Interpreting blood counts Flashcards
why is normal hard to define?
dependent on age, gender, ethnicity, physiological status, altitude, alcohol etc
how is a reference range derived?
from a carefully defined reference population
collect samples from healthy volunteers with certain characteristics
same instruments and techniques used as that that would be used on patients
how are blood counts analysed statistically ?
find Gaussian distribution
use mean
2SD to determine 95% range
Hb shows Gaussian distribution
what are the stipulations of using a reference range?
not all results outside reference range are abnormal and not all results within the range are normal
e. g. man with GI bleed with normal Hb count is not normal for the situation
e. g. 95% of people being overweight is not considered normal
what is an ideal test for blood counts in the populations?
when there is a clear distinction between sick and well people
you don’t want too much overlap
what are the cell counts and their units?
WBC – White blood cell – x109/L.
RBC – Red blood cell – x1012/L.
Hb – Haemoglobin – g/L.
PCV and Hct – Packed cell volume and Haematocrit (ratio).
MCV (fl)
MCH (pg)
MCHC (g/L)
platelets (x109/L).
what is the difference between MCH and MCHC?
MCH is the absolute amount of Hb in an individual RBC
MCHC is the concentration of Hb in the RBC
MCH tends to parallel MCV in anaemias
MCHC will change with shrinkage or growth of the cell i.e. takes into account volume and shape of the cell
while MCH will not change, raw Hb
how are WBC, RBC, platelets counted?
- visually on slide
- machines with electronic impulses generated everything a cell flows between a light source and sensor or electrical beam
how is Hb measured?
in spectrometer
convert Hb to stable form and measuring light absorption
what method is used to measure Hct and PCV?
centrifugation
how is MCV determined?
light scattering
interruption of electrical field
PCV/RBC
MCH
Hb/RBC
MCHC
Hb/PCV or Hb/Hct
how is MCHC measured?
light scattering
what cells show lead to a high MCHC?
irregularly contracted cells or spheroidal cells
what is polycythaemia?
too many RBCs in circulation
what is increased in polycythaemia?
RBCs
Hb, RBC and Hct all increase compare to normal subjects
how would you evaluate someone for polycythaemia?
clinical history- splenomegaly , abdominal mass or cyanosis
compare to normal range
what is the relative Hb, RBC and Hct in neonates, children, males and females and adults?
neonates have higher
lower in children than adults
lower in women than men
how can polycythaemia also present itself?
as pseudopolycythaemia
where there is actually a decrease in plasma volume (increase in concentration)
can be caused by dehydration/poor water intake
e.g. burns draw plasma out to surface
what can cause polycythaemia?
- doping (adding blood to your own)
- medical negligence (in transfusion)
- erythropoietin (when its too high, illicit or from ectopic or renal tumour)
- abnormal function of bone marrow
how does abnormal function of the bone marrow cause polycythaemia?
what is this called?
there is an inappropriate increase erythropoiesis without erythropoietin
“polycythaemia vera”
classed as myeloproliferative neoplasm, where a mutation has occurred
what can polycythaemia vera lead to?
this is erythropoietin-ndependent polycythaemia:
- hyper viscous blood leading to vascular obstruction
how do you treat polycythaemia?
removal of blood (venesection)
drugs- for intrinsic bone disease, reduction of RBC production
what does finger clubbing and cyanosis indicate?
hypoxia
four presentations
in young athletes (suspicious)
In breathless, cyanosed patient (hypoxia)
abdominal mass
splenomegaly
what is anisocytosis?
variable sized cells
what is poikilocytosis?
variable shaped cells
what are spherocytes and name a cause?
cells with a loss of membrane with an unequal loss of cytoplasm
hereditary spherocytosis
what are irregularly contracted cells and name a cause?
reduced central pallor in RBC
oxidant damage
what are sickle cells?
sickle shaped cells caused by haemoglobin S polymerisation
what are target cells and name causes?
cells with Hb accumulation in the central area of pallor
LIVER DISEASE, hyposplenism, haemoglobinopathies, obstructive jaundice
what is elliptocytosis and name caused?
elliptic RBCs
hereditary elliptocytosis, iron deficiency (paler cells compared to hereditary)
what are fragments? where are they seen?
aka schistocytes
red cell fragmentation like seen in SLE
what is rouleaux? cause?
stack of red blood cells
changes in plasma protein
what are agglutinates? cause?
irregular clumps of cells
antibodies on the surfaces causing stickiness
what are Howell-Jolly Bodies? cause?
nuclear remnants seen in cells
INDICATIVE of hyposplenism
what are Heinz Bodies?
round inclusions found just outside the cell
damage to Haemoglobin e.g. in G6PD deficiency (causing oxidant formation), alpha thalassemia and chronic liver disease
what is polychromasia?
blue tinge seen in cell cytoplasm indicative of a young cell i.e. reticulocyte
bone marrow damage
what percentage of WBCs are neutrophils?
75-80%
what are “drumsticks” in neutrophils?
Barr body:
female specific elements contains the inactivated X chromosome
what percentage of WBCs are lymphocytes?
20-25%
describe lymphocytes
round and regular
large dense nucleus
less cytoplasm
smaller than neutrophils
how do monocytes compare to neutrophils in size?
what are some key differences?
the same size
but have kidney shaped nucleus, grey-blue cytoplasm with no granules
what percentage of WBCs are eosinophils?
~1%
describe eosinophils
bi-lobed nucleus
larger orange-red granules
describe basophil granules
large purple granules that overlay the nucleus
what are the anaemia features of iron-deficiency?
key:
- microcytosis
- hypochromia
- anisocytosis
- poikilocytosis
- Target cells
- elongate cells (pencil)
- normal WBCs and platelets
what are the anaemia features of megaloblastic anaemia due to b12 deficiency?
(delayed nucleus maturation)
key:
- hypersegmented neutrophils
- macrocytosis
- anisocytosis
- poikilocytosis
- normal WBC and platelets
what are the anaemia features of sickle cell anaemia?
key:
- moderate neutrophilia
- polychromasia
- nucleated RBCs
- anisocytosis
- poikilocytosis
- Target cells
- sickle cells
- normal platelets
NB sickle cell anaemia causes reticulocytosis
what are the 2 causes of spherocytosis?
Hereditary spherocytosis
Autoimmune Haemolytic Anaemia
both involved spleen for removal
what does polychromasia indicate about the cells?
they are immature