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Year : 2021  |  Volume : 15  |  Issue : 1  |  Page : 13-23

Approach to anemia with caveats in focus

Department of Medicine, University College of Medical Sciences (University of Delhi) and Guru Teg Bahadur Hospital, Delhi, India

Date of Submission28-Oct-2021
Date of Decision04-Jan-2022
Date of Acceptance26-Jan-2022
Date of Web Publication13-Apr-2022

Correspondence Address:
Dr. Amitesh Aggarwal
Department of Medicine, University College of Medical Sciences (University of Delhi) and Guru Teg Bahadur Hospital, Delhi - 110 095
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/upjimi.upjimi_2_21

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Anemia being a very commonly encountered clinical condition can be a presentation of a wide range of underlying illness. This article tries to succinctly provide an approach to and give an overview of anemia without delving into any one particular type. To categorize anemia would help narrow down the list of differentials and enable diagnosing a large and varied number of conditions.

Keywords: Anemia, approach, functional classification, red blood cells morphology, reticulocyte count

How to cite this article:
Aggarwal A, Thakur SK. Approach to anemia with caveats in focus. J Intern Med India 2021;15:13-23

How to cite this URL:
Aggarwal A, Thakur SK. Approach to anemia with caveats in focus. J Intern Med India [serial online] 2021 [cited 2023 Mar 24];15:13-23. Available from: http://www.upjimi.com/text.asp?2021/15/1/13/343026

  Introduction Top

Anemia refers to decrease in the oxygen-carrying capacity of blood either due to decrease in the amount of hemoglobin (Hb) or its dysfunction. Anemia is not a diagnosis but a presentation of underlying conditions ranging from a simple nutritional deficiency to underlying malignancy.[1]

Anemia is a condition that medical professionals encounter from their initial clinical exposure days and it remains pertinent irrespective of the years or specialty they end up with. Hence, developing a comprehensive approach to a patient presenting with anemia would help us to narrow down the possible diagnosis and initiate appropriate care.

[TAG:2]Physiologic Basis of Red Cell Production[2][/TAG:2]

Erythroid cells come from a common erythroid/megakaryocyte progenitor. Daily replacement of 0.8%–1% of all circulating red cells occurs, as the average life span of red cells is around 100–120 days.

Erythron (the dynamic organ responsible for red cell production) includes marrow erythroid precursor cells as well as the mature circulating red blood cells (RBCs). Its functional capacity depends on presence of normal renal production of erythropoietin, functioning erythroid marrow, and adequate supply of substrates required for erythropoiesis.

Primary regulatory hormone (physiological regulator) of red cell production is erythropoietin (normal level: 10–25 U/L and t1/2 in circulation is around 6–9 h). Produced mainly from peritubular capillaries in kidneys, it is required for the maintenance of committed erythroid progenitor cells. Exogenous erythropoietin (EPO) gene regulation occurs by (hypoxia-inducible factor-1α and availability of oxygen in tissues is the main stimulus for EPO production. Semilogarithmic relation between erythropoietin response (log) and the degree of anemia (linear) exists such that levels increase in proportion to the severity of anemia when Hb concentration falls below 10–12 g/dL.

EPO as a drug increases early progenitor cell numbers and EPO stimulation increases red cell production by 4–5 times within 1–2 week.


  • Reduction in one or more of the major RBC measurements (Hb, hematocrit [Hct] or packed cell volume and RBC count)
  • Qualitative or quantitative diminution of RBC and/or Hb concentration in relation to the standard limit for age and sex.


Cutoff levels for anemia and its severity intended for use in the context of international nutritional studies are [Table 1].
Table 1: Hemoglobin levels to diagnose anemia at sea level (g/dL)[4]

Click here to view

[TAG:2]Clinical Presentation of Anemia[5],[6][/TAG:2]

Common symptoms include weakness, fatigue, lassitude, light headedness, giddiness, fainting/syncope, anorexia, palpitation, breathlessness, anginal pain, insomnia, tinnitus, lack of concentration, intermittent claudication, tingling sensation in extremities, and menstrual irregularities. These are generally seen when moderate or severe anemia develops. Patients with mild anemia may remain asymptomatic.

Acute anemia (blood loss/hemolysis)

Hypovolemia/hypotension dominates the clinical picture.

