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128 Erythrocyte and Thrombocyte Abnormalities

Clinically Relevant Classification Principle for Anemias: Mean Erythrocyte Hemoglobin Content (MCH)

In current diagnostic practice, erythrocyte count and hemoglobin content (grams per 100 ml) in whole blood are determined synchronously. This allows calculation of the hemoglobin content per individual erythrocyte (mean corpuscular hemoglobin, MCH) using the following simple formula (p. 10):

Hb (g/dl) · 10

Ery (106/µl)

The mean cell volume, hematocrit, MCH, and erythrocyte size can be used for various calculations (Table 22; methods p. 10, normal values Table 2, p. 12). Despite this multiplicity of possible measures, however, in routine diagnostic practice the differential diagnosis in cases of low Hb concentration or low erythrocyte counts relies above all on the MCH, and most forms of anemia can safely be classified by reference to the normal data range of 26–32 pg Hb/cell (1.61–1.99 fmol/cell) as normochromic (within the normal range), hypochromic (below the), or hyperchromic (above the norm). The reticulocyte count (p. 11) provides important additional pathophysiological information. Anemias with increased erythrocyte production (hyper-regenerative anemias) suggest a high reticulocyte count, while anemias with diminished erythrocyte production (hyporegenerative anemias) have low reticulocyte counts (Table 22).

It should be noted that hyporegenerative anemias due to iron or vitamin deficiency can rapidly display hyper-regeneration activity after only a short course of treatment with iron or vitamin supplements (up to the desirable “reticulocyte crisis”).

The practical classification of anemia starts with the MCH:

26–32 pg = normochromic

Less than 26 pg = hypochromic

More than 32 pg = hyperchromic

Hypochromic Anemias

Iron Deficiency Anemia

Most anemias are hypochromic. Their usual cause is iron deficiency from various causes (Fig. 44). To distinguish quickly between real iron deficiency and an iron distribution disorder, iron and ferritin levels should be determined.

 

 

 

 

 

Hypochromic Anemias

129

 

 

 

 

 

 

 

 

 

 

 

Insufficient iron absorption:

 

Chronic bleeding and pathological

 

 

Lower than normal acidity, no

 

loss of iron in the following diseases:

 

 

 

 

 

 

 

 

 

acidity, stomach resection,

 

Disorders of the stomach and

 

 

 

 

accelerated passage from

 

 

intestines (positive benzidine

 

 

 

 

stomach to intestines

 

 

test)

 

 

 

Substances that inhibit ab-

 

Diseases of the urethra

 

 

 

 

sorption of iron, such as citric

 

 

(hematuria!)

 

 

 

 

acids and lactic acids, mucus and

 

Diseases of the female repro-

 

 

 

 

similar materials

 

 

ductive cycle (menorrhagia,

 

 

 

Substances that facilitate iron

 

 

metrorrhagia)

 

 

 

 

absorption are missing

 

 

 

 

 

 

 

(e.g. vitamin C)

 

 

 

 

 

 

 

 

 

 

 

 

 

Insufficient iron supplementation:

Iron-deficient diet

In newborns: insufficient iron transfer from the mother during gravidity

Increased iron requirement:

Growth/maturation

Increased production of the new blood cells

Endogenous redistribution:

Tumors, infections, lung hemosiderosis

Physiological iron loss in females:

Menses

Lactation

Pregnancy

Iron deficiency:

Fatigue, koilonychia, infectious angle (angulus infectiosus oris), PlummerVinson syndrome, possibly “iron deficiency fever”

Anemia

Hypochromy, ring-shaped erythrocytes

Light serum, deficient in color components

Serum iron very reduced

Fig. 44 The most important reasons for iron deficiency (according to Begemann)

130 Erythrocyte and Thrombocyte Abnormalities

Table 22 Diagnostic findings and work-up for the most important disorders of the red cell series

Clinical

Hb

MCH

Erythro-

Reti-

Leuko-

Seg-

Lym-

Other cells

Throm-

findings

 

 

cyte mor-

culo-

cytes

mented

pho-

 

bocytes

 

 

 

phology

cytes

 

nuclei

cytes

 

 

 

 

 

 

 

 

(%)

(%)

 

 

Fatigue,

!

!

Ring-shaped

!

n

n

n

-

n/"

pallor

 

 

erythrocytes,

 

 

 

 

 

 

(dysphagia)

 

 

anisocytosis

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Possibly

!

!

