Classification and diagnosis of anemia in children and neonates

Classification and diagnosis

Anemia is defined as a reduction in hemoglobin concentration, hematocrit, or red cell mass by more than two standard deviations below the mean for age and sex for the normal population. The normal ranges are also affected by geographic ancestry; African Americans have lower hemoglobin concentration on average (by ~0.5 g/dL) than people of European ancestry. As a result, 2.5% of the general population and up to 10% of African Americans will be classified as anemic, especially if race-specific normal ranges are not used. Also note that children with cyanotic congenital heart disease, chronic respiratory insufficiency, arteriovenous pulmonary shunts, or hemoglobinopathies that alter oxygen affinity can be functionally anemic with hemoglobin levels in the normal or reference range.

• Anemia can be an isolated abnormality or be a part of multiple cell line abnormalities (red cells, white cells, and platelets). Abnormalities of two- or three-cell lines may indicate one of the following:

  • bone marrow involvement (e.g., infections, aplastic anemia, leukemia, toxicity from medications);

  • autoimmune disorders (e.g., connective tissue disease, Evans syndrome);

  • sequestration (e.g., hypersplenism) or intravascular trapping and destruction (e.g., thrombotic microangiopathy).

• Anemia can be classified based on morphology (e.g., size and shape of RBCs) or physiology (i.e., mechanism of anemia). Physiologically, anemia can be categorized into:

  • disorders of decreased red cell formation: this can be due to failure of erythropoiesis in which there is an absolute erythroblastopenia and reticulocytopenia (e.g., marrow failure diseases) or due to ineffective erythropoiesis in which the marrow has many erythroblasts but with defective maturation (e.g., thalassemias);

  • disorders of erythrocyte destruction (hemolysis);

  • loss of red blood cells (hemorrhage).

Table 3.1 presents an etiologic classification of anemia and the diagnostic features.

• The blood smear is an essential first step in the diagnosis of anemia. Anemia can be classified based on RBC morphology and RBC size into microcytic [decreased mean corpuscular volume (MCV)], normocytic (normal MCV), and macrocytic (high MCV). The mean corpuscular hemoglobin (MCH) and MCH concentration (MCHC) are calculated values and have complementary diagnostic value. The MCH usually parallels the MCV. The MCHC is a measure of cellular hydration status. A high value (>35 g/dL) due to membrane loss is characteristic of spherocytosis, and a low value is commonly associated with iron deficiency. Fig. 3.1 delineates the causes of anemia based on peripheral blood morphology, and Table 3.2 shows the cause of anemia based on MCV and red cell distribution width (RDW), an index of the variation in red cell size (anisocytosis).

  
  Table 3.2

  Classification of nature of the anemia based on mean corpuscular volume (MCV) and red cell distribution width (RDW).

  From Lanzkowsky, P., 2016. Lanzkowsky’s Manual of Pediatric Hematology and Oncology, sixth ed. Elsevier.

  	MCV low	MCV normal	MCV high
  RDW normal	Microcytic homogeneous	Normocytic homogeneous	Macrocytic homogeneous
  	Heterozygous thalassemia	Normal	Inherited bone marrow failure syndromes
  	Chronic disease	Chronic disease	"Preleukemia" or myelodysplastic syndrome
  		Chronic liver disease
  		Chemotherapy
  		Chronic myelocytic leukemia
  		Hemorrhage
  		Hereditary spherocytosis
  RDW high	Microcytic heterogeneous	Normocytic heterogeneous	Macrocytic heterogeneous
  	Iron deficiency	Early iron or folate deficiency	Folate deficiency
  	HbS/β-thalassemia	Mixed deficiencies	Vitamin B 12 deficiency
  	Hemoglobin H	Hemoglobinopathy (e.g., Hb SS)	Immune hemolytic anemia
  	Red cell Fragmentation disorders	MyelofibrosisSideroblastic anemia	Cold agglutinins

  Abbreviations: Hb , hemoglobin; HbS/β-thalassemia , sickle-beta-thalassemia; Hb SS , homozgous sickle cell anemia.

• In addition, the blood smear may show specific morphologic abnormalities suggestive of red cell membrane disorders (e.g., spherocytosis, stomatocytosis, or elliptocytosis) or hemoglobinopathies (e.g., sickle cell disease and thalassemia). Table 3.3 lists the differential diagnosis of anemia based on the specific red cell morphological abnormalities.

  Table 3.3

  Specific red cell morphologic abnormalities.

  From Lanzkowsky, P., 2016. Lanzkowsky’s Manual of Pediatric Hematology and Oncology, sixth ed. Elsevier.