Mild blood loss-enhanced O2 delivery achieved by changes in O2-Hb dissociation curve (mediated by decreased pH or increased CO2) by Bohr effect prevents symptoms from developing.

Loss of 10%–15% of total blood volume is manifested in the form of vascular instability, hypotension, and decreased organ perfusion. When loss total blood volume exceeds, 30% the body is unable to compensate and the patient prefers to remain in the supine position. Postural hypotension and tachycardia also occur. Signs of hypovolemic shock, confusion, dyspnea, diaphoresis, hypotension, tachycardia, and deficits in vital organ perfusion occur with losses exceeding 40%.

Acute back pain, free Hb in plasma and urine (high colored urine), and features of renal failure indicate an intravascular hemolysis.


Hb or Hct values do not reflect (underestimate) the volume of blood lost. It takes around 36–48 h for these to decline as the blood volume deficit is replaced by the movement of fluid into intravascular compartment or due to fluid resuscitation.

Chronic anemia

Iron deficiency (IDA), B12 def, MDS, compensatory mechanisms such as increased total blood volume slightly, changes in cardiac output and regional blood flow, and increase in intracellular levels of 2,3-BPG prevent symptoms from developing until the Hb is very low.

Shunting of blood away from organs like kidney, gut and skin occurs in chronic anemia

[TAG:2]Points to Note During History Taking[1],[5],[7],[8][/TAG:2]

Present history

Signs and symptoms mentioned above may need to be specially asked for as patients may not report them, thinking of them as insignificant.

Past history

  • Signs and symptoms associated with other disorders or chronic illness associated with anemia such as rheumatoid arthritis (RA), chronic kidney disease (CKD), and tuberculosis (TB) (bleeding, fatigue, malaise, fever, weight loss, night sweats, and other systemic symptoms)
  • Pica is seen in IDA and some psychiatric illness
  • Dysphagia in PlummerVinson syndrome
  • Bleeding from any site and amount, for example. hematemesis/melena/epistaxis/menorrhagia/hemorrhoids
  • Blood transfusion frequency and blood products
  • Episodes of jaundice or anemia exacerbated during acute illnesses or after drug intake
  • Gallstones indicate chronic hemolysis
  • Diarrhea seen in tropical sprue.

Personal history

  • Alcohol consumption
  • Drug and toxin exposure
  • Barefoot walking or fieldwork is associated with infection with parasites.

Menstrual history

  • Amount and frequency of blood loss.

Occupational history

  • Chemical solvent/lead/benzene/insecticide exposure
  • Farmer or field work.

Treatment history

  • Bone marrow suppressant drug
  • Radiation exposure
  • Nonsteroidal anti-inflammatory drugs
  • Hemolysis episodes seen in G6PD-deficient persons after antimalarial drug intake
  • Zinc supplements/denture adhesives cause copper deficiency
  • Previous surgery, for example, bariatric surgery/gastrectomy/ileal surgery/Roux-en-Y procedure lead to malabsorption of vitamins and minerals.

Nutritional/dietary history

  • Pure vegetarian or vegan diet may lead to B12 def
  • Anorexia or dysphagia and poverty may lead to inadequate intake of vitamins and minerals.

Family history

  • Similar illness in family points toward disease with genetic inheritance and effects of shared socioeconomic status, for example, thalassemia, HbE disease, hemophilia, and nutritional deficiencies


Identifying the particular anemic relative as a simple positive family history does not always imply a familial syndrome, for example, females in a family may be anemic or clustering of TB in a crowded living condition causing anemia.

Geographic backgrounds/ethnic origins

  • G6PD deficiency and hemoglobinopathies are common in people of Middle Eastern or African origin
  • β-thalassemia is commonly seen in Punjabis and Sindhis in India.

