Unit 3.4 HEMATOCRIT (HCT) MEASUREMENT; RBC INDICES Flashcards
refers to the proportion of whole blood that consists of red blood cells, expressed as a percentage of the total blood volume.
Hematocrit (packed cell volume/PCV)
provides the clinicians with an estimate of the bods red cell volume and thus, the bloods ogen-carrying capacity.
Hematocrit
is useful in screening for, diagnosing, or monitoring a number of conditions and diseases that affect the proportion of blood (e.g. anemias).
Hematocrit determination
Other uses of hematocrit:
Used in the calculation of (?)
In rough (?)
The buffy coat portion can be used in the preparation of (?)
Absolute indices/constants
Quality Control calculations
buffy coat smears
Hematocrit Reference ranges:
Male:
Female:
0.42 - 0 .50 / 41.5 - 50.4%
0.36 - 0.45 / 35.9 - 44.6%
Indirect Hct Calculated as:
Direct (Manual/Spun Hct) Computed as:
Microhematocrit tube
Length: _________
75 mm
Microhematocrit tube
Bore: _________
Microhematocrit tube
Blood column:
at least 5 cm
Microhematocrit tube
Plug/Seal: ________
Microhematocrit tube
Centrifugation (RCF): __________
10,000 -15,000 g for 5 mins
Wintrobe Tube
Length: ___________
115 mm
Wintrobe Tube
Graduations:
Left: __________________
Right: __________________
Wintrobe Tube
Diameter: _____________
3mm
Wintrobe Tube
Centrifugation (RCF): __________
3,000 rpm for 30 mins
Technical Errors
Excess anticoagulant - leads to RBC shrinkage
Prolonged-standing of blood sample prior to test
Insufficient mixing of blood
Improper sealing of tube leads to escape of red cells
Inadequate centrifugation/allowing the tubes to stand too long after centrifugation
Reading errors (e.g. parallax error)
Physiologic Errors
Trapped plasma increases the (?)
Values taken immediately after (?)
Dehydration leads to (?)
Stasis which leads to (?)
packed cell volume/height
acute blood loss
plasma loss
hemoconcentration
To check the accuracy of the RBC, Hb, and Hct values generated by an automated analyzers or by manual methods.
RULE OF THREE:
The rules of three applies only to RBCs that are normal in
size and hemoglobin content
RULE OF THREE: BASIC FORMULA
If values are WITHIN and the RBCs are normocytic, normochromic =
report results
If values are NOT within & the RBCs are abnormal in shape & hemoglobin content =
report results
If values are NOT within but the RBCs are normocytic, normochromic =
Do NOT report
Used to define the size and hemoglobin content of the red blood cell.
RBC INDICES
Used in classifying types of anemia
RBC INDICES
refers to the average volume of the individual red cells in a given blood sample
MCV (Mean Corpuscular/Cell Volume)
Used as an estimation of the average size of the RBC
MCV (Mean Corpuscular/Cell Volume)
Not dependable when RBCs vary markedly in size
MCV (Mean Corpuscular/Cell Volume)
MCV =
MCV = Reference Value:
= Cells are microcytic
= Cells are macrocytic
80 - 100 fL
< 80 fL
> 100 fL
MCHC =
MCHC = Reference Value:
= Cells are hypochromic
= Cells are spherocytic
320 - 360 g/L or 32 - 36 %
< 32%
36%
MCH =
MCH = Reference Value:
27 - 33 pg
refers to average Hb concentration of red cells in a given volume of blood
MCHC (Mean Cell Hemoglobin Concentration)
The average weight of Hb per RBC
MCH (Mean Cell Hemoglobin)
Always correlate with the MCV & MCHC
MCH (Mean Cell Hemoglobin)
Directly proportional to the size of the RBC & the concentration of Hgb. in the cell.
MCH (Mean Cell Hemoglobin)
represents the ratio of the standard deviation to the MCV (width of the histogram)
RDW (Red Cell Distribution Width)
Index of relative anisocytosis; May also indicate poikilocytosis
RDW (Red Cell Distribution Width)
RDW (Red Cell Distribution Width)
Reference Value:
indicates variation in sizes
11.6 - 14.6 %
> 14.6%
Average amount of Hb in each RBC compared w/ the average amount in a normal RBC.
Color Index (C.I.)
