Hematocrit and RBC indicies Flashcards
Hematocrit reference range (Adult Males)
40 to 54% (0.40 to 0.54 L/L)
Hematocrit reference range (Adult Females)
35 to 49% (0.35 to 0.49 L/L)
Hematocrit reference range (Newborn)
53 to 65% (0.53 to 0.65 L/L)
Pertain to the instrument used to determine packed cell volume (PCV)
Hematocrit
The volume of red blood cells that have settled is called packed cell volume
Hematocrit
Hematocrit topmost layer
Fatty layer
Hematocrit second layer
Plasma
Hematocrit third layer
Buffy coat
Hematocrit fourth layer
Packed RBC
Hematocrit bottom layer
Plug (4-6mm)
Length of Micro-Hematocrit Tube
Approx. 75 mm
Inner bore of Micro-Hematocrit Tube
1.2 mm
Volume of blood a Micro-Hematocrit Tube can hold
0.05 mL
Length of the plug in a Micro-Hematocrit Tube
4 to 6 mm
Capillary tubes (red banded)
Heparin anticoag; used for direct capillary puncture
Capillary tubes (blue band)
No anticoagulant/plain; used for collection with anticoagulant
Significance of air bubbles in capillary tubes
Air bubbles denote poor skills but do not affect the test results
How to fill capillary tubes with a colored ring
Fill from the opposite end without the colored band
Hematocrit centrifugation
Spin for 5 minutes at 10,000 RPM
RPM check for hematocrit centrifuge
RPM must be checked periodically with a tachometer
Rodak’s Hematology centrifuge recommendation
Centrifuge at 10,000 g to 15,000 g for maximum packing
Test result agreement for two patient samples
Results should agree within 1% [+0.01 L/L]
Effect of trapped plasma on microhematocrit results
Causes microhematocrit to be 1% to 3% (0.01 to 0.03 L/L) higher than automated instrument results
Automated hematocrit
Calculated value from RBC and MCV
Conditions with more trapped plasma
Sickle cell anemia, Hypochromic anemia, Spherocytosis, Macrocytosis, Thalassemia
Effect of abnormal RBC shapes (e.g., spherocytes, sickle cells) on packing
inhibit complete packing
Causes of falsely increased hematocrit
Dehydration, Hemoconcentration, Insufficient centrifugation, Buffy coat inclusion
Causes of falsely decreased hematocrit
Hemolysis, Improper sealing, Increased AC concentration, Introduction of excess interstitial fluid
Rule of Three
Used to check validity of test results for normocytic, normochromic specimens
Rule of Three formula for RBC count
RBC count x 3 = Hb +/- 3
Rule of Three formula for Hemoglobin
Hb x 3 = Hct +/- 3
Mean Cell Volume (MCV) measures
Average volume of an individual RBC.
MCV formula
(HCT/RBC CT) x 10.
MCV reference range
80 to 100 femtoliters.
MCV in microcytic anemia
less than 80fL.
MCV in macrocytic anemia
greater than 100 fL.
Mean Cell Hemoglobin (MCH) measures
Average weight of hemoglobin in an individual RBC.
MCH formula
(Hb/RBC count) x 10.
MCH reference range
26-32 pg.
Mean Cell Hemoglobin Concentration (MCHC) measures
Mean concentration of hemoglobin in the average RBC.
MCHC formula
Hb/Hct x 100.
MCHC in hypochromic anemia
less than 31g/dL.
MCHC in hyperchromic RBCs
greater than 37 (true increase in Hereditary spherocytosis).
MCHC reference range
31-37 g/dL or %.
RBCs cannot hold more hemoglobin than
37 g/dL.
Result >37 g/dL for MCHC
Should be recomputed due to possible interference or inaccurate measurement.
MCH and MCHC clinical value
Have diminished but are valuable quality control tools.
Polycysthemia definition
Increased hematocrit level above normal.
Polycysthemia in clinical setting
Elevated hemoglobin and RBC count, reflecting elevated total erythrocyte volume.
Two types of polycythemia
Absolute and Relative.
Absolute Polycythemia
Elevated total red cell mass.
Relative Polycythemia
Normal total red cell mass, increased hematocrit due to decreased plasma volume.
Secondary polycythemia with appropriately EPO production (Absolute)
Decreased oxygen loading (hypoxia, high altitude, pulmonary disease, cyanotic heart disease, carboxyhemoglobinemia, methemoglobinemia, Hb M); Decreased oxygen unloading (high oxygen affinity hemoglobinopathy, biphosphoglycerate deficiency).
Secondary polycythemia with inappropriately EPO production (Absolute)
Neoplasms (Wilms’ tumor, renal carcinoma, cerebellar hemangioma, hepatoma); Localized tissue hypoxia (polycystic kidney, renal artery stenosis); Post-renal transplant, acute hepatitis.
Relative polycythemia
Diminished plasma volume (Dehydration, shock; Spurious Polycythemia: Stress polycythemia, Gaisböck’s syndrome.
Secondary polycythemia with Genetic polycythemia (Absolute)
Primary familial congenital polycythemia (mutated Epo receptor); Chuvash polycythemia (mutated VHL gene).
Secondary polycythemia with Primary marrow disorders (Absolute)
Polycythemia vera (PV).
Polycythemia vera (PV) characteristic
Panmyelosis (excessive proliferation in RBCs, megakaryocytes, granulocytes).
Polycythemia vera (PV) hallmark
Plethora.
Polycythemia vera (PV) mutation
JAK2 V617 mutation (90%-97% of patients).
Polycythemia vera treatment
Therapeutic phlebotomy (aim to maintain hematocrit < 45%) - also used for hemochromatosis