[TAG:2]Points to Note During Physical Examination[1],[5],[7],[8][/TAG:2]

  • Brittle hair
  • Pale skin and mucous membranes (sites to look for pallor are lower palpebral conjunctiva, tongue [tip and dorsum], soft palate [anemia is noticed here earliest], nail beds, palmar creases [if it is as pale as surrounding skin, it indicates severe anemia], soles, and general skin surface)
  • Glossitis (Vitamin B deficiency, IDA, tropical sprue, pernicious anemia, syphilis, congenital abnormality [median rhomboid glossitis], cirrhosis, and alcoholism)
  • Angular stomatitis/cheilosis in Vitamin B deficiency
  • Nails – brittle; platynychia; koilonychia in IDA; splinter hemorrhages in subacute bacterial endocarditis
  • Finger deformities in rheumatoid arthritis
  • Lemon yellow pallor in advanced pernicious anemia
  • Knuckle pad hyperpigmentation in megaloblastic anemia
  • Edema or anasarca is seen in severe anemia, congestive cardiac failure, renal disorder, hepatic disorder, hypoalbuminemia, and myxoedema
  • Signs suggestive of infection
  • Blood in stool or other orifices
  • Lymphadenopathy hints toward a lymphoproliferative disorder
  • Splenomegaly may be present in lymphoproliferative disorder, tropical infection, and extravascular hemolysis
  • Petechiae indicate a platelet dysfunction
  • Ecchymosis or bruise may be present in hematologic malignancy or aplastic anemia
  • Icterus/dark urine–hemolytic anemia
  • Pale retina.

Cardio vascular system

  • Tachycardia; Strong peripheral pulses
  • Capillary pulsation
  • Cervical venous hum
  • Forceful heartbeat/hyperdynamic apex beat
  • Systolic flow murmur (e.g., hemic murmur in pulmonary area)
  • MS murmur due to functional MI (ring dilatation)
  • Cardiomegaly or heart failure in severe and prolonged anemia.

Respiratory system

  • Basal crepitations.

Nervous system

  • Polyneuropathy.


there are certain situations/conditions where pallor may be present without anemia or it is disproportionate to the severity of anemia such as:

  • Shock/low cardiac output states
  • Conditions leading to vasoconstriction
  • Acute myocardial infarction
  • Severe aortic stenosis/mitral stenosis
  • Vasovagal attack/fear/cold exposure/intense emotion
  • Sheehan's syndrome/panhypopituitarism
  • Thick skin (e.g., scleroderma)
  • Edematous conditions/anasarca
  • Myxedema
  • Chronic renal disease/nephrotic syndrome.

  Laboratory Investigations Top

A large number of investigations and specific tests for each type of anemia are available. But to reach to a probable diagnosis of the cause of anemia, the following tests would be minimum and sufficient.

Complete blood count

  1. RBC count: Hb, Hct, and reticulocyte count
  2. RBC indices: mean cell volume (MCV), mean cell Hb (MCH), mean cell Hb concentration (MCHC), and red cell distribution width (RDW)
  3. WBC count: total count, differential count, and nuclear segmentation of neutrophils
  4. Platelet count
  5. Cell morphology, i.e., peripheral blood smear: cell number, cell size, Hb content, anisocytosis, poikilocytosis, and polychromasia

Iron supply studies

Serum iron, total iron-binding capacity, serum ferritin, transferrin saturation.

Marrow examination

  1. Aspirate: myeloid: erythroid ratio, cell morphology, and iron stain
  2. Biopsy: cellularity and morphology.


  1. Hb electrophoresis
  2. Test for hemolysis: Lactate dehydrogenase (LDH), haptoglobin, direct or indirect antiglobulin test, and Hb in serum and urine
  3. Liver function test (LFT)
  4. Kidney function test (KFT)
  5. Stool examination
  6. Vitamin B12/folic acid/copper levels.

Points to note regarding various tests mentioned above.

Red blood cell count, hemoglobin (directly measured), and hematocrit (calculated) usually change in parallel


  • Hct/Hb ratio may vary according to volume (size) of cells (Normally Hct/Hb around 3)
  • Extreme microcytosis (e.g., thalassemia): RBC count may be increased despite anemia (therefore, RBC count is less preferred to diagnose anemia).

