haematology and anaemia Flashcards
list 4 laboratory blood tests
- haemocytometer (RBC count)
- microhaematocrit (% RBCs by volume of total blood)
- microscopic examination of blood smears
- automated analysers
describe the microhaematocrit test
- measures the ratio of the volume occupied by packed red blood cells to the volume of the while blood = PCV
- rapid and cheap in house test that gives large amount of information
what are the measured values important in haematology testing
- RBC: absolute number per litre
- mean corpuscular volume (MCV): the average volume of the red cells
- platelets: absolute number per litre
- haemoglobin: the amount of haemoglobin in the blood (g/l)
what is PCV
packed cell volume = hematocrit. this is the fraction of whole blood volume that consists of red blood cells
PCV = MCV x RBD count / 100
what is mean corpuscular hemoglobin
the average amount of hemoglobin per red blood cell in picograms
MCH = Hb x 10/RBC count
what is mean corpuscular hemoglobin concentration
the average concentration of hemoglobin in the cells relative to size/volume of the cell
MCHC = Hb x 100/Hct
what are some limiations of automated haematology counters
- they will not give reliable differential white cell counts (especially if there are abnormalities). even laser based in-clinic analysers and even combined laser/impendance analysers are also not perfectly reliable
- occasionally small RBCs will be undercounted and counted as platelets
- large platelets may get counted as red cells (common in some breeds)
- cant ID RBC morphology, WBC morphology or blood parasites
list some common problems with blood samples
- incorrect tube selection (incorrect anti-coagulant for the test requested)
- clotting
- haemolysis
- inappropriate tube fill
- liaemia
- no labelling (species esp)
what can you discern from microscopic examination of blood smears
- differential leukocyte counts, diversity of leukocyte patterns in cats and dogs
- erythrocyte and leukocyte morphology
- presence of any abnormal cells and parasites
- platelet countes
- send with EDTA sample for blood analysis to distinguish the effect of sample aging during transport and genuine diagnostic findings
- quick and low cost diagnostic tool
what is anaemia and what are the variables that distinguish it
condition in which the capacity of the blood to transport oxygen is reduced
due to:
- reduced number of circulating erythrocytes
- reduced amount of hemoglobin per erythrocyte
- both
defined by 3 basic variables:
- total hemoglobin
- PCV or haematocrit
- RBC count
anaemia can be caused by
- loss of blood (trauma causing hemorrhage, parasite infestations, etc…)
- lysis of erythrocytes (transfusion reactions, bacterial infections, neonatal erythrolysis)
- reduced production of erythrocytes (lead poisioning, iron deficiency, renal disease, viral disease, lymphoma/leukaemia)
how is anaemia characterisec
RBC morphology
1. cell size (macrocytic, normocytic, microcytic) = MCV
2. haemoglobin content (hypochronmic, normochromic, herperchromic) =MCHC
bone marrow response
3. reticulocyte count (regenerative if reticulocytes are higher than normal range, non-regenerative if normal or low)
how does renal disease/failure affect erythropoiesis
kidneys cant produce EPO, bone marrow cant produce RBC