Anisocytosis,

!

n/"

n

n

Possibly

n

fever, weight

 

 

poikilocytosis

 

 

 

 

eosinophils

 

loss

 

 

 

 

 

 

 

"

 

 

 

 

 

 

 

 

 

monocytes "

 

 

 

 

 

 

 

 

left shift

 

Diffuse

!

!/n/" All sizes,

!

n/!

n

n

-

n/!

symptoms

 

 

dimorphic

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Acute

!

n

n

n

n

(")

(!)

-

n/!/"

hemorrhage

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Subjaundice

!

n

n or pathol.,

""

n/!

n

n

Possibly nor-

n/!

 

 

 

possibly

 

 

 

 

moblasts

 

 

 

 

spherocytes

 

 

 

 

 

 

Spleen "

!

!

Target cells

"

n

n

n

Possibly nor-

n

 

 

 

 

 

 

 

 

moblasts

 

 

 

 

 

 

 

 

 

 

 

Paller

!

n

n

!!

!

!

"

Possibly

!!

possibly

 

 

 

 

 

 

 

monocytes"

 

infections

 

 

 

 

 

 

 

 

 

and bleeding

 

 

 

 

 

 

 

 

 

tendency

 

 

 

 

 

 

 

 

 

Pallor

!

"

Macrocytes,

!

!

!

"

Possibly

!/n

possibly

 

 

megalocytes

 

 

 

 

hyperseg-

 

alcohol his-

 

 

 

 

 

 

 

mented

 

tory

 

 

 

 

 

 

 

granulocytes,

 

 

 

 

 

 

 

 

 

possibly nor-

 

 

 

 

 

 

 

 

 

moblasts

 

Plethora,

"

n

n

n

n/"

n

n

-

n/"

possibly

 

 

 

 

 

 

 

 

 

spleen

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Acute bleed-

!

n

n

(")

n

n

n

-

!!

ing tendency

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Diagnostic steps proceed from left to right. The next step is usually unnecessary; :. the next step is optional; #the next step is obligatory. n = normal value, != lower than normal, "= elevated, ( ) = test not relevant, BSG = erythrocyte sedimentation rate.

 

 

 

 

 

 

 

Hypochromic Anemias

131

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BSG

Elec-

Iron

Ferritin

Trans-

 

Tentative

Evidence/

 

Bone marrow

Ref.

 

 

tro-

 

and

ferrin

 

diagnosis

further diag-

 

 

page

 

 

pho-

 

others

 

 

 

nostics

 

 

 

 

 

resis

 

 

 

 

 

 

 

 

 

 

 

 

n

n

!

Ferritin

"

 

Iron deficiency

Determine

 

Erythropoiesis " p. 132

 

 

 

 

!

 

 

anemia

source of bleed-

sideroblasts !,

 

 

 

 

 

 

 

 

 

ing; check iron

 

iron in macro-

 

 

 

 

 

 

 

 

 

absorption

 

phages !

 

 

 

 

 

 

 

 

 

 

 

 

.

 

 

 

"

? α2" !

Ferritin

!

 

Acquired/sec-

Search for

 

Erythropoiesis !,

p. 134

 

γ"

 

n/"

 

 

ondary anemia

trigger

 

sideroblasts !

 

 

 

 

 

 

 

 

(infectious/

 

 

 

 

iron in macro-

 

 

 

 

 

 

 

 

toxic, paraneo-

 

 

 

 

phages"

 

 

 

 

 

 

 

 

plastic)

 

 

 

.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

n

n

"

n/"

!

 

Sideroachrestic

 

 

#

 

Erythropoiesis ",

p. 106

 

 

 

 

 

 

 

 

 

anemia,

 

 

 

 

ring sideroblasts

 

 

 

 

 

 

 

 

myelodysplasia

 

 

 

 

present

 

 

n

n

n/! –

n/"

 

Anemia due to

Search for

 

(Erythropoiesis

p. 140

 

 

 

 

 

 

 

hemorrhaging

source and

 

")

 

 

 

 

 

 

 

 

 

reason for

 

 

 

 

 

 

 

 

 

 

 

hemorrhages

 

 

 

 

n

n

n

Hapto-

(n/!)

 

Hemolytic

Osmotic

 

(Erythropoiesis

p. 140

 

 

 

 

globu-

 

 

anemia

resistance,

 

", right shift)

 

 

 

 

 

lin !!

 

 

 

Coombs test,

 

increased storage

 

 

n

n

n

Hapto-

 

 

Especially:

Hb electro-

 

of iron

 

 

 

 

 

 

p. 138

 

 

 

globu-

 

 

thalassemia

phoresis and

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lin !!

