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HEMA > Week 3 Lab: Cyanmethemoglobin > Flashcards

Week 3 Lab: Cyanmethemoglobin Flashcards

1
Q

The cyanmethemoglobin is said to be the method of choice for hemoglobin determination because?

A
  1. Cyanmethemoglobin is stable in dilutions.
  2. Cyanmethemoglobin standard are readily available.
  3. All hemoglobin derivatives except sulfhemoglobin are measured with their conversion to cyanmethemoglobin.
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2
Q

Principle of cyanmethemoglobin method?

A
  • Hemoglobin iron is converted from ferrous to ferric state to form methemoglobin by the action of ferricyanide.
  • Methemoglobin then combines with potassium cyanide to produce the stable cyanmethemoglobin which is measured spectrophotometrically.
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3
Q

Patient preparation for cyanmethemoglobin method?

A
  1. Explain the test purpose.
  2. If your blood sample is being tested only for hemoglobin, you can eat and drink normally before the test.
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4
Q

Reagent used for cyanmethemoglobin method?

A

Drabkin’s Reagent

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5
Q

Drabkin’s Solution reacts with all forms of hemoglobin except __________, a pigment that normally occurs in only minute concentrations in blood.

A

sulfhemoglobin

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6
Q

Instrument used to measure the sample for cyanmethemoglobin method?

A

Spectrophotometer

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7
Q

A piece of laboratory equipment that is intended to hold samples for spectroscopic analysis.

A

Cuvette

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8
Q

What is the drawing located on the cuvette?

A

arrow

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9
Q

The arrow is located on which side of the cuvette?

A

clear side

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10
Q

Why do plastic cuvettes have two frosted sides?

A

The purpose of the frosted faces is to prevent light scattering out of the cuvette at the sides for certain types of samples.

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11
Q

Why is there an arrow on the cuvette?

A

This is to show which side of the cuvette to orient towards the spectrophotometer beam.

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12
Q

Procedure for cyanmethemoglobin method?

A
  1. Place 5 ml of Drabkin’s reagent into a test tube.
  2. Using Sahli pipette, draw blood to 0.02 cc mark. Make sure to wipe the outer wall of the pipette, and then dispense the blood to the test tube.
  3. Gently draw up and down to rinse the pipette and also to mix the resulting colloidal suspension.
  4. Cover and mix well by inversion. Let it stand for 5 minutes.
  5. Transfer the mixture to a cuvette.
  6. Set the spectro to 100% transmittance at the wavelength of 540 nm using a cyanmethemoglobin reagent blank.
  7. Continue reading the patient’s sample and record the percentage transmittance.
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13
Q

Place ___ of Drabkin’s reagent into a test tube.

A

5 ml

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14
Q

Using Sahli pipette, draw blood to ___ mark.

A

0.02 cc

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15
Q

Used to cover and seal cuvettes and test tubes.

A

parafilm

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16
Q

In cyanmethemoglobin method, we let the mixture stand for _____ before transferring it into the cuvette.

A

5 minutes

17
Q

In cyanmethemoglobin method, why do we let the mixture stand?

A

To allow the reaction between Drabkin’s reagent and blood to happen. (Sagot ko lang ‘to kasi wala akong mahanap sa google :-<)

18
Q

Set the spectro to ___ transmittance at the wavelength of ___ using a cyanmethemoglobin reagent blank.

A

100%, 540 nm

19
Q

Formula for converting percent transmittance (%T) to absorbance?

A

Abs = 2-log (%T)

20
Q

Formula for concentration of unknown in cyanmethemoglobin method?

A

Conc of unknown = (abs of unknown/abs of std) x value of std

21
Q

Reference value for males in cyanmethemoglobin method?

A

13.5-18.0 g/l

22
Q

Reference value for females in cyanmethemoglobin method?

A

12-15 g/l

23
Q

Clinical implications of cyanmethemoglobin method: decreased hemoglobin levels are found in?

A

anemia

24
Q

Clinical implications of cyanmethemoglobin method: increased hemoglobin levels are found in?

A

A. PV/Polycythemia vera
B. CHF/Congestive Heart Failure
C. COPD/Chronic obstructive pulmonary disease

25
Q

Sources of errors in cyanmethemoglobin method?

A
  1. Errors inherent in the sample
    - a. Blood sample collected through improper venipuncture
    - b. Blood sample collected through improper skin or capillary puncture technique
  2. Errors inherent in the method
  3. Errors inherent in the equipment
    - a. The accuracy of the equipment is not uniform
    - b. Unmatched cuvettes
    - c. Improper standardization of the photometer or colorimeter
  4. Operator’s error – human errors
26
Q

Human errors can be reduced by?

A
  • good training
  • understanding the clinical significance of the test and the necessity for a dependable method
  • adherence to oral and written instructions
  • familiarity with the equipment and with the sources of error

HEMA (13 decks)

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