Coag lab exam Flashcards
1
Q
2 platelet count methods
A
- manual (phase)
- automated analyzer
2
Q
platelet count sample
A
EDTA WB
3
Q
platelets are manually counted with the scope in ——– and on —x
A
phase
40
4
Q
diluent for plt count and function
A
1% ammonium oxalate
- preserves plts, WBCs, nRBCs
- lyses RBCs
5
Q
plt count dilution
A
1:100
1.98 mL ammonium oxalate + 20 μl blood
6
Q
a plt count dilution is good for —– hours
A
3
7
Q
plt clumping or satellitism
cause
solution
A
EDTA sensitivity
recollect in Na citrate
8
Q
3 methods of automated plt ct
A
- impedance (PLT-I)
- optical (PLT-O)
- fluorescent (PLT-F)
9
Q
A
10
Q
electric current is blocked as plts pass through
based on size only
A
impedance method
11
Q
impedance method of plt count interferences
A
- giant plts
- schistocytes
- small microcytes
- plt clumps
12
Q
uses light scattering properties to distinguish plts based on internal complexity
A
optical method
13
Q
uses fluorescent dye to stain plt organelles
A
fluorescent method
14
Q
RR and critical range for plt count
A
150-400 x 10^3/μL
<20 x 10^3/μL
15
Q
performed when plts are “flagged” on analyzer to verify accuracy of instrument’s count
A
platelet estimate
16
Q
uses a 20 μL capillary tube for dilution
A
manual platelet count
17
Q
let plt dilution sit for —– mins to allow RBCs to lyse
A
5
18
Q
which squares are plts counted in?
A
5 smaller squares (area of 0.2 mm^2)
if plt count <40 in these squares, count entire large center square
19
Q
plt count calculation
A
plts/μL = (plts counted)(100)(10)/0.2
100 = DF
0.2 = area
20
Q
plt estimate procedure
A
- scan entire feathered edge on 10x for clumps/fibrin strands
- in monolayer, count platelets in 5 fields and find average
- multiply average by 15 and 20 to get a range
21
Q
tests associated with primary hemostasis
A
- plt count
- bleeding time
- plt function assay
- plt aggregation studies
- flow cytometry
22
Q
tests associated with secondary hemostasis
A
- PT
- PTT
- TT
- Fibrinogen
23
Q
tests associated with fibrinolytic system
A
- FDPs
- D-dimers
24
Q
things to avoid during venipuncture
A
- TF entering sample
- do not draw tube with anticoag or clot promoter before the Na citrate
- hemolysis
- heparin contamination
25
how to avoid heparin contamination
- flush line with saline
- discard 1st 5 mL blood
26
coag tubes are ----- Na citrate with ------ anticoagulant:blood ratio
3.2%
1:9
27
function of Na citrate
chelates Ca++ in blood
28
if there is a sample volume <85% with Na citrate...
test results must be prolonged because excess additive will chelate Ca++ in the reagents
29
Hct ------ may prolong test results because less plasma requires less Na citrate
>55
30
what makes Na citrate a good additive?
- good preservative for factor V
- sensitive to heparin, so pts can be monitored
- better for ABS reading instruments because it doesn't create precipitate
31
-------- plasma is used for most coag tests
procedure
platelet poor
spin to reach plt <10,000/μL
32
handling and longevity of plt poor plasma
- good 4 hours RT or refrigerated
- 2 hours if pt on heparin
- keep capped until analyzed
- no repeated freezing/thawing
33
--------- plasma is used for plt aggregation studies
procedure
platelet rich
spin at lower speed to obtain plt count of 200-300 x 10^3
34
handling and longevity of plt rich plasma
- good for 3 hours RT
- do not freeze
35
why can't glass be used for coag samples?
negative charge causes contact activation of intrinsic pathway
36
old screen for platelet function
measures primary plt plug
bleeding time
37
factors that affect bleeding time
- plt function
- plt count (<100 will prolong, do count first)
- vessel integrity
- aspirin, clopidogrel (avoid 7 days prior)
- technique
38
automated screening method for plt function, which replaced bleeding time
platelet function assay
39
PFA uses a cartridge containing...
