Pediatric emergency medicine trisk 303

FIGURE 62.1 The diagnostic approach to pallor. CBC, complete blood cell; WBC, white blood
cell; PLT, platelet; RBC, red blood cell; MCV, mean corpuscular volume; G6PD, glucose-6phosphate dehydrogenase; DIC, disseminated intravascular coagulation; TEC, transient
erythroblastopenia of childhood; HbSS, sickle cell anemia.

Numerous classifications of anemia have been used to assist the physician in
the laboratory investigation of pallor. Historically, the reticulocyte count and the
MCV have been helpful measurements in categorizing causes of anemia. The
reticulocyte count can be performed rapidly and, as shown in Figure 62.1 , helps
distinguish anemias caused by impaired red cell production (e.g., iron deficiency,
hypoplastic anemia) from those caused by shortened red cell survival (e.g.,
hemoglobinopathies, membrane disorders, and other hemolytic states). The MCV
provides a quick, accurate, and readily available method of distinguishing the
microcytic anemias (iron deficiency, thalassemia syndromes) from the
normocytic (membrane disorders, enzyme deficiencies, autoimmune hemolytic
anemia, most hemoglobinopathies) or macrocytic (bone marrow/stem cell failure,
disorders of B12 and folic acid absorption or metabolism) anemias.
The reticulocyte count and MCV should be interpreted with caution. As shown
in Figure 62.1 , disorders of shortened red cell survival are not always
characterized by an increased reticulocyte count. For example, reticulocytopenia
may occur in autoimmune hemolytic anemia, despite active hemolysis and


increased erythropoiesis in the bone marrow. Chronic hemolytic disorders, such
as sickle cell anemia or hereditary spherocytosis, may first be detected during an
aplastic crisis when the reticulocyte count is low. Unless the underlying disorder
is recognized, the physician may be misled by this finding. Furthermore, because
the reticulocyte count is expressed as a percentage of total red cells, it must be
indexed for the degree of anemia. The easiest way to calculate the reticulocyte
index is to multiply the reticulocyte count by the reported hemoglobin or
hematocrit (HCT pt [patient]) divided by normal hemoglobin or hematocrit (HCT
nl [normal]):

For example, a reticulocyte count of 5% in a child with severe iron-deficiency
anemia and a hematocrit of 6% are not elevated when corrected for the degree of
anemia (5% × 6%/33% = 0.9%). The normal reticulocyte index is between 1.0
and 2.0.
The MCV varies with age, necessitating the use of age-adjusted normal values
( Table 62.4 ). In addition, the measured MCV represents an average value. If
microcytic and macrocytic red cells are present in the peripheral blood as, for
example, in a patient with combined iron deficiency and B12 deficiency, the MCV
may remain normal. Therefore, the peripheral smear should be examined
carefully to determine whether the MCV reflects a single population of red cells
of uniform size, or two or more populations of distinctly different size. The red
cell distribution width (RDW) is elevated in the presence of increased variation in
red cell size.
As shown in Figure 62.1 , the reticulocyte count and MCV help in the initial
classification of anemia but leave the physician with broad categories of disease,
rather than specific diagnoses. In many instances, the history and physical
examination, when coupled with these laboratory measurements, permit
identification of a particular disorder. When this is not possible, consultation with
a hematologist, additional laboratory studies, and careful examination of the
peripheral smear may be required to characterize the disease.


TABLE 62.4
AGE-RELATED VALUES FOR MEAN CORPUSCULAR VOLUME
MCV (fL)
Age (yrs)
0.5–2
2–5
5–9

9–12
12–14:
Female
Male
14–18:
Female
Male

Median

Lower limit a

77
79
81
83

70
73
75
76

85
84

77
76

87
86

78
77

a Third

percentile.
fL, femtoliters.

SUMMARY
Pallor can be a sign of severe illness and indicate the need for rapid assessment
and emergent stabilization. Once this has been initiated, a systematic approach to
determine the etiology of pallor should be undertaken. Combining elements of the
history, physical examination, and laboratory data will assist the clinician in
identifying whether the anemia is caused by decreased production, increased
destruction, or blood loss. As a result, an effective management strategy can be
developed.
Suggested Readings and Key References
Burns RA, Woodward GA. Transient erythroblastopenia of childhood: a review
for the pediatric emergency medicine physician. Pediatr Emerg Care
2019;35(3):237–240.
Chalco JP, Huicho L, Alamo C, et al. Accuracy of clinical pallor in the diagnosis
of anaemia in children: a meta-analysis. BMC Pediatr 2005;5:46.


Grace RF, Glader B. Red blood cell enzyme disorders. Pediatr Clin North Am
2018;65(3):579–595.
Orkin SH, Fisher DE, Look AT, et al., eds. Nathan and Oski’s Hematology of
Infancy and Childhood . 8th ed. Philadelphia, PA: WB Saunders; 2015.
Subramaniam S, Chao JH. Managing acute complications of sickle cell disease in

pediatric patients. Pediatr Emerg Med Pract 2016;13(11):1–28.