Normal values of Hb, Hct, and RBC vary on the basis of population tested and physiological factors affecting complete blood count such as age, sex, pregnancy, smoking, and altitude

  • Causes of lower values include intense physical activity (dilutional anemia from increased plasma volume, IDA, and march hemolysis), pregnancy (greater increase in plasma volume compared to red cell mass; do not warrant evaluation as long as Hb is ≥11.0, 10.5, and 10.5 g/dL in 1st, 2nd and 3rd trimester, respectively), older age (nutritional deficiencies; kidney disease; anemia of chronic disease/anemia of inflammation [ACD/AI] and unexplained (often myelodysplastic syndromes, it is a diagnosis of exclusion, cytokine mediated), and African-American population compared to Caucasian in Americans.[9],[10],[11]
  • Causes of higher values include smoking or smoke exposure (increased levels of CO→ reduces O2 delivery), hemoconcentration (due to dehydration or hypovolemia. Anemia becomes apparent on volume replacement or with the movement of interstitial fluid into the vascular compartment), high altitude (relative hypoxia), and sexually mature males (effect of androgen).[12],[13],[14]

Reticulocyte count[15]

  • Measures percentage of reticulocytes (immature RBCs) in peripheral blood. Corrected RC percentage or absolute numbers provide a reliable measure of effective red cell production
  • In established anemia, reticulocyte response <2–3 times normal suggests an inadequate marrow response, whereas count >2% means an appropriate bone marrow response
  • Calculation of reticulocyte production index (RPI).

First correction for anemia

  • This correction produces the corrected reticulocyte count
  • It is not done if the reticulocyte count is reported in absolute numbers.

Corrected reticulocyte percentage (absolute reticulocyte count)

= Reticulocyte Percentage (reticulocyte count) × Hct or Hb of the patient

Normal Hct or Hb (45% or 15 g/dL).

Second correction to adjust for longer life of prematurely released reticulocytes in the blood

This correction produces the RPI.

Not done if polychromatophilic cells are not seen on smear.

RPI = Corrected reticulocyte percentage

Maturation correction

Maturation correction of 2 is commonly used [Table 2].
Table 2: Hematocrit percentage and corresponding maturation correction factor[15]

Click here to view

At a normal Hb, reticulocytes are released into circulation with ~1 day left as reticulocyte. But with different severity of anemia, reticulocytes (or even more immature RBC precursors) may be released prematurely.

  • RPI <2 in established anemia means a defect in erythroid marrow proliferation or maturation is must
  • Higher values occur in conditions of acute blood loss, hemolysis, EPO, iron/B12 repletion, etc., Lower values are seen in conditions such as bone marrow ablative disorders, lack of substrate (iron/B12), low EPO, and conditions that impair erythropoiesis.

Red blood cell indices[16]

Marked alteration in these reflect disorders of maturation or IDA. MCV is used to classify anemia as micro-, normo-, and macrocytic anemia.

Normal MCV is the most common finding in anemic men and postmenopausal women.

Low MCHC (hypochromia) reflects a defect in Hb synthesis, whereas higher values are seen spherocytosis or RBC agglutination.

RDW measures the degree of variation among size of RBCs. Higher (>14.5%) values suggest greater variation in size as seen in IDA, cobalamin deficiency, folate deficiency, myelodysplastic syndrome, hemoglobinopathies, and postblood transfusion.[17]

Peripheral blood smear is used to look at the morphology of the various types of cells or presence of any abnormal cells[18],[19]

  • Anisocytosis correlates with increase in RDW or range of cell sizes
  • Poikilocytosis suggests defect in maturation of red cell precursors in bone marrow or fragmentation of circulating red cells
  • Polychromasia is seen when reticulocytes (prematurely released from BM)-appear in circulation in response to EPO stimulation or architectural damage of BM (fibrosis, malignant infiltration, etc.)
  • Howell–Jolly bodies – Absence of functional spleen
  • Bite cells/blister cell – G6PD deficiency/oxidant injury
  • Dacryocyte (teardrop) cell – Myelofibrosis
  • Target cells – Cholestasis, HbC disease, thalassemia (target, teardrop, hypochromic, microcytic, and bizarre-shaped cells), IDA, liver disease
  • Spherocytes/elliptocytes/stomatocytes – hereditary spherocytosis/elliptocytosis/stomatocytosis
  • Sickle cells – sickle cell disease
  • Schistocytes/fragmented red cells – Microangipathic hemolytic conditions and mechanical hemolytic anemia (e.g. disseminated intravascular coagulation, thrombotic thrombocytopenic purpura – hemolytic uremic syndrome HELLP syndrome, valvular heart disease (e.g. AS), prosthetic heart valves, and thermal injury),
  • Burr cells/echinocytes – uremia (renal failure), malnutrition
  • Spur cells/acanthocytes – Spur cell anemia and abetalipoproteinemia
  • Basophilic stippling – Lead poisoning and sideroblastic anemia.