a collagen membrane coated with platelet agonist, such as epinephrine or ADP
40
collagen/epinephrine membrane used in PFA for...
plt dysfunction due to plt defects or inhibitors
41
collagen/ADP membrane used in PFA to...
determine if abnormal epinephrine result is due to aspirin
42
aspirin effect on PFA
epinephrine abnormal, ADP normal
43
what affects bleeding time but not PFA?
vessel integrity
44
sample handling for PFA
- do not spin
- cannot go through pneumatic tubes
- must stay at RT
- run within 3 hours
45
aggregating agents added
light transmission increases
aggregation studies
46
used to measure light transmittance for plt aggregation
aggregometer
47
aggregating agents
- collagen
- ADP
- epinephrine
- ristocetin
- arachidonic acid
48
no -------- 7 days prior to plt aggregation study
aspirin
49
monophasic pattern of plt aggregation
collagen
ristocetin
arachidonic acid
50
biphasic pattern of plt aggregation
ADP
epinephrine
51
biphasic pattern of plt aggregation occurs when...
ADP released from dense bodies of plts
52
ristocetin represents ----------- of plts and depends on interaction of ---- and -----
agglutination
vWF and GPIb
53
how to tell difference between ristocetin aggregation from VWD and from Bernard-Soulier syndrome
**VWD**: corrects with normal plasma added
**BSS**: does not correct with normal plasma added
54
flow can be used to dx...
Bernard-Soulier syndrome
Glanzmann thrombasthenia
55
most reagents for 2°hemostasis tests are ----------- and must be reconstituted with ----------
lyophilized
purified water (NERL)
56
when does QC for the 2° hemostasis tests need to be done?
- every 8 hours
- new reagent bottle
- after maintenance
- after problem with instruments or reagnets
57
fibrin endpoint systems detect...
unstable fibrin clot, factor XIII not yet activated (so XIII problems not detected)
58
2 automated methods for 2° hemostasis tests
- optical (ABS reading)
- mechanical (use a magnetic bead)
59
STAGO
evolution and compact instruments
use magnetic bead for 2° hemostasis tests
60
mechanical 2° hemostasis methods are not sensitive to...
hemolysis, icerus, lipemia
61
POC test used to estimate effectiveness of protamine sulfate dose (used to absorb heparin after cardiac surgery)
whole blood clotting time
62
---- used to monitor coumadin tx
---- used to monitor heparin tx
PT
PTT
63
not sensitive to slightly ↓ fibrinogen (must be <100 mg/dL)
PT
64
uses TF preparation to activate cascade by forming TF/VII complex and detecting clot
PT
65
PT RR
12-15 sec
66
how does each lab establish its PT RR?
run at least 30 normal plasma samples, half male and half female
67
--------- will not interfere with PT unless ↑↑
heparin
absorbent in reagent
68
coumadin action
inhibit production of vitamin K dependent factors in liver
69
used to standardize PT results for coumadin monitoring
international normalized ratio
70
ISI
international sensitivity index
supplied by manufacturer of each lot of thromboplastin for PT
71
INR =
**INR = R^ISI**
R = PR ratio = pt PT/mean normal PT
ISI supplied with reagent
72
INR TR
2.0-3.0
73
factors that affect efficacy of oral anticoag
- dosage
- vitamin K in diet
- body mass
- drugs (antibiotics, aspirin)
- liver function
74
why do antibiotics affect coumadin dosing?
↓ normal flora
↓ vitamin K made by them
↓ dose
75
↑ INR at risk for...
bleeding
76
3 uses for PTT
- detect deficiencies in intrinsic/common pathway
- monitoring heparin therapy
- detecting inhibitors
77
activated partial thromboplastin provides PL surface and activator with negative surface
CaCl2 provides Ca++
PTT
78
activators present in PTT reagent
kaolin
silica
79
PTT RR
25-35 sec
80
coag factors must be ------% of normal or less to cause abnormal PTT
25-40
81
is sensitive to slightly ↓ fibrinogen
PTT
82
better than PTT for monitoring heparin therapy
anti-Xa test
83
function of heparin
enhances action of ATIII on thrombin and Xa
neutralizes IXa and XIa
84
run PTT ---- hours after changing heparin dose
6
85
there is no standard, such as INR, available for...
