Download A Laboratory Approach to the Investigation of Anemia

A LABORATORY APPROACH TO THE INVESTIGATION OF ANEMIA
An Educational Supplement prepared by ALQEP – December 2009
Anemia can be defined as any condition in which the number of red blood cells, the amount of hemoglobin, or
the volume of packed red blood cells in the blood are lower than normal levels.
Clinically this is important when it contributes to decreased oxygen-carrying capacity and decreased oxygen
delivery to tissues. If cardiac, pulmonary or vascular disease is also present, the number of available red cells to
carry oxygen is even more important.
A reduction in red cells or hemoglobin concentration can be broadly thought of as arising in one of three ways:
Decreased production of red cells—such as pure red cell aplasia or aplastic anemia;
Abnormal maturation or function of early erythroid precursors—such as may be seen in
myelodysplastic syndromes;
Increased loss or destruction of red blood cells—through bleeding or hemolysis.
Just as there are many causes of anemia, there are many classification schemes. From a laboratory perspective,
classification according to the size or shape of red cells is common (microcytic vs. macrocytic or spherocytic vs.
non spherocytic). Classification according to cause of anemia such as hemolytic anemia or nutritional anemia is
also possible. Upon first assessment of a new anemia in a patient the most useful classification scheme for
guiding additional diagnostic investigations is to classify according to whether or not polychromasia and/or
reticulocytes are increased. This classification allows us to distinguish between hypoproliferative anemias, where
the bone marrow is not producing adequate numbers of cells and anemias characterized by increased loss or
destruction. The two categories, in turn, lead to two sets of diagnostic investigations, when assessed alongside
the CBC parameters.
The complete blood count provides a large amount of information that also helps to guide the investigation of
anemia. In particular, the MCV, RBC and hemoglobin can be used, along with the presence of reticulocytosis, to
determine which further investigations may be relevant. The HCT, MCH, MCHC and RDW are calculated
values on most analyzers, and are derived from calculations involving the directly measured parameters.
The reticulocyte count is also now available on many automated hematology analyzers. This represents a huge
advance in the accuracy of reticulocyte counting, compared with older, manual methods. Manual reticulocyte
counts are fraught with error owing to technical complexity, small volume dilutions, observer error and variance
of the specific red cell features that identify a reticulocyte. Distribution error is also a concern due to the small
number of cells counted on a manual count. Automated reticulocytes, in contrast, are both accurate and precise
based on literature reports and validation by the Canadian Coalition for Quality in Laboratory Medicine
(CCQLM).
Some examples of the investigation of various types of anemia using these recommendations follow:
© Copyright 2009 College of Physicians and Surgeons of Alberta
A LABORATORY APPROACH TO THE INVESTIGATION OF ANEMIA
Figure 1: Hemolysis Initial Workup
History & Physical
Exam
CBC & Reticulocyte Count
Yes
Reticulocyte count
elevated?
Blood Loss
Hemolysis
Response to Hematinic
therapy
Abnormal Red Cell
Morphology
No
No
Yes
Consider other etiologies
BLEEDING or
response to hematinic
therapy
Hypo / Micro?
See Figure 3
Yes
Assessment for Blood
Loss and/or iron
deficiency or response
to hemotinic therapy
No
No
Other red cell
abnormalities
See Figure 2
Consider:
Haptoglobin
LD
Unconjugated bilirubin
Urine hemosiderin
Plasma free
hemoglobin
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A LABORATORY APPROACH TO THE INVESTIGATION OF ANEMIA
Spherocytes
DAT Positive
No
Specific Morphologic
Changes on Blood Film:
Bite/blister
cells
Oxidative
hemolysis
Stomatocytes
Liver disease
Hereditary
Stomatocytosis
Artifact
Red Cell Inclusions
Target Cells
Basophilic Stippling
Liver disease
Hemoglobinopathy
Splenectomy
Heinz body prep
G6PD
Unstable Hgb
Acanthocytes
Microangiopathic
Hemolytic Anemia
Liver disease
Splenectomy
Abeta lipoproteinemia
Recollect/Reexam
Liver function
tests
Family studies
Hereditary or
acquired (drug
induced) G6PD
deficiency
No Specific Finding
G6PD test
PNH assessment by
flow cytometry
DAT
Heinz body prep
Hemoglobin
electrophoresis /
HPLC
Osmotic fragility /
EMA
Red cell enzyme
screen
Bone marrow studies
Malaria
Note:
DIC – Disseminated intravascular coagulation
EMA - eosin-5'-maleimide binding test
HS – hereditary spherocytosis
HDN – hereditary disease of the newborn
HUS – hemolytic uremic syndrome
PCH – paroxysmal cold hemoglobinuria
TTP – thrombotic thrombocytopenic purpura
Liver disease –
alcoholism
Hereditary
stomatocytosis
Hemoglobin H prep
Hemoglobin
electrophoresis /
HPLC
Abdominal U/S
Unstable Hemoglobin
Hemoglobinopathy
(e.g. SS, SC.)