Bone marrow examination[20]

It is indicated in conditions like:

  • Hypoproliferative anemia with a normal iron status
  • Severe pancytopenia; pancytopenia with hemolysis or thrombosis; pancytopenia or bicytopenia in older individuals with normal B12, folate, and Cu levels
  • Abnormal cells such as blasts, immature myeloid, immature lymphoid forms, hairy cells, LGL, and prolymphocytes seen in peripheral blood
  • Leukoerythroblastosis ± dacrocytes.

Hypoproliferative anemia and RPI <2 (no erythroid hyperplasia) → M/E ratio is 2–3:1

Hemolytic disease and RPI >3 (indices normocytic to slightly macrocytic) → M/E ratio is at least 1:1

Discrepancy between M/E ratio and RPI (Erythroid hyperplasia; M/E ratio <1:1; low or slight elevated RPI indicating destruction within marrow of developing erythroblasts) seen in maturation disorders or Ineffective erythropoiesis

Ring Sideroblasts can be seen in MDS.

Caution: Blood transfusion and administration of hematinics can affect the BM picture as well as serum iron, B12, and folate levels. So if possible, these investigations should be done before transfusing or starting hematinics.

Iron studies

  • Serum iron alone is not a reliable indicator of iron stores as it can be increased acutely by recent transfusion
  • Serum iron and hence transferrin saturation show diurnal variation
  • Serum ferritin is an acute-phase reactant, hence can be falsely high in inflammatory states. Despite this, values >200 μg/L mean at least some iron in tissue stores is present, whereas values of 10–15 μg/L indicate depletion.

Hemoglobin electrophoresis[21]

To be done in:

  • Microcytic anemia (if no IDA or ACD/AI)
  • Unexplained hemolytic anemia
  • Abnormal-shaped RBCs in peripheral blood smear
  • Family history of hemoglobinopathy
  • Positive neonatal screen results
  • Positive sickle cell or solubility test.

Normal values observed commonly are hbA1: 95%–98%; hbA2: 2%–3%; hbF: 0.8%–2%; and hbS/C/E: 0%

Direct or indirect antiglobulin test[1]

Distinguishes immune (DAT+) from nonimmune (DAT−) causes. DAT positivity may occur after transfusion sometimes.

[TAG:2]HbA1c and Anemia[22][/TAG:2]

Exposure of erythrocytes for longer or shorter duration to the effect of hyperglycemia like

  • Prolonged lifespan of erythrocytes or

Reduced rate of their regeneration, for example, iron/B12/folic acid deficiency anemia and functional asplenia Lead to falsely higher HbA1c levels

  • Shortened lifespan of erythrocytes or

Increased rate of regeneration, for example, blood loss/hemolysis, splenomegaly, and pregnancy lead to falsely lower HbA1C levels

In other causes such as homozygous hemoglobinopathy, hereditary persistence of fetal Hb and ESRD methods other than HbA1c, such as fructosamine level measurement and glycosylated albumin levels, should be used.

  Clinical Pearls Top

  • Always send blood films in patients with an unclear etiology of anemia
  • Consider screening for sickle cell thalassemia in patients with unexplained anemia or with family history of these conditions
  • Patients often have nonspecific symptoms with anemia and a careful history and physical examination are needed
  • In the adult population, evaluating the gastrointestinal system as a potential cause of iron-deficient anemia can be a diagnostic challenge
  • Anemia is more common with advanced age, but not normal and should be worked up!

  Classification of Anemia Top

After history, examination, and basic laboratory investigations, questions that need to have been answered are:

Q. Is the patient actively bleeding? And if so cause, site and quantity of bleed?

(Most common nontraumatic causes of hemorrhage include gastrointestinal, gynecologic, and genitourinary)

Q. What category does the anemia fall into on the basis of cell size, Hb density, and cell morphology?

Q. Is the patient's bone marrow actively producing RBCs to compensate for anemia?

(Reticulocyte count or percentage with appropriate corrections are somewhat nonspecific but best peripheral estimate available)

Q. Is hemolysis present?

(LDH, haptoglobin and indirect bilirubin are individually nonspecific but in conjunction may suggest hemolysis)

With the above questions in mind, anemia must be classified to narrow down the potential etiology and subsequent management.

