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HEMA LAB 2 > MODULE 4: PRE-ANALYTICAL VARIABLES AND COAGULOMETRY > Flashcards

MODULE 4: PRE-ANALYTICAL VARIABLES AND COAGULOMETRY Flashcards

1
Q

PRE-ANALYTICAL VARIABLES

A
  1. Patient management (part of the physician)
  2. Needle selection
  3. Collection tubes
  4. Venipuncture procedures
  5. Sample transport and storage
  6. Preparation of specimens based on tests to be performed
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2
Q

Needle bore should be sufficient to prevent hemolysis and to
prevent the activation of ____ and ____

A

platelets and procoagulants

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3
Q

Hemolysis, such as in traumatic venipuncture
■ There will be a _____platelets and coagulants

A

a premature activation

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4
Q

Hemolysis has

A

shortened
coagulation test

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5
Q

Adult with good veins :needle gauge and length

A

20 or 21 gauge, thin-walled, 1.0 or 1.25
inches long

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6
Q

Child or adult with small,
fragile, or hardened veins :needle gauge and length

A

23-gauge, winged-needle set (butterfly
set); collect with small evacuated tubes or
syringe

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7
Q

Transfer of blood from
syringe to tube

A

19-gauge safety transfer unit; slowly inject
through tube closure

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8
Q

Sodium citrate Concentration:

A

0.105 to 0.109 M

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9
Q

MW =

A

294.1 Daltons

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10
Q

9:1 ratio

A

9 parts whole blood to 1 part anticoagulant

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11
Q

○ Ratio of anticoagulant to whole blood: 1:9

A

■ 0.3 mL of anticoagulant + 2.7 mL of whole
blood

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12
Q

Calculation of anticoagulant (to adjust) if Hct is >55% or >0.55L/L:

A

C= (1.85 X 10-3) (100-H) V

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13
Q

What will happen if there will be increased volume of the RBCs
compared to the plasma or the anticoagulant?

A

the result of the coagulation test can be prolonged since
there will be less concentration of the plasma coagulation
factors because of the increase level of RBCs

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14
Q

What if the sample is already collected and the number of RBCs is
increased but noticed late? (Hct: 57%)
Remedy:

A

First, calculate the amount of sodium citrate needed
● Recollect specimen

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15
Q

x-axis

A

% Hematocrit

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16
Q

y-axis

A

mL of sodium citrate remaining in the tube
volume of the sodium citrate to be adjusted

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17
Q

preserves Factors V and VIll better

A

SODIUM CITRATE

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18
Q

If the Factors V and VIlI cannot be
preserved in the sample

A

Leads to prolonged
coagulation time

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19
Q

Why is EDTA not used?

A

● Only for hematological procedures
● inhibits fibrinogen-thrombin reaction

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20
Q

Factor____ is unstable in its presence

A

V

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21
Q

Frothing (or bubbles) of sample

A

Shortened coagulation time

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22
Q

Short draw

A

PT and PTT are falsely prolonged coagulation time

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23
Q

Specimen clot : Partially clotted

A

Shortened coagulation time

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24
Q

Fully clotted

A

Prolonged coagulation time

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25
Q

Visible hemolysis

A

Shortened coagulation time

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26
Q

premature release of thromboplastin-like substances from the hemolyzed cells

A

Visible hemolysis

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27
Q

Lipemia or icterus

A

Prolonged coagulation time

28
Q

Tourniquet
application >1
minute

A

Shortened coagulation time

29
Q

Specimen storage
at 1-6° C
Due to activation coagulation factor VIl and platelets

A

Shortened coagulation time

30
Q

precipitation of large von Willebrand factor multimers
● destruction of platelet integrity.