PTT monitoring of heparin
86
how is heparin therapeutic range determined?
correlating PTT results from patients on heparin with Xa inhibition results
87
neutralize heparin
- PF4 (trauma, cold storage)
- protamine sulfate
88
Xa inhibition assay should be used...
- acute phase reactants present (early in DVT, PE)
- LMW heparin used
89
action of acute phase reactants on heparin
compete with ATIII for heparin binding sites, making PTT unreliable
used anti-Xa assay
90
prophylactic heparin given IM
usually doesn't need monitoring
LMW heparin
91
advantage of LMW heparin over unfractionated heparin
unfractionated heparin patients tend to make platelet Ab
LMW heparin does not cause this
92
anti-Xa is a ----------- assay using a standard curve
chromogenic
93
factor Xa inhibition assay TR
0.3-0.7 U/mL
94
deheparinzed plasma reagent can absorb up to ------ heparin
10 mL
95
use of deheparinized plasma
- remove heparin contamination
- for coumadin effect when pt is being converted from heparin to coumadin (if PT reagent sensitive to heparin)
96
mesaures conversion of fibrinogen to fibrin
TT
97
function of TT
look for circulating thrombin inhibitors
98
rate limiting factor in TT is...
thrombin in pt plasma
99
TT RR
15-19 sec
100
5 causes of abnormal TT
- FDPs
- ↓ fibrinogen
- dysfibrinogenemia
- thrombin inhibitor
- heparin
101
major difference between TT and Fib
**TT**: low level thrombin + undilute plasma
**Fib**: excess thrombin + dilute plasma
102
used to quantitate fibrinogen
Fib
103
Clauss assay reference method
Fib
104
TT performed on 1:10 dilution of plasma and control
Clauss method of Fib
105
rate limiting factor in Fib is...
pt fibrinogen concentration
106
Fib is ----------- to TT
inversely proportional
107
Fib RR
150-350 md/dL
108
performed if PT and PTT are normal, but pt is bleeding or clotting
FDPs/D-Dimer
109
FDP in plasma indicates ----- fibrinolytic activity
↑
110
FDP method
serum latex agglutination
111
conditions that can cause ↑ FDPs
DIC
liver/kidney/heart disease
MI
carcinoma
PE
DVT
eclampsia
112
D-dimer has excellent ---------- predictive value for DVT
negative
113
4 parts of DIC panel
PT
PTT
fibrinogen
D-dimer
114
↑ FDPs
normal D-dimer
fibrinogenolysis
115
differentiates factor deficiencies from circulating inhibitors
mixing studies
116
mixing study corrected =
mixing study not corrected =
factor deficiency
inhibitor
117
2 rounds of mixing studies
immediately
after 2 hours 37° incubation
118
time/temp dependent inhibitor
VIII
119
abnormal mixing study is followed by...
factor or inhibitor assay
120
uses single factor deficient substrate to determine if dilutions of pt plasma correct it
factor assay
121
factor assay corrected =
patient is not deficient
122
used with TT to differentiate FDPs, dysfibrinogenemia, and heparin contamination
reptilase time
123
enzyme that cleaves fibrinopeptide A
reptilase
124
reptilase time RR
18-22 sec
125
---------- time not affected by heparin
reptilase
126
TT ↑↑
reptilase ↑
FDPs
127
TT ↑
reptilase ↑↑
dysfibrinogenemia
128
TT ↑↑
reptilase normal
heparin contamination
129
uses extended incubation with first reagent in PTT
prekallikrein screening test
130
PK screen corrects =
prekallikrein deficiency
131
used to detect XIII deficiency
urea solubility test
132
fibrin clot is insoluble in 5M urea if...