Hemoglobin H
Disease
Possible Diagnostic / confirmatory Tests
Presumptive diagnosis
Post-splenectomy
state
Liver disease
Hereditary - abeta –
lipoproteinemia
Lipoprotein
electrophoresis
Liver function tests
Abdominal
Ultrasound
DIC
TTP
HUS
Mechanical: eg,
Cardiac abnormality
Physical agents
Coagulation profile
PLT count
Renal function
Cardiac function
Schistocytes
Figure 2: Hemolysis: Morphological Changes on Blood Film
Yes
History / Physical
Blood Cultures
Family Evaluation:
- Osmotic Fragility
- EMA assessment
Immune hemolytic
anemia
Antibody ID
Medical History
Auto immune
disease?
HS
DAT-negative IHA
Clostridium sp.
Sepsis
Burn related
hemolysis
Hereditary
spherocytosis
Sepsis
Burns
Drug- induced
Auto-immune (1˚ or
2˚)
PCH
HDN
Hemolytic
Transfusion Reaction
Etiologies
© Copyright 2009 College of Physicians and Surgeons of Alberta
December 2009
Alberta Laboratory Quality Enhancement Program
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A LABORATORY APPROACH TO THE INVESTIGATION OF ANEMIA
Figure 3: Hypoproliferative Anemias
Specific Morphologic
Changes on Blood Film:
Microcytes
+/- hypochromia
Macrocytosis
+/- hypersegmentation
Thrombocytopenia,
Leukopenia or
Pancytopenia
Blast cells
Leukocytosis
+/- thrombocytopenia
+/- polycythemia
+/- basophilia
Iron deficiency anemia
Anemia of chronic
disease
Thalassemia trait
Liver disease
Vitamin B12 or
Folic acid deficiency
Medication effect
Alcohol effect
Aplastic anemia
Bone marrow
suppression due to drugs,
viral infection or
irradiation
MDS
Malignant infiltration
Granulomatous disease
Plasma cell neoplasm
Acute leukemia
Malignant lymphoma
Reactive leukocytosis
Myeloproliferative
disorder
CML
Serum Iron / TIBC
Serum Ferritin
Hgb Analysis
Bone marrow iron
assessment
Liver function tests
Vitamin B12 and
folic acid assays
Bone marrow studies
Bone marrow studies and
trephine biopsy
Serum/urine protein
analysis
Bone marrow with
cytogenetic analysis
Immunophenotyping (flow
cytometry or
immunohistochemistry)
Bone marrow and
trephine biopsy
Cytogenetic analysis
(JAK2, V627G mutation,
Philadelphia
chromosome, del (5q)
Presumptive diagnosis
Possible Diagnostic / confirmatory Tests
References:
1.
Glassy, Eric F., ed. - CAP Hematology and Clinical Microscopy Resource Committee. Color Atlas of
Hematology. 1998; 56-57, 68-69, 80-90, 94-99, 122, 126, 132, 165
2.
Bain, Barbara J. – Blood Cells – A Practical Guide. Fourth Edition. 2006; 70-71, 219, 230-231, 311-366.
3.
http://www.merck.com/mmpe/sec11/ch130/ch130b.html
4.
http://www.merck.com/mmpe/sec11/ch130/ch130e.html
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December 2009