Manual Methods—Bench Questions Flashcards
WBC dilution
1:20
3% acetic acid
1.9 mL + 100 uL
procedure for WBC estimate
average WBCs in 1/4 field on 10x
manual count if >20% discrepancy from analyzer
WBC correction for NRBCs
wbc(100)/(nrbc + 100) = corrected wbc
how closely should sides on hemacytometer match?
<25 cells: ±5 cells
>25 cells: within 20%
normal wbc ranges for adult and newborn
- adult: 4.3-10.0
- newborn: 5.0-30.0
causes of increased wbc
- infection
- leukemia
- pregnancy
- exercise
causes of decreased wbc
chemo
viral infection
myelodysplastic syndrome
plt dilution
1:100
ammonium oxalate
lyses rbcs, but not retics
area to count for plts
<200: 1 large square
>200: 5 small squares
normal plt
critical plt
- normal: 140-400
- critical low: <30
- critical high: >800
plt estimate procedure
average plts on 100x * 15 and 20 to give range value should fall in
why isn’t MPV calculated from manual count?
no way to calculate; derived from plt histogram
increased MPV
younger plts being released; thrombocytopenia
causes of thrombocytopenia
ITP
HIT
DIC
TTP
ALL
aplasic anemia
causes of thrombocytosis
IDA
CML
essential thrombocytosis
normal retic adult and newborn
- adult: 0.5-2.0%
- newborn: 2.5-6.5%
main causes of elevated retic
- hemolytic anemia
- blood loss
- thalassemia
- response to therapy for anemia
Miller Ocular calculation
cells counted out of 112/10 = %
corrected retic takes into account…
calculation
smaller pool of rbcs in pts with low hct
corrected retic = retics(hct/45)
retic index takes into account…
calculation
premature release of retics during anemia
retic index = [retics(hct/45)]/maturation time
shift/stress retic
retics released early when H&H are low to compensate
principle of sickle solubility
- saponin lyses rbcs
- Na hydrosulfite reduces released Hgb
- reduced Hgb S is insoluble in phosphate buffer, so suspension is cloudy
—–% sickling Hgb must be present for positive sickledex
10
sickling hemoglobins other than Hgb S
- Bart
- C Harlem
- C Georgetown
Hgb S mutation
Chromosome 11
glutamic acid replaced by valine
Hgb S disease & trait on electrophoresis
- disease: mostly Hgb S, some F and A2
- trait: 60% Hgb A, 40% Hgb S, small amount of F and A2
possible causes for false negative sickledex (2)
- pt too young, <10% Hgb S
- total Hgb <8 g/dL
sickledex procedure if Hgb <8
add 40 uL, not 20