[TAG:2]Various Causes According to Functional Classification of Anemia[5],[23][/TAG:2]

Anemia can be classified physiologically as anemia due to marrow production defect, maturation defect and decreased survival [Figure 1].
Figure 1: Algorithm for physiologically classifying Anemia[5]

Click here to view

Hypoproliferation (marrow production defects) – 75% of all cases of anemia

  1. Marrow damage

    1. Infiltration/fibrosis
    2. Aplasia

  2. Mild-moderate IDA (marrow proliferation is blunted)
  3. Inadequate stimulation

    • Inflammation (IL-1 suppresses EPO production)
    • Metabolic defect (Hypothyroidism – decreased tissue O2 need)
    • Renal disease

Ineffective erythropoiesis (maturation defects)

  1. Nuclear maturation defects (macrocytosis)

    • Folate deficiency
    • Vit B12 deficiency
    • Drug toxicity (methotrexate, alkylating agents, and alcohol)
    • Myelodysplasia

  2. Cytoplasmic maturation defects (microcytosis and hypochromia)

    • IDA (severe and prolonged anemia-hyperplastic marrow)
    • Thalassemia
    • Sideroblastic anemia

Blood loss/hemolysis (decreased survival)

  1. Blood loss
  2. Intravascular hemolysis
  3. Metabolic defect

    • Deficiency of enzymes: G6PD, pyruvate kinase, glucose-phosphate isomerase, 5' nucleotidase
    • Heavy metal excess (Wilson's disease, Copper toxicity, Arsine toxicity)
    • Hypophosphatemia

  4. Membrane abnormality

    • Composition abnormality: Hereditary spherocytosis/elliptocytosis
    • Hydration abnormality: Hereditary stomatocytosis/xerocytosis
    • Liver disease

  5. Hemoglobinopathy

    • Sickle cell disease
    • Thalassemia
    • HbC, HbE, and unstable Hb variants

  6. Immune destruction

    • Warm autoimmune hemolytic anemia
    • Drug-induced immune hemolysis
    • Transfusion reactions (e.g., ABO incompatibility, alloantibodies)
    • Paroxysmal cold hemoglobinuria
    • Paroxysmal nocturnal hemoglobinuria
    • Cold agglutinin disease
    • Intravenous infusion of IVIG or anti-RhD immune globulin

  7. Fragmentation hemolysis

    • Microangiopathic hemolytic anemia
    • Mechanical (intravascular devices, artificial heart valve, giant hemangioma, and foot strike hemolysis).


  • If both BM suppression and blood loss/hemolysis is there, reticulocyte count will be inappropriately low
  • Acute blood loss/very recent bleeding will not be associated with an increased RPI due to inadequate time for EPO and marrow response[5]
  • Subacute blood loss leads to modest reticulocytosis, whereas chronic blood loss presents often like IDA[5]
  • Chronic hemolysis states have stable Hb, high reticulocyte count, normal LDH, and normal bilirubin levels[17]
  • Intramedullary hemolysis due to ineffective erythropoiesis leads to elevated bilirubin and LDH without reticulocytosis[17]
  • In recovering state, there is increase in Hb, decrease in RPI and underestimation of HbA1C.[22]

  Classification and Causes OF Anemia On The Basis Of Morphology Of Red Blood Cells Top

Anemia can be classified on the basis of RBC morphology as microcytic, normocytic and macrocytic [Figure 2].
Figure 2: Classification of anemia on the basis of RBC morphology

Click here to view

Mean cell volume <80 fL (Microcytosis)[17]

  1. IDA
  2. Decreased globin chains (thalassemia, HbC, and HbE)
  3. Decreased heme (sideroblastic anemia and lead poisoning)
  4. ACD/AI.

IDA can also lower HbA2 level (making diagnosis of thalassemia more confusing).[24]

Iron profile, STfR, Hb electrophoresis, and tests for coexisting chronic conditions would help to further delineate the cause. If iron studies show a low ferritin level (<20–30 ng/mL) or transferrin saturation (<19%), it would point toward IDA; if not, it could be thalassemia or ACD/AI. Ferritin concentration is the gold standard test for the diagnosis of IDA. IDA is likely when using a cutoff <41 ng/mL and <15 ng/mL is diagnostic of IDA.

Ferritin is an acute-phase reactant which would be raised in inflammatory conditions.

IDA can also be differentiated from thalassemia trait using Mentzer index which is the ratio of MCV (fL)/RBC count (millions/μl). Value <13 makes thalassemia more likely.[25]

Soluble transferrin receptor (sTfR), a truncated fragment of the membrane receptor, is inversely related to iron levels in blood. It is not sensitive to inflammation. Hence, high sTfR level indicates iron deficiency even if ferritin is elevated. Helping in differentiating IDA from ACD/AI coexisting with IDA [Table 3].[26]
Table 3: Iron deficiency versus anemia of chronic disease/anemia of inflammation versus both the conditions together[26],[27]

Click here to view

Mean cell volume 80–100 fL (Normocytic)[17]

Most difficult differential

  1. Early stages of iron, Vitamin B12, folate, and copper deficiency
  2. Combined microcytic and macrocytic anemia (dimorphic anemia)
  3. ACD/AI (Commonly associated conditions)
  4. Malignancy (hematological and solid tumor) and myelodysplastic syndromes
  5. CKD
  6. Rheumatological conditions (RA, SLE, vasculitis, sarcoidosis, etc.)
  7. Aplastic anemias and clonal cytopenias of uncertain significance
  8. Infections
  9. DM
  10. Anemia of heart failure
  11. Endocrine disorders – hypothyroidism, androgen deficiency, adrenal insufficiency (caveat: may be masked by volume contraction)
  12. Early blood loss
  13. Hemolysis without mark reticulocytosis
  14. Partially treated anemia/following transfusion
  15. Pure red cell aplasia
  16. Drug-induced
  17. Liver disease or alcohol use.

[TAG:2]Anemia of Chronic Disease/Anemia of Inflammation[23],[26],[27][/TAG:2]

It's said to be the second most common cause of anemia after IDA. It is caused by wide-ranging conditions (some of which have been listed above). The common underlying pathophysiology includes dysregulation of iron homeostasis (hallmark), impaired proliferation of erythroid progenitor cell and blunted erythropoietin response.

Microorganisms (lipopolysaccharide-LPS), malignant cells, and autoimmune dysfunction via their immune effector mechanisms activate CD3 + T cells and monocytes which leads to increased production of IFN-γ, TNF-α, IL-1, IL-6, IL-10, etc.

The effects of these include: IL-6 and LPS stimulate hepatic expression of hepcidin (it is an acute phase reactant leading to downregulation of ferroportin which prevents the release of Fe2+ from reticuloendothelial system, hepatocytes, and enterocytes into circulation); increased expression of divalent metal transporter 1 (DMT-1) on macrophages leading to increased uptake of Fe2+; increased degradation of senescent erythrocytes by macrophages; upregulation of transferrin receptor (by anti-inflammatory cytokine IL-10) leading to increased uptake of transferrin bound iron into macrophages; induction of ferritin expression promoting storage of iron within macrophages; inhibition (IFN-γ most potent inhibitor) of proliferation and differentiation of erythroid precursors (burst forming units and colony-forming units), and direct toxic effects on progenitor cells.

These lead to decreased iron availability in circulation for erythropoiesis, increased storage form of iron in cells of RES, decreased production/activity of erythropoietin, and impaired bone marrow response to anemia.


  • Mild-moderate anemia
  • Red cells are typically normocytic normochromic though moderate degree of microcytosis (due to iron-restricted microcytosis) can also be seen.
  • Iron status: (mentioned earlier).

