Enzymes In Clinical Diagnosis

Question 1

Where are most diagnostically important enzymes located?

Answer 1

Inside of cells w/in organelle or in cytosol

Question 2

How do plasma enzymes happen most of the time?

Answer 2

. When membranes are damaged and enzymes inside them are released into fluid that surround cell

Question 3

How can plasma enzymes be measured?

Answer 3

. Whole blood draw, use serum prepared from it for lab assays

Question 4

Serum

Answer 4

Fluid obtained by centrifugation of coagulated whole blood

Question 5

Benefit of using serum for tests

Answer 5

Blood already clotted and doesn’t have any additives to prevent clotting

Question 6

Disadvantage of using serum for tests

Answer 6

. Hemolysis may occur while waiting for blood to clot before cells are separated from serum
. Lysis of these may release enzymes and cause fake pos. Results

Question 7

What are normal basal levels of enzymes in plasma from?

Answer 7

Normal cell turnover

Question 8

What is inc. enzymes in blood plasma from?

Answer 8

. Cell membrane injury (hepatitis, MI)
. Enzyme induction (response to drug metabolism)
. Tumor
. Cell proliferation (bone healing)

Question 9

Enzymes from specific tissues in plasma vs. enzymes that are general?

Answer 9

. Specific enzymes show that specific tissue has damage, general enzymes provides less specific indication of site of injury

Question 10

Alkaline phosphatase abbrev. and tissue/organ source

Answer 10

. ALP/ALK

. Liver, bone osteoblasts

Question 11

Gamma glutamyl transferase abbrev. and tissue/organ source

Answer 11

. GGT/GGTP

. Liver, pancreas

Question 12

Transaminases: alanine aminotransferase (serum glutamate-pyruvate transaminase) abbrev. and tissue/organ source

Answer 12

. ALT/SGPT

. Liver

Question 13

Aspartate aminotransferase (serum glutamate-oxaloacetate transaminase) abbrev. and tissue/organ source

Answer 13

. AST/SGOT

. Liver, muscle

Question 14

Lactate dehydrogenase abbrev. and tissue/organ source

Answer 14

. LDH/LD

. Liver, muscle, erythrocytes

Question 15

Creatine kinase abbrev. and tissue/organ source

Answer 15

. CK/CPK

. Muscle

Question 16

basic metabolic panel tests what things?

Answer 16

. Glucose
. Ca
. Na
. K
. CO2
. Cl
. BUN
. Creatinine

Question 17

Comprehensive metabolic panel tests what?

Answer 17

. