blood cells 4: blood result interpretation

Question 1

what causes hypochromia?

Answer 1

lower haemoglobin content / concentration / flatter cell. (hypochromia & microcytosis often go together)

Question 2

what causes hyperchromia?

Answer 2

thicker cells / abnormal cell shape

Question 3

what are the important types of hyperchromatic red cells?

Answer 3

spherocytes (spherical) & irregularly contracted (small & dense). cells

Question 4

what causes spherocytosis?

Answer 4

membrane not tethered to cytoskeleton in normal way

Question 5

what causes red cells to become irregularly contracted?

Answer 5

oxidant damage to membrane & haemoglobin

Question 6

what shapes can poikilocytes be?

Answer 6

spherocytes, irregularly contracted cells, sickle cells, target cells, elliptocytes, fragments (schitzocytes)

Question 7

what are target cells?

Answer 7

cells with an accumulation of haemoglobin in the centre of the area of pallor - occur in obstructive jaundice, liver disease, haemoglobinopathies & hypospenism

Question 8

what are elliptocytes?

Answer 8

ellipitical in shape, occur in hereditary elliptocytosis & iron deficiency

Question 9

what are sickle cells?

Answer 9

crescent shaped as a result of polymerisation of haemoglobin S

Question 10

what are fragments?

Answer 10

small pieces of erythrocytes - indicate a red cell has fragmented

Question 11

what are rouleaux?

Answer 11

stacks of red cells (sing. rouleau) - result from alterations in plasma proteins, common finding when there is infection / inflammation, particularly with presence of heavy proteins eg IgM

Question 12

what are agglutinates?

Answer 12

irregular clumps resulting from antibodies on the surface of erythrocytes

Question 13

how do agglutinates and rouleaux differ visually?

Answer 13

rouleaux = neat stack of coins, agglutinates = irregular messy stack of coins

Question 14

what is a Howell-Jolly body?

Answer 14

remnant of a nucleus in an erythrocyte (stains same dark purple as nucleus) - commonest cause is splenic function (as spleen usuallly removes nucleus)

Question 15

what other abnormalities are often seen on a film with Howell-Jolly bodies?

Answer 15

target cells & fragments

Question 16

what disease causes atypical lymphocytes?

Answer 16

infectious mononucleosis (glandular fever)

Question 17

what is toxic granulation?

Answer 17

heavy granulation of neutrophils - results from infection, inflammation & tissue necrosis (but is normal in pregnancy)

Question 18

what are hypersegmentated neutrophils?

Answer 18

increase in average number of neutrophil lobes / segments - usually results from lack of vitamin B12 or folic acid

Question 19

how can you tell if a patient is anaemic from a blood film?

Answer 19

low iron content -> low vicsosity -> bigger gaps between cells

Question 20

what is the difference between a reference & normal range?

Answer 20

reference is derived from a carefully defined population (mean +- 2SD = 95% population) but normal is more arbitrary

Question 21

what are the different parameters measured and their units?

Answer 21

WBC (x10^9/l), RBS (x10^12/l), Hb (g/l), Hct / PCV (% / l/l), MCV (fl), MCH (pg), MCHC (g/l), platelet count (x10^9/l)

Question 22

how are cells counted?

Answer 22

by automated instruments - thin stream of blood flows and electrical / light changes detected