 

 

 

further tests

.

 

 

 

"

n

"/(n)

n/"

(!/n)

 

Aplastic ane-

Search for trig-

 

Hypoplasia of all

p. 146,

 

 

 

 

 

 

 

mia or bone

ger or tumor

 

cell series, or car-

148, 150

 

 

 

 

 

 

 

marrow carci-

 

 

 

 

cinoma cells

 

 

 

 

 

 

 

 

nosia

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

n

n

n/" Vitamin

(!)

 

Megaloblastic

Gastroscopy,

 

Erythropoietic

p. 152

 

 

 

B12

 

 

anemia

determination

 

megaloblasts

 

 

 

 

 

folic acid

 

 

 

of antibodies,

 

 

 

 

 

 

 

!

 

 

 

possibly

 

 

 

 

 

 

 

 

 

 

 

Schilling test

 

 

 

 

n/! n

!

"

"

 

Polyeythemia,

ALP, progress- .

Erythropoiesis " p. 162

 

 

 

 

 

 

 

DD: hypergam-

ion

 

 

 

 

 

 

 

 

 

 

maglobuline-

 

 

 

 

 

 

 

 

 

 

 

 

 

mia

 

 

 

 

 

 

 

n

n

!

duration

 

Thrombocyto-

Search for trig-

 

Elevated mega-

p. 166

 

 

 

 

of

 

 

penic purpura

gers, possibly

 

karyocyte count

 

 

 

 

 

hemor-

 

 

(ITP)

also for anti-

 

 

 

 

 

 

 

rhaging

 

 

 

bodies

 

 

 

 

""

PTT n

132 Erythrocyte and Thrombocyte Abnormalities

Table 23 Normal ranges for physiological iron and its transport proteins

 

Old units

SI units

Serum iron

150–200 µg/dl

27–36 µmol/l

Newborns

Adults

 

 

Female

60–140 µg/dl

11–25 µmol/l

Male

80–150 µg/dl

14–27 µmol/l

TIBC

300–350 µg/dl

54–63 µmol/l

Transferrin

250–450 µg/dl

2.5–4.5g/l

Serum ferritin

 

30–300 µg/l

 

(15–160 µg/l premenopausal)

 

 

 

TIBC = Total iron binding capacity.

This usually renders determination of transferrin and total iron binding capacity (TIBC) unnecessary. If samples are being sent away to a laboratory, it is preferable to send serum produced by low-speed centrifugation, since the erythrocytes in whole blood can become mechanically damaged during shipment and may then release iron. Table 23 shows the variation of serum iron values according to gender and age.

It is important to note that acute blood loss causes normochromic anemia. Only chronic bleeding or earlier serious acute blood loss leads to iron deficiency manifested as hypochromic anemia.

Iron Deficiency and Blood Cell Analysis Focusing on the erythrocyte morphology is the quickest and most efficient way to investigate hypochromic anemia when the serum iron has dropped below normal values. In hypochromic anemia with iron and hemoglobin deficiency (whether due to insufficient iron intake or an increased physiological iron requirement), erythrocyte size and shape does not usually vary much (see Fig. 45). Only in advanced anemias (from approx. 11 g/dl, equivalent to 6.27 mmol/l Hb) are relatively small erythrocytes (microcytes) with reduced MCV and MCH and grayish stained basophilic erythrocytes (polychromatic erythrocytes) seen, indicating inadequate hemoglobin content. Cells with the appearance of relatively large polychromatic erythrocytes are reticulocytes. The details of their morphology can be seen after supravital staining (p. 141). A few target cells (p. 139) will be seen in conditions of severe iron deficiency.

In severe hemoglobin deficiency (! 8 g/dl, equivalent to 4.96 mmol/l) the residual hemoglobin is found mostly at the peripheral edge of the erythrocyte, giving the appearance of a ring-shaped erythrocyte.

Small, hemoglobin-poor erythrocytes indicate iron deficiency

a b

c d

Fig. 45 Iron deficiency anemia. a and b Erythrocyte morphology in iron deficiency anemia: ring-shaped erythrocytes (1), microcytes (2) faintly visible target cells (3), and a lymphocyte (4) for size comparison. Normal-sized erythrocytes (5) after transfusion. c Bone marrow cytology in iron deficiency anemia shows only increased hematopoiesis and left shift to basophilic erythroblasts (1). d Absence of iron deposits after iron staining (Prussian blue reaction). Megakaryocyte (1).

133