  Target cells— Increased surface/volume ratio (generally does not affect red cell survival) 1. Thalassemic syndromes 2. Hemoglobinopathies a. Hb C trait or Hb C disease b. Sickle cell disease c. Hb E trait or Hb E disease d. Hb D trait 3. Liver disease 4. Postsplenectomy or hyposplenic states 5. Severe iron deficiency 6. LCAT deficiency: congenital disorder of lecithin/cholesterol acyltransferase deficiency (corneal opacifications, proteinuria, target cells, moderately severe anemia) 7. Abetalipoproteinemia Spherocytes— Decreased surface/volume ratio, hyperdense (>MCHC) 1. Hereditary spherocytosis 2. ABO incompatibility: antibody-coated fragment of RBC membrane removed 3. Autoimmune hemolytic anemia: antibody-coated fragment of RBC membrane removed 4. G6PD deficiency 5. MAHA: fragment of RBC lost after impact with abnormal surface 6. Sickle cell disease: fragment of RBC removed in reticuloendothelial system 7. Hypersplenism 8. Burns: fragment of damaged RBC removed by spleen 9. Posttransfusion 10. Pyruvate kinase deficiency Acanthocytes (spur cells)— Cells with 5–10 spicules of varying length; spicules irregular in space and thickness, with wide bases; appear smaller than normal cells because they assume a spheroid shape 1. Liver disease 2. Disseminated intravascular coagulation (and other MAHA) 3. Postsplenectomy or hyposplenic state 4. Vitamin E deficiency 5. Hypothyroidism 6. Abetalipoproteinemia: rare congenital disorder; 50–100% of cells acanthocytes; associated abnormalities (fat malabsorption, retinitis pigmentosa, neurologic abnormalities) 7. Malabsorptive states Echinocytes (burr cells)— 10–30 spicules equal in size and evenly distributed over RBC surface; caused by alteration in extracellular or intracellular environment 1. Artifact 2. Renal failure 3. Dehydration 4. Liver disease 5. Pyruvate kinase deficiency 6. Peptic ulcer disease or gastric carcinoma 7. Immediately after red cell transfusion 8. Rare congenital anemias due to decreased intracellular potassium

  Pyknocytes— Distorted, hyperchromic, contracted RBC; can be similar to echinocytes and acanthocytes

  Schistocytes— Helmet, triangular shapes, or small fragments. Caused by fragmentation upon impact with abnormal vascular surface (e.g., fibrin strand, vasculitis, artificial surface in circulation) 1. DIC; 2. severe hemolytic anemia (e.g., G6PD deficiency); 3. MAHA 4. hemolytic uremic syndrome; 5. prosthetic cardiac valve, abnormal cardiac valve, cardiac patch, coarctation of the aorta; 6. connective tissue disorder (e.g., SLE); 7. Kasabach–Merritt syndrome; 8. purpura fulminans; 9. renal vein thrombosis; 10. burns (spheroschistocytes as a result of heat); 11. thrombotic thrombocytopenia purpura; 12. homograft rejection; 13. uremia, acute tubular necrosis, glomerulonephritis; 14. malignant hypertension; 15. systemic amyloidosis; 16. liver cirrhosis; and 17. disseminated carcinomatosis. Elliptocytes— Elliptical cells, normochromic; seen normally in less than 1% of RBCs; larger numbers occasionally seen in a normal patient 1. hereditary elliptocytosis; 2. iron deficiency (increased with severity, hypochromic); 3. sickle cell disease; 4. thalassemia major; 5. severe bacterial infection; 6. sickle cell trait; 7. leukoerythroblastic reaction; 8. megaloblastic anemias; 9. any anemia may occasionally present with up to 10% elliptocytes; and 10. malaria. Teardrop cells— Shape of drop, usually microcytic, often also hypochromic 1. Newborn 2. Thalassemia major 3. Leukoerythroblastic reaction 4. Myeloproliferative syndromes 5. Bone marrow infiltration Stomatocytes— Has a slit-like area of central pallor 1. Normal (in small numbers) 2. Hereditary stomatocytosis/xerocytosis 3. Artifact 4. Thalassemia 5. Acute alcoholism 6. Rh null disease (absence of Rh complex) 7. Liver disease 8. Malignancies Nucleated red blood cells— Not normal in the peripheral blood beyond the first week of life 1. Newborn (first 3–4 days) 2. Intense bone marrow stimulation a. Hypoxia (especially postcardiac arrest) b. Acute bleeding c. Severe hemolytic anemia (e.g., thalassemia, sickle cell disease) 3. Congenital infections (e.g., sepsis, congenital syphilis, CMV, rubella) 4. Postsplenectomy or hyposplenic states: spleen normally removes nucleated RBC 5. Leukoerythroblastic reaction: seen with extramedullary hematopoiesis and bone marrow replacement; most commonly leukemia or solid tumor—fungal and mycobacterial infection may also do this; leukoerythroblastic reaction is also associated with teardrop red cells, 10,000–20,000 WBC with small-to-moderate numbers of metamyelocytes, myelocytes, and promyelocytes; thrombocytosis with large bizarre platelets 6. Megaloblastic anemia 7. Dyserythropoietic anemias Blister cells —Red cell area under membrane free of hemoglobin, appearing like a blister 1. G6PD deficiency or unstable hemoglobinopathy (during hemolytic episode) 2. Sickle cell disease (rare) 3. Pulmonary emboli (rare) Basophilic stippling— Coarse or fine punctate basophilic inclusions that represent aggregates of ribosomal RNA 1. Hemolytic anemias 2. Iron deficiency anemia 3. Lead poisoning Howell–Jolly bodies— Small, well-defined, round, densely stained nuclear-remnant inclusions; 1 mm in diameter; centric in location 1. Postsplenectomy or hyposplenia 2. Newborn 3. Megaloblastic anemias 4. Dyserythropoietic anemias 5. A variety of types of anemias (rarely iron-deficiency anemia, hereditary spherocytosis) Cabot’s ring bodies— Nuclear-remnant ring configuration inclusions 1. Pernicious anemia 2. Lead toxicity Heinz bodies— Denatured aggregated hemoglobin 1. Normal in newborn 2. Thalassemia 3. Asplenia 4. Chronic liver disease 5. Heinz body hemolytic anemia

  Abbreviations: CMV , cytomegalovirus; Hb , hemoglobin; SLE , systemic lupus erythematosus.

• The reticulocyte count is an important indicator of the physiology of anemia ( Fig. 3.2 ). An elevated reticulocyte count suggests blood loss or hemolysis, while a normal or decreased count suggests impaired red cell formation. With acute blood loss or sequestration, the elevation of the reticulocyte count may take many hours to become apparent and several days (4–5) to reach its maximum. The reticulocyte count must be interpreted in the context of the degree of anemia, using either the absolute reticulocyte count or reticulocyte index, to assess the adequacy of erythropoiesis. In patients with bleeding or hemolysis, the reticulocyte index should be at least 3%, whereas in patients with anemia due to decreased production of red cells, the reticulocyte index is <3% and frequently <1.5%.

  

Table 3.4 lists various laboratory studies helpful in the investigation of a patient with anemia.

• The investigation of anemia entails the following steps:

  • Detailed history . Table 3.1 lists the various causes of anemia with the associated diagnostic laboratory and clinical features.

  • Complete blood count to establish whether anemia is isolated or part of a multilineage abnormality (abnormality of red cell count, white blood cell count, and platelet count). Determination of the morphologic characteristics of the anemia based on blood smear ( Fig. 3.1 and Table 3.3 ) and consideration of the MCV ( Fig. 3.2 and Table 3.2 ) and RDW ( Table 3.2 ) and white blood cell and platelet morphology .

  • Reticulocyte count as a reflection of erythropoiesis ( Fig. 3.2 ).

  • Determination of whether there is evidence of a hemolytic process by:

    • –

      consideration of the clinical features suggesting hemolytic disease ( Table 3.5 ),

      Table 3.5

      The clinical features suggestive of hemolysis.

      From Lanzkowsky, P., 2016. Lanzkowsky’s Manual of Pediatric Hematology and Oncology, sixth ed. Elsevier.

      Ethnogeographic factors: high incidence of sickle trait in people of African ancestry, high incidence of thalassemia trait in people of Mediterranean ancestry, and high incidence of G6PD deficiency among Sephardic Jews. Age factors: anemia and jaundice in an Rh-positive infant born to a mother who is Rh negative or a group A or group B infant born to a group O mother (setting for a hemolytic anemia) History of anemia, jaundice, or gallstones in family Persistent or recurrent anemia associated with reticulocytosis Anemia unresponsive to iron or vitamin supplements Intermittent bouts or persistent indirect hyperbilirubinemia Splenomegaly Hemoglobinuria Presence of gallstones Chronic leg ulcers Development of anemia or hemoglobinuria after exposure to certain drugs Dark urine due to dipyrroluria: unstable hemoglobins, thalassemia, and ineffective erythropoiesis

      Abbreviation: G6PD , Glucose-6-phosphate dehydrogenase.

    • –

      laboratory demonstration of the presence of hemolysis ( Table 3.4 ), and

    • –

      determination of the precise cause of the hemolytic anemia by special hematologic investigations ( Table 3.4 ).

  • Bone marrow aspiration and biopsy , if required, to examine erythroid, myeloid, and megakaryocytic morphology to determine whether there is normoblastic, megaloblastic, or sideroblastic erythropoiesis and to exclude marrow pathology (e.g., aplastic anemia, leukemia, and benign or malignant infiltration of the bone marrow) ( Fig. 3.3 ).

    

  • Determination of underlying cause of anemia by additional tests ( Table 3.4 ).

Neonatal anemia

Anemia during the neonatal period can be caused by:

• hemorrhage : acute or chronic;

• hemolysis : congenital hemolytic anemias or due to immune hemolytic anemias; and

• hypoplasia : failure of red cell production in inherited bone marrow failure syndromes, for example, Diamond–Blackfan anemia (pure red cell aplasia) or congenital infections.

Table 3.6 lists the causes of anemia in the newborn.