyte count, indicating that it is an additional useful parameter to evaluate the erythropoietic activity. The greatest clinical usefulness, especially in the classification of anemia based on marrow response, is found using two-dimensional matrices of IRF vs. the absolute reticulocyte count (25, 26). With covariance analysis (AN- COVA), it is possible to identify some well-differentiated behaviors in certain areas of the matrices: (i) In reticulocytopenia, there is no covariance, both in marrow aplasia and in early erythropoietic response; (ii) in normal or mild reticulocytosis, there are two subsets with positive covariance corresponding to the healthy subjects and to accelerated erythropoiesis; (iii) for marked reticulocytosis, the covariance is negative, suggesting a gradual deceleration of erythropoiesis (28). Therefore, IRF and reticulocyte count may vary in a concordant or independent way according to the erythropoietic conditions and can be hypothesized the IRF as an index of acceleration and the absolute reticulocyte count as a quantitative measure of the effectiveness of erythropoiesis (28, 29). This parameter is therefore useful in distinguishing (i) anemia characterized by an increase in erythropoiesis, like acquired hemolytic anemias or the loss of blood, which produces an increase both in total reticulocytes and in IRF; (ii) anemias due to the reduced marrow production (i.e., chronic renal disease) in which both values are found to be decreased, and (iii) anemia of acute infections or myelodysplastic syndromes in which there is a dissociation between total reticulocyte count (reduced or normal) and the IRF which can be increased (30 33). Other uses include monitoring the therapy efficacy in nutritional anemia (e.g., cobalamin, folates, and iron) because the increase in IRF precedes the increase in total reticulocyte count by several days. In subjects with iron-deficient anemia treated with iv iron, it increased at day 1 and continued to increase until reaching the maximum value at day 5 (34). This value was correlated with the erythropoietin concentration at the beginning of therapy (M. Buttarello, data not published). The combination of reticulocyte count > /L with a reticulocyte count/irf ratio >7.7 is considered useful for the screening of trait and mild hereditary spherocytosis (35). RETICULOCYTE INDICES The latest generation of hematology analyzers provides some reticulocyte indices analogous to the equivalent RBC indices (Table 1). Among these, the most promising from a clinical point of view are the hemoglobin content of reticulocyte and the mean reticulocyte volume. The hemoglobin content, which directly reflects the synthesis of hemoglobin in marrow precursors, is a measure of adequacy of iron availability (34, 36 38). This parameter is important because its reduction indicates iron-deficient erythropoiesis, even in conditions in which traditional

8 130 M. BUTTARELLO LABORATORY DIAGNOSIS OF ANEMIA INTRAINDIVIDUAL BIOLOGICAL VARIATION Hb (g/l) CHr (pg) END (IV) IRON DAYS START (OS) IRON THERAPY THERAPY START (IV) IRON THERAPY Ferr µg/l : 5.7 Ferr µg/l : 3.4 Ferr µg/l : 74 Ferr µg/l : 43 Iron µmol/l : 3.58 Iron µmol/l : 3.22 Iron µmol/l : 12.0 Iron µmol/l : 8.24 TRF g/l: 3.71 TRF g/l: 3.50 TRF g/l: 3.41 TRF g/l: 2.73 Figure 4. Response in hemoglobin concentration (Hb), reticulocyte hemoglobin content (CHr), and reticulocyte% (Siemens Advia 120 analyzer) to intravenous (iv) iron administration in a patient unresponsive to oral iron therapy. Ferr: serum ferritin concentration; Iron: serum iron concentration; TRF: serum transferrin concentration RETICULOCYTES (%) CH r Hb RET % One source of variability of clinical laboratory results (besides preanalytic and analytic variations) is the intraindividual variation around the homeostatic setting point (41). Several studies have investigated this biological variation and the results are similar even if carried out at different time points and in different geographical areas (42 44). The reported values varied between 1.9 and 2.8% for Hb and Hct; between 0.6 and 1.3% for MCV; and between 5.8 and 9.5% for reticulocytes. From these values, an index of individuality as ratio of intraindividual to interindividual coefficient of variation can be calculated. For