Lab Exam 1 Flashcards
hemacytometer use
manual WBC, RBC, platelet counts and body fluid cell counts
depth and depth factor of hemocytometer
0.1 mm
10
area of each large square (9 total)
1 mm^2
area of each small square (25 in one large)
0.04 mm^2
counting area for WBCs
4 large corner squares
4 mm^2
counting area for RBCs
5 small squares in the center square
0.2 mm^2
counting area for PLTs
large center square (1 mm^2)
or 5 small squares if count in large square is >40
boundary line rules
- double line —count cells touching innermost top and innermost left side lines
- triple line—count cells touching innermost lines, and cells touching middle top and middle left side lines
WBC count dilution
1:20 with acetic acid
1.9 mL diluent. + 0.1 mL sample
RBC count dilution
1:200 with 0.9% saline
first, make 1:10 with 0.1 mL sample + 0.9 mL saline
then, make 1:20 dilution with 0.1 mL previous + 1.9 mL saline
PLT count dilution
1:100 with ammonium oxalate
the higher the dilution…
the more statistical error inherent in the procedure
formula for calculating cell counts
(# cells)(depth factor)(dilution factor)/counting area = cells/μ
when diluting for WBCs or PLTs, let sample sit for —- mins before charging hemocytometer to…
10 min
lyse RBCs
let cells sit in hemocytometer for —– min to…
10
let them settle into same plane
sources of error in manual count
- clumped/clotted/rouleaux
- chipped or scratched coverslip
- improper filling
- not mixing sample
- tech error when counting
normal RBC, WBC levels for an adult
RBC female: 3.8-5.2 x 10^6 cells/μL
RBC male: 4.5-5.9 x 10^6 cells/μL
WBC: 4.0-11.0 x 10^3 cells/μL
principle of manual hgb test
lysis of RBCs and conversion of hgb to methemoglobin, which is read on the spec
reagent, dilution, and wavelength of manual hemoglobin
SLS (sodium laurel sulfate)
1:250
540 nm
3 functions of Hgb reagent
- lysis RBCs
- dilutes blood
- converts hemoglobin to methemoglobin
Beer’s law equation for finding Hgb concentration
(ABS unk/ABS std)(std conc) = unk conc
Hgb sample dilution procedure
5 mL SLS
remove 20 μL
add 20 μL sample
manual Hgb interferences
icterus
lipemia
high WBC ct
high plasma proteins
failure to lyse cells
failure to detect abnormal Hgb
hematocrit
proportion of blood that is RBCs
spun crit centrifuge must be standardized every ——
6 months
degree to RBC packing during spun crit depends on…
- speed
- time
- radius of centrifuge
- fullness of tube (3/4)
- trapped plasma
advantages of spun crit
- uses small amt of blood
- only takes 3 mins
- allows us to look at supernatant
disadvantages of spun crit
- trapped plasma
- somewhat subjective
- incomplete separation of RBCs and buffy coat
causes of increased hematocrit
pregnancy
hemoconcentration
polycythemia/polycythemia vera
hypoxia → EPO → erythropoiesis
causes of decreased hematocrit
anemias
excessive fluids
many more
rule of 3s
Hct = 3(Hbg) ± 3
sources of error for spun crits
- hemolysis
- not sealed well
- IV contamination
- measuring buffy coat
optimum spin time
time at which maximum packing occurs
MCV
definition
RR
terminology
calculation
average size of RBCs
80-100 fL
normocytic, microcytic, macrocytic
MCV = 10(Hct/RBC)
MCH
definition
RR
calculation
average weight of Hgb in RBCs
28-34 pg
MCH = 10(Hgb/RBC)
baby MCV
up to 105
MCHC
definition
RR
terminology
calculation
hemoglobin concentration in average RBC
32-36 g/dL
normochromic, hypochromic, spherocyte
MCHC = 100(Hgb/Hct)
causes of falsely elevated MCHC
- lipemia
- icterus
- hemolysis
- high WBC
- high protein
- cold agglutinins
causes of falsely decreased MCHC
- hyperglycemic osmotic effect
- IV contamination
RDW
definition
obtained from…
RR
unable to report when…
RBC distribution width
obtained from RBC histogram
12-15 (CV)
unable to report with dimorphic RBC population
anisocytosis
associated with which index?
variation in cell size
RDW
should always be used to check the indices
appearance of cells on smear