A

Prolonged coagulation time

31
Q

Specimen storage
at >25° C

A

Prolonged coagulation time/tests

32
Q

ambient temperature

A

15-25 c

33
Q

activates factor VIl, activates
platelets, and precipitates large WF
multimers

A

1-6 c

34
Q

heat deteriorates coagulation factors
V and VIll (labile factors)

A

> 25 C

35
Q

Storage in household freezer

A

-20c and 2 weeeks

36
Q

Storage for 6 months

A

-70c and 6 months or indefinite

37
Q

If any assay cannot be
performed immediately

A

Centrifuge within 1 hour of collection

38
Q

To use frozen specimens
after storage

A

Thawed rapidly at 37°C
● Running water or water bath
Tested within 1 hour of the time it is
removed from the freezer

39
Q

If thawed frozen
samples cannot be
tested immediately

A

Stored at 1°C to 6°C (refrigerated
temperature) for up to 2 hours after
thawing

40
Q

What if 2 specimens are requested for a patient who does not undergo
heparin therapy (PTT and PT)?
Analyze within:
●___ PTT, PT
● ___: PT only
● The sample is centrifuged but the red cell and plasma is not
separated

A

4 hrs and 24 hrs

41
Q

Platelet Rich Plasma

A

Light transmittance aggregometry

42
Q

Platelet Poor Plasma

A

Clot-based testing
(coagulation testing)

43
Q

200,000 to 300,000/uL

A

PRP

44
Q

PRP Centrifugation:

A

50 x g for 30 minutes
(less revolution/minute or
centrifugal force)

45
Q

PPP
Centrifugation:

A

1500 x g for 10-15 minutes or
4400 x g for 3 minutes

46
Q

Excessive/vigorous mixing of
blood
● O

A

Shortened coagulation time

47
Q

Incorrect dilution of reagents

A

shortened

48
Q

Use of dirty tubes

A

Shortened coagulation time

49
Q

Anemic patient

A

Shortened coagulation time

50
Q

Examples of manual

A

Tilt tube and wire lopp

51
Q

Timer is initiated and stopped by
the operator

A

Manual

52
Q

Instrument usually contains a
device for maintaining constant 37°
C temperature

A

Semiautomated

53
Q

Analyzer may internally monitor
temperature
Instrument has a mechanism to
initiate a timing device
automatically on addition of final
reagent and a mechanism for
detecting clot formation and
stopping the timer

A

Semiautomated

54
Q

● Measures a change in conductivity between two metal
electrodes immersed in plasma

A

MECHANICAL or ELECTROMECHANICAL

55
Q

When a clot forms, the ___ conducts current between
the two probes.

A

fibrin strand

56
Q

The ___ inside the cuvette will stop moving when the fibrin
clot is formed

A

steel ball

57
Q

Involves detection of a change in optical density (absorbance)
● Formation of fibrin threads causes light to scatter allowing less
light to fall on the detector

A

PHOTO-OPTICAL (TURBIDOMETRIC)

58
Q

PHOTO-OPTICAL (TURBIDOMETRIC) Mechanism:

A

Fibrin thread or clot formation → scatter → detection of light is
decreasing → timer stops

59
Q

Modification of photo-optical detection in which 90-degree or forward-angle light scatter, rather than OD, is measured

A

NEPHELOMETRIC

60
Q

Employs a colorless synthetic oligopeptide substrate conjugated
to a chromophore - para-nitroaniline (pNA) - 405 nm

A

CHROMOGENIC

61
Q

Principle
of chromogenic

A

Hemostatic factor cleaves the chromogenic substrate at the site
binding the oligopeptide to the pNA, freeing the pNA.

62
Q

OD is proportional to the activity
of the analyte being measured

A

Direct chromogenic assay

63
Q

Change in OD is thus inversely
proportional to the concentration
or activity of the substance being
measured

A

Indirect chromogenic assay

64
Q

We use latex agglutination
○ Uses latex particles coated with antibodies

A

immunologic

65
Q

Principle of immunologic

A

Latex microparticles are coated with antibodies directed against
the selected analyte (antigen).

66
Q

Two of the most used global coagulation assays especially
in the hospitals

A

THROMBOELASTOGRAPHY (TEG) and ROTATIONAL
THROMBOELASTOMETRY (ROTEM) and THROMBIN GENERATION ASSAYS (TGA)

67
Q

Differentiate TEG and ROTEM vs TGA

A

Used for patients undergoing
surgeries or in trauma cases for TEG and ROTEM while Measures general physiologic
mechanism for hemostasis for TGA

HEMA LAB 2 (1 decks)

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