the above-mentioned parameters, it is between 0.19 and 0.42 for Hb, between 0.17 and 0.27 for MCV, and between 0.18 and 0.30 for reticulocytes, according to the different studies. A low index of individuality (<0.5) indicates that conventional reference intervals may be of little usefulness, especially when deciding if the change observed in a subject is clinically biochemical markers such as ferritin and transferrin saturation are inadequate (e.g., in inflammations or anemia from a chronic disease), and besides, it is useful for monitoring early response to intravenous iron therapy because it increases significantly after only h (Figure 4) (34, 36). Exceptions are heterozygotes for beta-thalassemia whose reticulocyte hemoglobin content is found to be always reduced independently of iron stores (39). Low values of this index are indicative even in functional iron deficiency which appears in patients treated with erythropoietin (38). Few studies are available on the clinical usefulness of mean reticulocyte volume. In subjects with depleted iron stores, this index increases rapidly following iron therapy and decreases equally as rapidly with the development of iron-deficient erythropoiesis. The reticulocyte volume decreases dramatically and reticulocytes are smaller than the circulating RBCs, in nutritional macrocytosis after therapy with vitamin B12 and/or folic acid (Figure 5) (37). The main limit of the use of these indices is the difficulty to compare numeric results obtained from the analyzers of different manufacturers (the lower limit of the 95% interval between 91 and 100 fl and the upper limit between 111 and 120 fl) (40). CHr (pg) MCVr (fl) Hb (gl) MCVr CHr RET % DAYS START OF COBALAMIN (IV) THERAPY Hb g/l START OF IRON (IV) THERAPY Figure 5. Changes in mean reticulocyte volume (MCVr), reticulocyte hemoglobin content (CHr), reticulocyte % and hemoglobin concentration (Hb) (Siemens Advia 120 analyzer) to intravenous cobalamin administration, followed by intravenous iron due to the functional iron deficiency development. MCVr and CHr decreased significantly after iv cobalamin therapy. The excessive decrease in CHr suggests an iron deficiency, promptly corrected by iv iron administration RETICULOCYTES (%)

9 M. BUTTARELLO LABORATORY DIAGNOSIS OF ANEMIA 131 remarkable. Useful in serial monitoring of physiologic or pathologic conditions is the critical difference (called also reference change value: RCV), which defines the percentage change that should be exceeded (given the analytic and intraindividual biological variations) so that there is a significant difference between two consecutive measurements. The significant percentage changes (for probabilities of 95%) for the named red cell parameters are (43, 44) as follows: between 6.22 and 6.82% for Hb and Hct, between 2.35 and 3.12% for MCV, and between 36.7 and 41.7% for reticulocytes. Differences depend on biological variation (42 44) and on the analytical variability of analyzers, and these differences are smaller for instruments with smaller imprecision. CONCLUSIONS Red cell parameters and reticulocyte indices play an essential role in the differential diagnosis of anemia and in its treatment. More efforts are needed in harmonizing parameters whose results are still too different when produced by different analyzers. Moreover, it should be remembered that despite the essential role of automation, microscopic control of pathologic samples remains indispensable. COMPETING INTERESTS The author has no competing interest. REFERENCES 1. Blanc B, Finch CA, Hallberg L, Herbert V, Lawkowicz W, Layrisse M, Mollin DL, Rachmilewitz M, Ramalingaswami V, Sanchez-Medal M, Wintrobe MM. Nutritional anaemias. Report of a WHO Scientific Group. World Health Organ Tech Rep Ser 1968;405: Guralnik JM, Eisenstaedt RS, Ferrucci L, Klein HG, Woodman RC. Prevalence of anemia in persons 65 years and older in the United States: evidence for a high rate of unexplained anemia. Blood 2004;104: Schrier SL. Hematology, ASH, and the anemia of the aged. Editorial. Blood 2005;106: Cheng CK, Chan J, Cembrowski GS, Van Assendelft OW. Complete blood count reference interval diagrams derived from NHANES III: stratification by age, sex, and race. Lab Hematol 2004;10: Waalen J, Felitti VJ, Gelbart T, Ho