Pediatric Chronic Anemia Workup

To evaluate anemia, obtain initial laboratory tests, including a complete blood count (CBC), a reticulocyte count, and a review of the peripheral smear. Imaging studies can play a role in the diagnosis of underlying disease, while bone marrow aspiration and biopsy can be used to identify the presence of tumor cells and determine cellular morphology.

Base interpretation of the hemoglobin and hematocrit levels on the reference range for the specific age group. Some laboratories provide only a uniform reference range for the entire pediatric age group and not for specific age groups. Interpret this carefully to avoid misdiagnosis. Hemoglobin and hematocrit levels can be used interchangeably, depending on professional preference and familiarity. Essentially, the hematocrit level is 3 times the hemoglobin value.

Red cell indices are quite informative, particularly mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), and red cell distribution width (RDW).

Note that reference ranges for these parameters also vary with age. Because of this, the author suggests using the MCV cut-off point of 70 plus age in years for patients aged 7 years or younger (eg, MCV < 72 is abnormal for a patient aged 2 y).

A high RDW (eg, ≥19-20) with microcytic picture is most often indicative of iron deficiency anemia in the pediatric population. The RDW is also very high in anemia with reticulocytosis, including sickle cell disease.

Macrocytosis suggests folate/vitamin B-12 deficiency; however, nutritional deficiencies of these vitamins are rare. Diamond-Blackfan anemia, aplastic anemia, and myelodysplastic syndrome often present with macrocytic anemia. Patients with sickle cell anemia who have been on hydroxyurea also show macrocytosis.

Note that in newborns, MCV is physiologically in the range of 120-102. Beyond the immediate newborn period, MCV exceeding 98 is very uncommon in children; if the volume exceeds 98, it usually indicates a serious hematologic problem, such as myelodysplastic syndrome, leukemia, aplastic anemia, Diamond-Blackfan anemia, or metabolic disorder.

In most, but not all cases of HS, the MCHC exceeds the upper limit of the reference range.

Reticulocytes are immature, nonnucleated RBCs. An increase in the reticulocyte count (in particular, the absolute reticulocyte count) indicates active erythropoiesis.

The relative reticulocyte count is useful in determining whether anemia is caused by decreased production, increased destruction, or loss of RBCs. An elevated number of reticulocytes is (eventually) observed in individuals with anemia caused by hemolysis or blood loss; note that the absence of reticulocytosis may simply reflect a lag in the response to the acute onset of anemia.

The term reticulocyte count is often inaccurately used to refer to the percentage of reticulocytes, a value that must be interpreted in light of the degree of anemia. Thus, a finding of 2-3% reticulocytes (vs the reference value of approximately 1%) in a patient in whom the hemoglobin level is only one third to one half of reference range does not indicate a reticulocyte response.

Some clinicians prefer to use either the absolute number of reticulocytes/μL of blood or a reticulocyte percentage that is corrected for the degree of anemia. The corrected reticulocyte count equals (patient hematocrit)/(reference range hematocrit) multiplied by the percentage reticulocyte count.

Examination of the peripheral smear is particularly helpful in normocytic anemia. The red cell morphology itself is quite often diagnostic. The following are examples of abnormal cell morphology in normocytic picture:

• Ghost, bite, or helmet cells (G-6-PD), as depicted in the image belowBlood smear from a black male with glucose-6-phosphate dehydrogenase (G-6-PD) deficiency that resulted in acute hemolysis. Note blister (helmet or bite) cells and very dense spherocytic cells. The blood smear is virtually pathognomic of this disorder.
• Spherocytes (HS, autoimmune hemolytic anemia, ABO hemolytic anemia in newborns), as depicted in the image belowBlood smear of hereditary spherocytosis (HS). Note many spherocytic cells. Not all patients with HS are anemic.
• Target cells (hemoglobin C, liver disease), as depicted in the image belowBlood smear of hemoglobin C trait. Note numerous target cells. Target cells are a characteristic of this hemoglobinopathy. The trait patient has no anemia. Target cells are also seen in patients with iron deficiency anemia, thalassemia, sickle cell disease, and liver disease.
• Sickle-shaped cells (drepanocytes) (sickle cell disease), as depicted in the image belowBlood smear of a patient with homozygous sickle cell disease. Note several sickle cells, a nucleated RBC, and a red cell with Howell-Jolly body (indicated by an arrow), evidence of functional asplenia.
• Schistocytes or fragmented cells (microangiopathic hemolytic anemia), as depicted in the image belowA blood smear showing a few schistocytes. This patient had Kaposi type hemangioendothelioma with periodic microangiopathic hemolysis and disseminated coagulopathy (Kasabach-Merritt phenomenon).
• Stippled RBCs, basophilic stippling (in all conditions with increased reticulocyte count and in lead poisoning and 5' nucleotidase deficiency), as depicted in the image below A blood smear of a patient with beta thalassemia trait. Note red cells pointed by arrows. Multiple bluish dots in the cells are called basophilic stipplings and consist of aggregated ribosomes. They are often present in immature red cells such as reticulocytes.
• Increased polychromasia (reticulocytosis)

