classification and features of anaemia Flashcards
When is a person said to have anaemia
when the total hb count is less than what is expected for a person of a certain age,gender,and geographical location.
How does geographical location affect hb?
higher altitudes present with less oxygen.
people who reside in such areas will develop increased rbc ‘s in order to carry more oxygen.
Is anaemia a disease?
Anaemia is not a disease in itself, it is usually secondary to a disease.
General pathophysiology of anaemia
decreased hb/rbc–>decreased O2 carrying capacity–>hypoxia or hypoxia induced effect on organ –>signs of anaemia
classification of anaemia
Aetiologic
based on morphology
aetiologic causes of anaemia include
blood loss
low production of rbc
excessive destruction of rbc
Morphologic classification of of anaemia
Macrocytic anaemia
Microcytic hypochromic
Normocytic normochromic
what causes impaired RBC production
- lack of nutrients required for erythropoiesis ie folic acid, iron,vit B12
- Bone marrow failure causing decreased erythropoietin activity
- Anaemia cause by chronic conditions, i.e infections, kidney dx ,inflammatory disorders, connective tissue disorders
- Aplastic anaemia
- Anaemia from replacement of bone marrow. i.e in leukemia or lymphoma
Types of defects in RBC that cause anemia
- intrinsic defect in RBC ie membrane/Hb
Congenital ; hereditary spherocytosis, elliptocytosis ;sickle cell, thalassemia, unstable hb dx; pyruvate kinase deficiency, g6pd deficiency
Acquired ; paroxysmal nocturnal hemoglobinuria - Extrinsic defects
immune mechanisms; autoimmune acquired hemolytic anaemia;hemolytic dx of the newborn; March hemolytic anaemia
Acquired intrinsic defect that destroys RBC
Paraxosymal nocturnal haemoglobinuria
All extrinsic defects are
acquired
Paraxosymal nocturnal haemoglobinuria is
loss of protein on RBC that prevents it from being attacked by complement
Morphologic classification is based on
size
Hb content of RBC
Size of rbc
8 microns in diameter
Diameter comparable to the nucleus of a mature lymphocyte
What is it called when the size of RBC is normal
Normocytic
When the size of RBC is smaller than normal
microcytic
Diameter of RBC is bigger than normal
Macrocytic
when Hb content of RBC is normal
Normochromic
Normochromic RBCs have an area of central parlor 1/3 its size
Hb content lower than normal
Hypochromic
What is mean cell volume
Average volume of RBC in blood
Formula to calculate mean cell volume
Hematocrit %
………………………….. *10
RBC *10 raised to the power 12 /L
Unit for mean cell volume
femtolitre
Normal range of mean cell volume
81-100fL
What is mean cell haemoglobin
Average weight of hb in RBC
Formula for mean cell haemoglobin
Hbg/dl
———— * 100
Hematocrit %
Unit of mean cell haemoglobin
Picograms
Normal range of mean cell haemoglobin
26-34pg
what is mean cell hb concentration
Average concentration of hb in RBC volume
Formula for mean cell hb concentration
hb g/dl
——————- *100
hematocrit %
Formula for mean cell hb concentration
hb g/dl
——————- *100
hematocrit %
unit for mchc
grams per deciliter
Range for mchc
31-36 g/dl
What does hematocrit mean
fraction of volume of blood that red blood cells occupy
hematocrit in males
46%
Hematocrit in females
42%
Red cell distribution width
Checks range in volume and size of RBC.
Low value means cells are uniform
high value shows cells vary in size, usually due to presence of young RBC which are usually large. occurs in i.e pernicious anaemia; iron deficiency anaemia
Range for red cell distribution width
11.5%-14.5%
poikilocytosis
A condition where a number of RBCs are abnormally shaped
Formula for red cell distribution width
standard deviation of MCV
………………………………………….. *100
MCV
Normocytic Normochromic anaemia
Characterized by normal MCV,MCH,MCHC
Normocytic Normochromic anaemia
Characterized by normal MCV,MCH,MCHC
Normocytic Normochromic anaemia
Characterized by normal MCV,MCH,MCHC
Conditions where you’ll find normocytic normochromic anemia
Aplastic anemia increased plasma volume i.e in pregnancy,overhydration Blood loss kidney dx Anemia due to chronic disease
Microcytic hypochromic anemia
Characterized by low MCV,MHC,MCHC
Conditions associated with microcytic hypochromic anemia
thallasemia
lead poisoning
Macrocytic anemia
Characterized by raised MCV
Conditions where Macrocytic anemia occurs
Megaloblastic anemia; where bone marrow forms abnormally huge rbcs due to deficiency of folic acid or vitamin b12
Approach to anemic patient
take good history color of urine history in family examination of patient request appropriate investigations
History includes
diet number of pregnancies menorrhagia dark urine unusual bleeding family history of anemia
Physical examination includes
koilonychia of nails pallor of mucus membrane Examine mouth for glossitis or any lesions pedal edema jaundice check abdomen for masses/organs
Investigations include
- Reticulocyte count -high amounts mean RBCs are being depleted whiles low amounts mean theres a problem with bone marrow
- sickling test and Hb electrophoresis
- Blood film - RBCs stained for spherocytes etc
- coombs test for antibodies
- Thick and thin blood film for malaria and other infections
- G6PD test
- ESR and CRP test ; elevated in inflammatory conditions and plasma cell myeloma