NJ, Beutler E. Penetrance of hemochromatosis. Blood Cell Mol Dis 2002;29: Beutler E, Waalen J. The definition of anemia: what is the lower limit of normal of the blood hemoglobin concentration? Perspective Blood 2006;107: Mohandas N, Clark MR, Kissinger S, Bayer C, Shohet SB. Inaccuracies associated with the automated measurement of mean cell hemoglobin concentration in dehydrated cells. Blood 1980;56: Wintrobe MM. Anemia: classification and treatment on the basis of differences in the average volume and hemoglobin content of the red corpuscles. Arch Intern Med 1934;54: Bessman JD, Gilmer PRjr, Gardner FH. Improved classification of anemias by MCV and RDW. Am J Clin Pathol 1983;80: Van den Bossche J, Devreese K, Malfait R, Van de Vyvere M, Wauters A, Neels H, De Schouwer P. Reference intervals for a complete blood count determined on different automated haematology analysers: ABX Pentra 120 retic, Coulter Gen-S, Sysmex SE 9500, Abbott Cell Dyn 4000, and Bayer ADVIA 120. Clin Chem Lab Med 2002;40: Buttarello M, Plebani M. Automated blood cell counts. State of the art. Am J Clin Pathol 2008;130: Lippi G, Pavesi F, Bardi M, Pipitone S. Lack of harmonization of red blood cell distribution width (RDW). Evaluation of four hematological analyzers. Clin Biochem 2014;47: Hazarika B. What is missed in an automated count? (Images in Hematology). Blood 2012;120: d Onofrio G, Zini G, Ricerca BM, Mancini S, Mango G. Automated measurement of red blood cell microcytosis and hypochromia in iron deficiency and beta-thalassemia trait. Arch Pathol Lab Med 1992;116: Urrechaga E. Red blood cell microcytosis and hypochromia in the differential diagnosis of iron deficiency and beta thalassemia trait. Int J Lab Hematol 2009;31: Schoorl M, Schoorl M, Linssen J, Martinez Villanueva M, Velasco NoGuera JA, Hernandez Martinez P, Bartels PCM. Efficacy of advanced discriminating algorithms for screening on iron-deficiency anemia and b-thalassemia trait. A multicenter evaluation. Am J Clin Pathol 2012; 138: Hoffman JJML, Urrechaga E, Aguirre U. Discriminant indices for distinguishing thalassemia and iron deficiency in patients with microcytic anemia: a metaanalysis. Clin Chem Lab Med 2015;53: Buttarello M, Pajola R, Novello E, Rebeschini M, Cantaro S, Oliosi F, Naso A, Plebani M. Diagnosis of iron deficiency in patients undergoing hemodialysis. Am J Clin Pathol 2010;133: Macdougall IC, Cavill I, Hulme B, Bain B, McGregor E, McKay P, Sanders E, Coles GA, Williams JD. Detection of functional iron deficiency during erythropoietin treatment: a new approach. Br Med J 1992;304: WayneThomas D, Hinchliffe RF, Briggs C, Macdougall IC, Littlewood T, Cavill I, on behalf of British Committee foe Standards in Haematology. Guideline for the laboratory diagnosis of functional iron deficiency. Br J Haematol 2013;161: Gilsanz F, Ricard P, Millan I. Diagnosis of hereditary spherocytosis with dual-angle differential light scattering. Am J Clin Pathol 1993;100: Conway AM, Vora AJ, Hinchliffe RF. The clinical relevance of an isolated increase in the number of circulating hyperchromic red blood cells. J Clin Pathol 2002;55:

10 132 M. BUTTARELLO LABORATORY DIAGNOSIS OF ANEMIA 23. Buttarello M, Bulian P, Venudo A, Rizzotti P. Laboratory evaluation of the Miles H.3 automated reticulocyte counter. A comparative study with manual reference method and Sysmex R Arch Pathol Lab Med 1995;119: Buttarello M, Bulian P, Farina G, Temporin V, Toffolo L, Trabuio E, Rizzotti P. Flow cytometry reticulocyte counting. Parallel evaluation of five fully automated analyzers: an NCCLS-ICSH approach. Am J Clin Pathol 2001;115: Davis BH. Immature reticulocyte fraction (IRF): by any name, a useful clinical parameter of erythropoietic activity. Lab Hematol 1996;2: Buttarello M, Bulian P, Farina G, Petris MG, Temporin V, Toffolo L. Five fully automated methods for performing immature reticulocyte fraction. Comparison in diagnosis of bone marrow aplasia. Am J Clin Pathol 2002;117: Piva E, Brugnara C, Chiandetti L, Plebani M. Automated reticulocyte counting: state of the art and clinical applications in the evaluation of erythropoiesis. Clin Chem Lab Med 2010;48: Buttarello M, Bulian P, Farina G, Temporin V, Toffolo L. Frazione di reticolociti immaturi (IRF) e conteggio reticolocitario assoluto: analisi multivariata e studio della covarianza in diversi subsets eritropoietici (Abstract). Riv Med Lab (JLM) 2000;1 (suppl 1): d Onofrio G, Kuse R, Foures C, Jou JM, Pradella M, Zini G. Reticulocytes in haematological disorders. Clin Lab Haematol 1996;18(suppl 1): Tsuda I, Tatsumi N. Maturity of reticulocytes in various hematological disorders. Eur J Haematol 1989;43: Davis B, Bigelow N. Automated reticulocyte analysis Clinical practice and associated new parameters. Hematol/Oncol Clin North Am 1994;8: Chang C, Kass L. Clinical significance of immature reticulocyte fraction determined by automated reticulocyte counting. Am J Clin Pathol 1997;108: Torres Gomez A, Casano J, Sanchez J, Madrigal E, Blanco F, Alvarez MA. Utility of reticulocyte maturation parameters in the differential diagnosis of macrocytic anemia. Clin Lab Haematol 2003;25: Buttarello M, Temporin V, Ceravolo R, Farina G, Bulian P. The new reticulocyte parameter (Ret-y) of the Sysmex XE Its use in the diagnosis and monitoring of posttreatment sideropenic anemia. Am J Clin Pathol 2004;121: Mullier F, Lainey E, Fenneteau O, Da Costa L, Schillinger F, Bailey N, Cornet Y, Chatelain C, Dogne JM, Chatelain B. Additional erythrocytic and reticulocytic parameters helpful for diagnosis of hereditary spherocytosis: results of a multicentre study. Ann Hematol 2011;90: Brugnara C, Laufer MR, Friedman AR, Bridges K, Platt O. Reticulocyte hemoglobin content (CHr): early indicator of iron deficiency and response to therapy. Blood 1994;83: d Onofrio G, Chirillo R, Zini G, Caenaro G, Tommasi M, Micciulli G. Simultaneous measurement of reticulocyte and red cell indices in healthy subjects and patients with microcytic and macrocytic anemia. Blood 1995;85: Brugnara C. Reticulocyte cellular indices: a new approach in the diagnosis of anemias and monitoring of erythropoietic function. Crit Rev Clin Lab Sci 2000;37: Noronha JFA, Grotto HZW. Measurement of reticulocyte and red blood cell indices in patients with iron deficiency anemia and b-thalassemia. Clin Chem Lab Med 2005;43: Cappelletti P, Biasioli B, Buttarello M, Bulian P, Casolari B, Cenci A, Miconi V. Mean reticulocyte volume (MCVR): reference intervals and the need for standardization (abstract). Proceeding of the XIX International Symposium on Technological Innovation in Laboratory Hematology, ISLH. Amsterdam, the Netherlands; April 25-28, 2006: Ricos C, Alvarez V, Cava F, Garcia-Lario JV, Hernandez H, Jmenez CV, Minchinela J, Perich C, Simon M. Current databases on biological variation: pros, cons, and progress. Scand J Clin Lab Invest 1999;59: Buttarello M, on behalf of the hematology study group of the Italian Society of Laboratory Medicine. Variabilita biologica dei parametri ematologici. Riv Med Lab (JLM) 2003;4(suppl 1): Zhang P, Tang H, Chen K, Chen Y, Xu D. Biological variations of hematologic parameters determined by UniCelDxH 800 hematology analyzer. Arch Pathol Lab Med 2013;137: Cappelletti P, Biasioli B, Buttarello M, Bulian P, Casolari B, Cenci A, Miconi V. Within and between subject biological variability in complete blood count (CBC), leukocyte differential count (LDC), and reticulocytes (abstract). Proceeding of the XIX International Symposium on Technological Innovation in Laboratory Hematology, ISLH. Amsterdam, the Netherlands; April 25-28, 2006: Zini G. Stability of complete blood count parameters with storage: toward defined specifications for different diagnostic applications. Editorial. Int J Lab Hematol 2014;36: Brugnara C, Mohandas N. Red cell indices in classification and treatment of anemias: from M.M. Wintrobe s original 1934 classification to the third millennium. Curr Opin Hematol 2013;20: Van Hove L, Schisano T, Brace L. Anemia diagnosis, classification, and monitoring using Cell-Dyn technology reviewed for the new millennium. Lab Hematol 2000;6: Urrechaga E, Unceta M, Borque L, Escanero JF. Low hemoglobin density potential marker of iron availability. Int J Lab Hematol 2012;34: Hoffmann J, van den Broek N, Curver J. Reference intervals of extended erythrocyte and reticulocyte parameters. Clin Chem Lab Med 2012;50: Fraser CG, Wilkinson SP, Neville RG, Knox JD, King JF, MacWalter RS. Biologic variation of common hematologic laboratory quantities in the elderly. Am J Clin Pathol 1989;92: