Download CBC Basic Interpretation - Thalassemia Center

CBC
Basic Interpretation
Tanim I. Aziz, MBBS
CBC…
• is one of the most common laboratory tests in medicine.
Typically, it includes the following:
• White blood cell count (WBC or leukocyte count)
• WBC differential count
• Red blood cell count (RBC or erythrocyte count)
• Hematocrit (Hct)
• Hemoglobin (Hb)
• Mean corpuscular volume (MCV)
• Mean corpuscular hemoglobin (MCH)
• Mean corpuscular hemoglobin concentration (MCHC)
• Red cell distribution width (RDW)
• Platelet count
• Mean Platelet Volume (MPV)
How does CBC come ?
• Circulating blood cells, including red blood cells
(RBCs), white blood cells (WBCs), and platelets, are
counted and sized electronically by modern instruments.
• One such instrument, the Coulter counter, generates an
electrical pulse when a blood cell passes through a small
aperture surrounded by electrodes.
• Each electrical pulse represents an individual cell, and
the pulse height indicates the cell volume. Therefore, the
electronic counter not only registers the total cell count
but also estimates the average cell volume and the
variation in cell size.
• In the context of RBCs, these measurements are
referred to as the mean corpuscular volume (MCV) and
the RBC distribution width, respectively.
• Modern electronic counters are also capable of
multimodal assessment of cell size and content,
thus providing additional information about the
various categories of WBCs including neutrophils,
lymphocytes, monocytes, eosinophils, and basophils
(ie, 5-part differential).
• Two other “measured variables” of the complete
blood cell count (CBC) are hemoglobin (Hgb) and
hematocrit (Hct).
• The Hg is computed by a spectrophotometer after
RBCs are lysed in a given volume of blood and the
Hgb is chemically converted into a stable pigment.
• The Hct is determined by a microhematocrit
centrifuge and represents the percentage of a
given volume of whole blood that is occupied by
packed RBCs.
• However, Hct also can be calculated by
multiplying the RBC count and the MCV.
• Other “calculated” variables in the CBC include
the mean corpuscular Hg content (and mean
corpuscular Hg concentration; these 2 calculated
values are rarely used in routine clinical practice.
ANEMIA
Microcytic
(MCV <80 fL)
Normocytic
(MCV 80-100 fL)
Macrocytic
(MCV >100 fL)
MICROCYTIC ANEMIA
The 3 major diagnostic possibilities for
microcytic amaenia are :
• Iron deficiency anemia (IDA),
• Thalassemia,
• Anemia of chronic disease (ACD)
IDA
•
•
•
•
RBC: normal or low
Hb: low
MCV: low
RDW: high
Thalassemia
•
•
•
•
RBC: normal or high
Hb: low
MCV: low
RDW: normal
Disproportionate !!!
An extremely low MCV may
suggest Alpha – thalassemia !!!
• The CBC count and peripheral blood film
examination results are usually sufficient to suspect
the diagnosis.
• In the severe forms of thalassemia, the Hb level
ranges from 2-8 g/dL.
• MCV and MCH are significantly low, but, unlike
thalassemia trait, thalassemia major is associated
with a markedly elevated RDW, reflecting the
extreme anisocytosis.
• The WBC count is usually elevated in b thalassemia
major; this is due, in part, to miscounting the many
nucleated RBCs as leukocytes.
• Platelet count is usually normal, unless the spleen is
markedly enlarged.
Mentzer index
• Is used to differentiate IDA from Bthalassemia.
• MCV / RBC : is < 13, thalassemia is more
likely.
• If the result > 14, then iron-deficiency
anemia is more likely.
ACD
•
•
•
•
RBC: normal or low ?
Hb: low
MCV: normal
RDW: normal
Macrocytosis
Common causes:
• Drug-induced
• Nutritional
• Liver disease, alcohol use
• Hypothyroidism
Macrocytosis
•
•
•
•
RBC: normal
Hb: normal or low
MCV: high
RDW: normal or high
WBC
• Leukopenia….
• Leukocytosis….
Lots of differentials….do not forget to match
with the clinical features presented…
Leucopenia
Common causes:
• Chemotherapy
• Radiation therapy
• Leukemia (as malignant cells overwhelm the
bone marrow)
• Myelofibrosis
• Aplastic anema
• Medications
– Clozapine (anti-psychotic)
– Immunosuppressive drugs
– Interferons
Other causes :
• Influenza
• Systemic lupus erythematosus
• Typhus
• Malaria
• HIV
• Tuberculosis
• Dengue
• Rickettsial infections
• Enlargement of the spleen
• Folate deficiencies
• Psittacosis
• Sepsis
Pseudoleukopenia
• It can develop upon the onset of infection.
• The leukocytes are marginalized in the blood vessels so
that they can scan for the site of infection.
• This means that even though there is increased WBC
production, it will appear as though it is low from a blood
sample, since the blood sample is of core blood and does
not include the marginalized leukocytes.
• Valproic Acid…
Leukocytosis
Neutrophil leucocytosis (neutrophilia >7.5x109/l):
Infection:
acute bacterial infection
Inflammation /
necrosis:
myocardial infarction or ischaemia
trauma
vasculitis
Myeloproliferative
disorders:
polycythaemia rubra vera
myelofibrosis
chronic granulocytic (myelomonocytic)
leukaemia
Metabolic:
uraemia / acidosis
gout
eclampsia
Malignancy:
any other malignancy
Drugs:
steroids
Blood loss:
acute haemorrhage or haemolysis
Lymphocytosis:
Acute viral infection (usually associated with
rubella
pertussis
mumps
infectious mononucleosis
most other acute viral illnesses
Chronic viral infection:
hepatitis B and C
Bacterial infections:
tuberculosis
brucellosis
whooping cough
acute bacterial infections in infants
Other causes:
thyrotoxicosis
autoimmune disorders
lymphoma
lymphocytic leukaemias
neutropaenia):
Thrombocytopenia
Decreased production
– Vitamin B12 or folic acid deficiency
– Leukemia
– Decreased production of thrombopoietin
– Sepsis, systemic viral or bacterial infection
– Hereditary syndromes
• Congenital amegakyrotic thrombocytopenia
• Thrombocytopenia absent radius syndrome
• Fanconi anemia
• Bernard-Soulier syndrome associated with large platelets
• Meg-Hegglin anomaly
• Grey platelet syndrome
• Alport syndrome
Increased destruction
–
–
–
–
–
–
–
–
–
–
–
–
Idiopathic thrombocytopenic purpura (ITP)
Thrombotic thrombocytopenic purpura (TTP)
Hemolytic-uremic syndrome (HUS)
Disseminated intravascular coagulation (DIC)
Paroxysmal nocturnal hemoglobinuria (PNH)
Antiphospholipid syndrome
Systemic lupus erythematosus (SLE)
Post-transfusion purpura
Neonatal alloimmune thrombocytopenia (NAITP)
Hypersplenism
Dengue fever
HIV
Thrombocytosis
• Do not necessarily signal any clinical
problems, and are picked up on a routine
full blood count.
• A full medical history must be elicited to
ensure that the increased platelet count is
not due to a secondary process.
• Thrombopoetin…an acute phase
reactant…
Thrombocytosis
Essential (primary)
– Essential thrombocytosis (a form of myeloproliferative
disease)
– Other myeloproliferative disorders such as chronic
myelogenous leukemia, polycythemia vera,
myelofibrosis
Reactive (secondary)
– Inflammation
– Surgery (which leads to an inflammatory state)
– Hyposplenism / spleenectomy
2.9
9.8
27
60
16.5
3.2
17.3
350
Thank You !!!