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hematology > lecture 3 > Flashcards

lecture 3 Flashcards

1
Q

electric counters are only capable of measuring cell counts (T/F)

A

false, they are capable of measuring hematologic variables other than the cell counts

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2
Q

what are the advantages of electronic counters in comparison to the manual procedures?

A
  • rapidly analyze large numbers of samples
  • minimize technical errors
  • count much larger number of cells
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3
Q

equipment has evolved from ____ to _____ capable of producing as many as ___ hematologic measurements at a rate of ____

A
  • semi-automated, single-channel analyzers
  • sophisticated, multi-channel analyzers
  • 20 hematologic measurements
  • 140 blood specimens per hour
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4
Q

what are the 2 major types of automated cell counters?

A
  • those that depend on changes of impedance in electrical flow
  • those that employ light- scattering optics for cell enumeration
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5
Q

what type of automated cell counter is the coulter counter?

A

coulter counter is the best known and most commonly used counter employing the impedance principle

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6
Q

what is cell counting based on?

A

cell counting is based on the detection and measurement of changes in electrical impedance (resistance) produced by a particle as it passes through a small aperture

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7
Q

how is the flow of electrical current established in an electrical impedance principle?

A
  • the flow of electrical current is established between 2 electrodes immersed in an electrically conducted diluent
  • an insulated bridge with an aperture is placed between the electrodes
  • cells to be counted are suspended evenly into the diluent
  • the suspension is drawn through the aperture at a constant rate
  • the cells are poor conductors of electricity
  • the higher the cell volume (bigger) the higher the resistance
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8
Q

what does the number of pulses indicate?
what does the amplitude of the electrical pulse produced indicate?

A
  • nb of pulses indicate the nb of cells
  • the amplitude indicates the size/ volume of the cell
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9
Q

the impedance type of electrical counter is adaptable for accurate enumeration of which types of cells

A

RBCs, WBCs, platelets

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10
Q

For red cell measurement, the initial blood sample is diluted in an isotonic medium, in which both RBC(s) + WBC(s) are enumerated and counted in duplicate and each group is averaged. (T/F)

A

false, in triplicate

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11
Q

WBC and platelet counts are performed by counting platelets & WBC in whole blood (in the same chamber as RBC), but with a different threshold (T/F)

A

false, Platelet counts are performed by counting platelets in whole blood (in the same chamber as RBC), but with a different threshold. however, for WBC counting, the blood is diluted in a medium capable of lysing RBC(s).

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12
Q

when should we correct the WBC count?

A

when we have >5 NRBCs/100 WBCs

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13
Q

what is the formula used to correct WBC count?

A

Corrected WBC count= WBC count X 100
/ nRBCs + 100

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13
Q

what is the formula used to correct WBC count?

A

Corrected WBC count= WBC count X 100
/ nRBCs + 100

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14
Q

what does lyse S contain?

A

Lyse S contains potassium ferricyanide and potassium cyanide to change hemoglobin to cyanmethemoglobin (for Hb determination).

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15
Q

how does the optical cell counter works?

A
  • based on a light-scattering principle
  • diluted blood passes through a flow-cell detector placed in the path of a narrowly focused beam of light
  • when a blood cell passes through the flow cell, it causes measurable change in the light beam
  • in turn generates an electrical impulse
  • each impulse is counted
16
Q

what is the name of the special chamber used in manual cell counting?

A

hemocytometer

17
Q

what is ESR? what are some key points?

A
  • ESR (erythrocyte sedimentation rate) is the rate or speed of sedimentation of RBCs suspended in plasma
  • RBCs have a higher specific gravity than plasma, that’s why RBCs tend to fall to the bottom of the tube at a certain speed
  • screen for the presence or absence of active diseases
  • non-specific since it increases in a wide variety of diseases
18
Q

RBC(s) are suspended in the plasma for two reasons:

A
  1. The circulation of the blood keeps suspending the RBC(s) because they are in motion all the time.
  2. RBC surface carries a –ve charge which is caused by sialic acid.
19
Q

what are the factors that govern the speed of falling RBCs?

A
  1. number of RBCs in blood (the less the nb of RBCs, the higher the ESR)
  2. plasma viscosity (if plasma proteins increase, viscosity of plasma increases and ESR decreases)
  3. RBC mass (greater the mass, higher the ESR)
20
Q

what is the name of the condition where we have low nb of RBCs? how is the ESR affected?

A
  • anemia
  • ESR is high
21
Q

what is the name of the condition where we have high nb of RBCs? how is the ESR affected?

A
  • polycythemia
  • ESR is low
22
Q

how can we increase plasma viscosity?

A

add plasma proteins such as albumins, globulins, fibrinogen

23
Q

how can we increase the RBC mass?

A

by rouleaux formation (surface of one RBC is over the surface of another RBc => stacking)

24
Q

how are rouleaux formed?

A

fibrinogen and globulins remove the negative charge of the RBCs and allow them to stick together

25
Q

what causes rouleaux formation?

A
  1. fibrinogen
  2. globulins (gamma)

NOTE: albumins do not cause rouleaux formation

26
Q

albumins do not cause rouleaux formation (T/F)

A

true

27
Q

why albumins do not cause rouleaux formation?

A

for some reason they do not remove the negative charge of the RBCs => they don’t stick together

28
Q

what are some conditions that increase fibrinogen or gamma globulin?

A
  1. acute and chronic infections –> mostly increase gamma globulin
  2. any tissue damage (rheumatic fever, heart attack) –> mostly increases fibrinogen
29
Q

what plasma protein is an APR?

A

fibrinogen is an APR (acute phase reactant) that increases in response to stressful or inflammatory states

30
Q

what cells secrete gamma globulins?

A

plasma cells

31
Q

what is the name of the procedure that measures the ESR?

A

westergren’s method

31
Q

what is the name of the procedure that measures the ESR?

A

westergren’s method

32
Q

what is the procedure of the westergren’s method?

A
  1. we use a special Westergren pipette
  2. pipette is calibrated in mm starting from 0 at the top to 200mm at the bottom
  3. we fill the pipette with anticoagulated blood and leave it perpendicular in a rack unshaken for 1 hour
  4. we read the meniscus that separates the RBC layer/plasma
  5. record the distance the RBCs have fallen after 1 hr in mm/hr
33
Q

men and the elderly tend to have higher ESR levels (T/F)

A

false, women and the elderly

34
Q

what are the reference ranges for the ESR in healthy adults?

A

age <50 years:
- men 0-15
- women 0-20
age >50 years
- men 0-20
- women 0-30

35
Q

what is the difference between the automated ESR method and westergren’s method?

A
  • based on the same principle but accelerates the rate of sedimentation
  • takes 20 mins
  • recorded directly in mm/hr

hematology (10 decks)

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