Module 5

Question 1

What is the purpose of calibration curves/standard graphs?

Answer 1

To determine the concentration of unknowns.

Question 2

What info is required on a calibration curve?

Answer 2

Analyte name

Name of analysis method (reagent)

Instrument name/number

Date

Wavelength

Tech ID

Question 3

How are samples with readings above the linear range read?

Answer 3

They must be diluted, the absorption reread and calculated from the calibration curve and multiplied by the dilution factor.

Question 4

What else is the linear range known as?

Answer 4

Analytical or reportable range.

Question 5

When do instruments need to have new calibration curves made?

Answer 5

If a component is changed.

If new/different reagents are used.

Question 6

What are standards?

Answer 6

Pure solutions of analyze with known or predetermined concentrations.

AKA calibrators

Question 7

What is stock standard?

Answer 7

Concentrated standard used to make working standards.

Allows for longer storage.

Dilutions are easier to prepare.

Question 8

What are working standards?

Answer 8

Dilutions of the standard stock prepared in smaller volumes to create a calibration curve.

Question 9

Why is light transmitted less than incident light?

Answer 9

Loss of radiation due to:

Absorption of the substance to measured

Scattering of light

Reflection of the cuvette wall

Absorption by the solvent or reagent

Interfering substances

Question 10

What is a reagent blank?

Answer 10

Contains reagent and diluent instead of sample.

Question 11

What is the purpose of the reagent blank?

Answer 11

Accounts for the colour of the reagent.

Used as zero concentration standards.

Set as 0A

Question 12

What is a sample blank?

Answer 12

Contains the sample but diluent instead of reagent.

Question 13

What is the purpose of a sample blank?

Answer 13

Accounts for the colour of the sample.

Question 14

When are sample blanks required?

Answer 14

Coloured samples that contain interfering substances.

Question 15

What are controls?

Answer 15

Commercially prepared samples with known concentrations of various analytes.

Question 16

What is the purpose of controls?

Answer 16

Carried through procedure as a patient sample to detect procedural errors.

If a control result falls outside the control range it indicates a problem.

Question 17

When are controls used?

Answer 17

For every procedure performed.

Question 18

What is the matrix of the control?

Answer 18

The same as the patient samples.

Question 19

What is slope?

Answer 19

The direction and steepness of the curve.

Slope=rise/run or change in y/change in x

Question 20

What is the intercept?

Answer 20

Where the curve intercepts the x or y axis.

y = mx + b

Question 21

What is the intercept of the reagent blank?

Answer 21

The origin

Question 22

What is sensitivity?

Answer 22

The ability to detect or measure small changes in concentration.

Question 23

How does sensitivity affect the absorbance measured?

Answer 23

Small changes in concentration cause big changes in the signal measured (absorbance).

Steeper slopes- better sensitivity

Max A gives the max sensitivity

Question 24

What is a calibration curve?

Answer 24

Plot of the absorption of at least three standards against their known concentration.

X- axis- concentration

Y-axis- absorbance

Question 25

Why would a wavelength other than Max A be selected to determine absorption?

Answer 25

To extend the assay’s linear range (wider concentration range).

To reduce absorption by interfering substances.

Question 26

How can sensitivity be reduced?

Answer 26

Changing the wavelength from Max A.

Decreasing the amount of sample relative to reagent (less product).

Decreasing the light path.

Diluting the final reaction mixture.

Question 27

What is the minimum detection limit?

Answer 27

The smallest concentration of an analytes that can be distinguished from zero.

Influenced by sensitivity.

Question 28

How are results

Answer 28

As less than MDL (not 0).

Question 29

What is the procedure for measuring patient samples?

Answer 29

1. Prepare standards of known concentration.
2. Measure standards.
3. Plot standard readings.
4. Measure controls- determine procedure validity.
5. Measure patient samples- compare to reference range.