Normal RBC morphology does not exclude hemolysis.

Additional laboratory tests that may be indicated in the diagnosis and treatment of patients with acute anemia include the following:

• Bilirubin level, lactate dehydrogenase (LDH) level (hemolytic anemia), and serum haptoglobulin level (decreased or none in chronic hemolytic anemia)
• Direct antiglobulin or Coombs test (autoimmune hemolytic anemia)
• Hemoglobin electrophoresis (hemoglobinopathies)
• Hemoglobin A2 quantitation (β-thalassemia trait, increased above 3.5%)
• Red cell enzyme studies (eg, G-6-PD, pyruvate kinase), osmotic fragility (spherocytosis) (G-6-PD-deficient red cells may show a normal G-6-PD screening result in the presence of reticulocytosis, and therefore, actual enzyme quantitation is strongly recommended; a normal enzyme level in the presence of reticulocytosis indicates a deficiency)
• Iron, total iron-binding capacity, and ferritin levels (iron deficiency anemia); soluble (serum) transferrin receptor (differentiation of iron deficiency anemia [increased] from anemia of chronic disease [normal]); free erythrocyte protoporphyrin (FEP) or zinc erythrocyte protoporphyrin (for partially treated iron-deficiency anemia), increased in the presence of normal serum iron)
• Stool for occult blood (examine at least 3 specimens; in the presence of demonstrated intestinal blood loss, any given stool specimen finding may be negative, which is why multiple specimens are required before one can conclude a negative finding.)
• Folate and vitamin B-12 levels (macrocytic/megaloblastic anemia)
• Blood typing and cross matching to assess possible isoimmune anemia in a neonate and to prepare for transfusion
• Viral antibody titers and viral DNA by PCR assay (eg, Epstein-Barr virus, cytomegalovirus, parvovirus B19)
• Blood urea nitrogen (BUN)/creatinine levels to assess renal function
• Thyroxine (T₄)/thyroid-stimulating hormone (TSH) levels to exclude hypothyroidism

Chest radiography and echocardiography are indicated for suspected congestive heart failure.

Skull films and films of the hands and wrists may show expanded marrow space. Spine radiography may reveal a paraspinal (vertebral) pseudotumor due to marked expansion of the bone marrow (usually in thalassemia major).

In cases of suspected hypersplenism, using ultrasonography or computed tomography (CT) scanning to detect a large spleen is not recommended. If a thorough physical examination does not detect a palpable spleen, hypersplenism is not a likely diagnosis.

Ultrasonography of the gallbladder for the presence of gallstones in patients with chronic hemolytic anemia may be valuable if the patient has recurrent abdominal pain. Abdominal pain due to gallstones in children is not always in the right upper quadrant. The author has received reports of left upper quadrant pain in children with gallstones that subsided after cholecystectomy.

Other imaging studies are indicated to detect underlying pathology, including the following:

• Magnetic resonance imaging (MRI) of bones for suspected osteomyelitis
• Positron emission tomography (PET) scanning for suspected lymphoma (Hodgkin lymphoma and non-Hodgkin lymphoma)
• Endoscopy for GI ulcers, inflammatory bowel disease, celiac disease

Exclude impending high-output congestive heart failure using electrocardiography (ECG).

Specimens from bone marrow aspiration and biopsy are often essential in helping to characterize overall cellularity, the presence or absence of tumor cells, the morphology and maturation of red cell precursors, and the presence or absence of stainable iron.

Bone marrow aspiration and biopsy can be used to rule out leukemia, aplastic anemia, tumor cells in the marrow (such as neuroblastoma), megaloblastosis, marrow dysplasia, and hemophagocytosis. It can also be employed in detection of the absence of 1 cell line due to pure red cell aplasia or parvovirus infection.