XIII is present
133
5M urea clot dissolves =
XIII deficiency
134
plasma clotted with CaCl2
5M urea added
24 hour RT incubation
XIII screening test
135
XIII must be ------% to be detected and to be clinically significant
<1-2%
136
2 general types of assays for factor deficiencies
- activity assays - determine function
- immunoassays - determine quantity
137
RCoF assay
vWF activity assay
138
measures ability of vWF to agglutinate standard suspension of platelets in presence of ristocetin
RCoF assay
139
microtiter -------- used for vWF:Ag immunoassay
ELISA
140
↓ vWF:Ag
type I and III VWD
141
normal vWF:Ag
type II VWD
142
used to confirm type of VWD
SDS PAGE multimer analysis
143
all multimers of vWF ↓
VWD I
144
only HMW multimers of vWF ↓
VWD II
145
all multimers of vWF absent
VWD III
146
2 most common factor inhibitors
- lupus-like anticoagulant
- VIII inhibitor
147
inhibitor causing clotting
lupus-like
148
anti-PL inhibitor
lupus-like
149
3 steps to ID lupus-like inhibitor
1. clotting assay (prolonged PTT)
2. mixing studies
3. reduce or add excess PL to see if it corrects
150
plt neutralization procedure for LLAC
- ruptured platelets neutralize anti-PL
- if PTT corrects, LLAC is present
| false pos with heparin; PF4 neutralizes it
151
LLAC methods that use ↑ PL and ↓ PL
↑ PL: platelet neutralization; STAclot LA
↓ PL: dRVVT
152
dRVVT
dilute russel viper venom test
LLAC activity ↑ as PL content ↓
153
dRVV activates ----- in plasma
X
154
abnormal dRVVT ratio =
LLAC present
155
uses PTT reagent with increased PL content
STAclot LA
156
EIA test to pick up configurations of anti-PL that other tests don't detect
anti-cardiolipin Ab test
157
LLAC can bind PL on --------, blocking --------
VECs
protein C
158
uses dilute pt plasma with normal pooled plasma that has a known VIII activity
factor VIII inhibitor assay
159
thrombophilia
hypercoagulable state
repeated thrombotic episodes
160
ATIII assays use ------- as a target
thrombin or Xa
161
during ATIII chromogenic assay, thrombin releases ------------- from substrate
p-nitroaniline
162
more ATII = ------ color
↓
163
inherited deficiencies of ATIII
- ↓ ATIII
- dysfunctional ATIII
164
acquired deficiencies of ATIII
- DIC
- liver disease
- nephrotic syndrome
- OC/estrogen
- malignancy
165
protein C is quantitated by ----- assay
EIA
166
protein C assay uses -------- to activate PC
thrombin or thrombomodulin complex
167
protein C assay is based on ability of PC to ------------ PTT by...
prolong
inactivating Va and VIIIa
168
acquired protein C deficiencies
- DIC
- vit K deficiency
- liver disease
- oral anticoag
- postsurgical
169
2 forms of protein S
- free (40%), serves as cofactor
- bound to C4b (60%)
170
acquired protein S deficiencies
- liver disease
- pregnancy
- OC
- DIC
- T1DM
- oral anticoag
171
deficiency of ------ or excess of ------- seen in in inflammatory states, associated with hypercoagulation
t-PA
PAI-1
172
useful in monitoring fibrinolytic tx (used to dissolve existing clots)
antiplasmin assay
173
used to detect factor V leiden mutation
activated protein C resistance test
174
factor V leiden mutation causes...
V to be resistant to degradation by protein C
175
---- should be initially normal or FVL mutation test is invalid
PTT
176
used to confirm FVL mutation dx
PCR
177
effect of prothrombin mutation
↑ prothrombin levels up to 30% higher than normal
risk for thrombosis
178
deficiency of enzyme needed to convert homocysteine to methionine
methylene tetrahydrofolate reductase mutation
179
useful for TTP dx
ADAMTS-13 mutation or auto-Ab
180
vWF-cleaving protease
ADAMTS-13
181
unusually large vWF multimers
TTP
182
associated with ADAMTS-13 mutation
associated with auto-Ab against enzyme
chronic relapsing TTP
acute TTP
183
------ assay used for ADAMTS-13 antigen or Ab
ELISA