Chronic kidney disease[28]


Considerable overlap with the pathophysiology of ACD, some factors specific or predominant in CKD include:

Decreased renal erythropoietin synthesis, uremic milieu (polyamines/inflammatory cytokines/elevated PTH) impairing erythropoiesis, decreased RBC half-life,

Absolute or functional iron/B12/folate deficiency, chronic immune activation due to contact of immune cells with dialysis membrane, and decreased testosterone levels.[29]


hypoproliferative, normocytic (usually), and normochromic:

  • Low erythropoietic activity consistent with insufficient erythropoietin stimulation characterizes it, but EPO measurements are not routinely indicated
  • Abnormalities of WBC count (total and differential) and platelet counts are not routine
  • RC may be high (if blood loss/hemolysis) or low (hypoproliferative picture)
  • Serum ferritin <=30 ng/mL indicates severe IDA (highly predictive), but values above it do not necessarily mean adequate iron stores due to subclinical inflammation.
  • Levels ≥300 ng/mL indicates normal bone marrow iron stores.
  • Measurement of hepcidin levels are not useful
  • High-sensitivity C-reactive protein-occult inflammation

Rule out other causes

Obtain iron studies, sTfR, RC, LFT, KFT, TFT etc to reach to the probable cause of anemia.

Consider checking EPO levels (if low, then patient might respond to an erythropoietin stimulating agent)

Mean cell volume >100 fL (Macrocytosis)[17]

  1. Abnormalities of DNA metabolism

    • Vitamin B12 deficiency
    • Folate deficiency (Decreased intake, impaired absorption, increased requirements and inborn errors)
    • Drugs

      • Antiretroviral therapies for HIV
      • Azathioprine
      • Capecitabine
      • Cladribine
      • Cytosine arabinoside
      • Hydroxyurea
      • Imatinib
      • Methotrexate
      • Metformin
      • Proton Pump Inhibitors

  2. Shift to immature or stressed red cells

    • High reticulocyte count/reticulocytosis (hemolysis, recovery from bleeding, removal of a bone marrow insult, repletion of deficient nutrients)
    • Action of erythropoietin – Skip macrocytes and stress erythrocytosis
    • Aplastic anemia/Fanconi anemia
    • Pure red cell aplasia

  3. Primary Bone marrow disorders

    • Myelodysplastic syndromes
    • Congenital dyserythropoietic anemias
    • Some sideroblastic anemias
    • Large granular lymphocyte (LGL) leukemia

  4. Lipid abnormalities

    • Liver disease
    • Hypothyroidism

  5. Spurious

    • Increased Ig or acute phase proteins cause rouleaux formation (mistakenly counted as a large cell)

  6. Unknown mechanism

    • Alcohol abuse
    • Multiple myeloma/plasma cell disorders.


Obtain RC, LFT, KFT, TFT, B12/folic acid level, methylmalonic acid level etc to reach to the probable cause of anemia.

If there is no answer, then go ahead with bone marrow studies.

If serum B12 level is higher than the normal in a patient not on supplementation,

consider myeloproliferative neoplasm (associated with increased production of transcobalamin, the Vitamin B12 binding protein).

Myelodysplastic syndrome is a likely differential to be considered if unexplained macrocytic anemia is observed.

[TAG:2]Dimorphic Anemia[30][/TAG:2]

It is a commonly encountered entity in clinical practice and particularly in the Indian subcontinent, it refers to combined microcytic anemia (IDA >> thalassemia minor, ACD) and megaloblastic anemia (Vitamin B12/folic acid/copper deficiency) in a patient.

Clinical scenarios where its commonly seen include, pregnancy, hookworm anemia with nutritional deficiency, celiac disease, Helicobacter pylori infection, and gastric reduction surgery.


Anemia is normocytic or even microcytic, MCV is in the normal range and RDW is increased.

Iron studies show an IDA anemia picture with B12/folic acid/copper levels also decreased (depending on the macrocytic component). The normal MCV may be misleading; hence, peripheral blood film examination which would show both microcytes and macroovalocytes would help reach a diagnosis. Hypersegmented neutrophils may be also seen. Bone marrow would show intermediate megaloblasts that are smaller and look less megaloblastic than usual, giant metamyelocytes, and band forms. Neutrophil myeloperoxidase levels would be high.

History, clinical examination, and part response to therapy with megaloblastic features becoming more prominent if only treated with iron supplementation are other clues to the diagnosis.

  Conclusion Top

Reaching a specific diagnosis irrevocably would require a wide variety of investigations. But with an above approach focusing on complaints, past history, examination, and few laboratory tests would enable us to reach to the probable cause of anemia in a majority of cases. Some commonly encountered conditions, confusion, and caveats which are encountered while approaching a case of anemia have also been addressed.

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Conflicts of interest

There are no conflicts of interest.

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  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3]


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