C.I. =
C.I. = Reference Value:
0.9 1.1
%Hb =
% RBC =
Average size of a red cell as compared with the average size of a normal red blood cell
Volume Index (V.I.)
V.I. =
V.I. = Reference value:
0.9 1.1
% Hct =
Denotes the average amount of Hb per unit volume of RBC in relation to normal.
Saturation Index (S.I.)
S.I. =
S.I. = Reference value:
0.80 - 1.20
The average diameter of red blood cell in microns.
Mean Corpuscular Diameter (MCD)
Price Jones Method (Direct micrometry)
Mean Corpuscular Diameter (MCD)
Mean Corpuscular Diameter (MCD)
Reference value =
6-9 microns
Average volume of the biconcave disk
Mean Corpuscular Average Thickness (MCAT)
MCAT =
MCAT = Reference value:
1.7-3.5 microns
• Micro Method
• Macro Method
Direct (Manual/Spun Hct)
Wintrobe method
Double oxalate
Haden’s method
1.1% Na Oxalate
Van Allen
1.6% Na Oxalate
Sanford Magath Method
1.3% Na Oxalate
Bray’s Method
Heparin
Adams Micromethod
Heparin
Wintrobe Tube Sample
Undiluted anticoagulated blood
Westergren Method Sample
Original –
Modified –
whole anticoagulated blood w/ 3.8% Na Citrate (4:1)
2.0 mL EDTA blood combined w/ either 0.5 mL NSS or 0.5 mL 3.8% Na Citrate
Microhematocrit tube Length
75 mm
Wintrobe Tube Length
115 mm
Westergren Tube Length
300 mm ± 0.5 mm
Wintrobe Tube Internal bore:
3 mm
Westergren Tube bore:
2.65 ± 0.15
Westergren Tube Length of blood column:
200 mm
Microhematocrit tube Diameter:
1mm/1.2mm
Wintrobe Tube Diameter:
3mm
Westergren External diameter:
5.5 mm ± 0.5 mm
Microhematocrit tube RCF:
10,000 - 15,000 g for 5 mins
Wintrobe Tube RCF:
3,000 rpm for 30 mins
CLSI Specification of westergren tube:
thick-walled glass or hard plastic
Disposable Westergren ESR System
– has a safety plug (non-absorbent material) that provides automatic zeroing
Dispette
Vol. of capillary tube:
0.05 mL (2/3 is filled w/ blood)
Wintrobe Tube
2 Graduations:
(right);
(left)
Hct
ESR/sedimentation rate scale
Distance of tip to band
4-6mm
Technical Errors
• Excess anticoagulant - leads to RBC shrinkage
• Prolonged-standing of blood sample prior to test
• Insufficient mixing of blood
• Improper sealing of tube leads to escape of red cells
• Inadequate centrifugation/allowing the tubes to stand too long after centrifugation (<5 mins = false inc)
• Reading errors (e.g. parallax error – human error)
- leads to RBC shrinkage
Excess anticoagulant
(EDTA: inv)
6-8
leads to escape of red cells
Improper sealing of tube
Physiologic/Physical Errors
• Trapped plasma increases the packed cell volume/height – poikilocytes & anisocytes
• Values taken immediately after acute blood loss
• Dehydration leads to plasma loss
• Stasis which leads to hemoconcentration
REFERENCE RANGE Hematocrit
Male
0.42 - 0 .50
Female
0.36 - 0.45
Children
0.45 – 0.60
REFERENCE RANGE Wintrobe
Male
0-9 mm/hr
Female
0-20 mm/hr
Children
0-13 mm/hr
REFERENCE RANGE Westergren
Male
<50 y/o 0 -15 mm/hr
>50 y/o 0 -20 mm/hr
Female
<50 y/o 0 -20 mm/hr
>50 y/o 0 -30 mm/hr
Children 0 - 10 mm/hr
↑Hematocrit
• Polycythemia vera
• Hemoconcentration
• Dehydration
↓ Hematocrit
• Anemia
• Hydremia of pregnancy
• Hydration
↑MCV
• megaloblastic anemia (immature blood cell)
• hemolytic anemia with reticulocytes
• liver disease
• normal in newborns
↓MCV
• iron deficiency anemia (Pb binds w/ carrier prot of iron)
• thalassemia
• sideroblastic anemia (inc red cell incl)
• lead poisoning
↑MCH
• macrocytic anemia
↓MCH
• microcytic anemia
