Concepts of Clinical Testing

Question 1

What is an example of pre-analytical investigation?

sample collection - (whole blood? plasma? urine? cerebrospinal fluid?)

patient prep - (age of patinet, inpatient/outpatient ect)

Sample prep- (labelling, centrifuging)

Question 2

What is an example of analytical clinical testing?

Answer 2

use of any machine on a sample or clinical diagnostics

ie) photometric assay, immunoligical assay, ELISA etc

Question 3

What is a spectrophotometric assay used for?

Answer 3

measurement of light absorption over different wavelengths - can identify the protein in fluid using the absorption fingerprint

Question 4

What is acid phosphatase a biomarker for?

Answer 4

tumor marker = prostate cancer

Question 5

What is serum glutamic pyruvate transaminase (SGPT) and ALAT a biomarker for?

Answer 5

Hepatocellular damage

Question 6

What is alkaline phosphatase a biomarker for?

Answer 6

increased cholestatic liver disease

and

marker for bone disease

Question 7

What is serum glutamic oxaloacetic transaminase a biomarker for? (SGOT)

Answer 7

hepatocellular damage or muscle damage

Question 8

What is creatine kinase a biomarker for?

Answer 8

muscle damage and acute MI

Question 9

What is lactate dehydrogenase a biomarker for?

Answer 9

muscle damage

Question 10

What is the epitope?

Answer 10

it is the specific site on an antigen that an antibody binds to

Question 11

What is the ELISA method and what is it used for?

Answer 11

can be direct (antigen-antibody - enzyme)

or indirect (antigen- antibody - secondary antibody- enzyme)

or sandwhich (antibody- antigen - antibody - antibody - enzyme)

basically you coat a petri dish with an antigen solution and you use a flourescent antibody - to detect how much antigen you have on the dish

Question 12

How do we measure catalyzing enzyme concentration?

Answer 12

if the enzyme is a catalyst we can use the production of product as a measurement of enzyme concentration

Question 13

What is an example of an isotopic immunoassay?

Answer 13

Scintillation

Question 14

What is an example of a non-isotopic immunoassay?

Answer 14

chemiluminescence,

fluorescence, or photometry

Question 15

What is an example of a labelled immunoassay?

Answer 15

ELISA (enzyme - linked immunoabsorbent assays)

Question 16

Describe the process of a radioimmunoassay

Answer 16

this test measures small amounts of substance

• radioactive form of substance mixed with antibody and added to patients blood
• same substance (antigen) in blood competes with isotope for antiobody, leaving some of the radioactive substance free
• antibody bound isotope and ‘substance’ removed by precipitated with second antibody
• amount of free isotope measured and is presumed to be proportional to amount of original substance in the blood

Question 17

What is an emzyme multiplied immunoassay technique (EMIT) ?

Answer 17

it is an assay to analyze drugs, hormones, and metabolites - where Ag is added to tube containing antibody and substrate and you can measure enzyme activity by calculating the concentration of Ag from calibration curve

Question 18

What is Mass spectrometry?

Answer 18

It produces spectra of masses from molecules in sample and fragments of the molecules - it is used to determine the identify of unknown compounds by determining the mass and the matching to known spectra

Question 19

Which Elisa is more sensitive… indirect ELISA or Sandwhiched ELISA?

Answer 19

Sandwich ELISA - it amplifies the signal when you use secondary antibodies and the sandwich ELISA uses more secondary antibodies than indirect ELISA

Question 20

What are the stages of Mass spectrometry?

Answer 20

1) ionizer converts some of sample into ions
2) mass analyzer separates ions according to their mass-to charge ratio
3) detector records either charge induced or current produced when ion passes by or hits the surface

Question 21

What is the difference between accuracy and precision?

Answer 21

precise= exact measurement taken to a very small degree of variance

accurate = accurate means correct or free from errors - so it is on the mark exactly, but doesn’t necessarily mean that it’s right all the time

Question 22

What is the molar mass of a substance?

Answer 22

= molecular weight

ie) the mass of one mole of the substance (6.022 x 10^23 molecules)

Question 23

What is molarity?

Answer 23

moles of a substance (mol) / volume (L)

Question 24

What factors affect uncertainty of a measurement?

Answer 24

sample collection and transport

calibration, precision, and bias of assay

Question 25

what determines the reference range of a concentration?

Answer 25

the reference range is within 90-95% of a reference population - which depends on the age, gender, and ethnicity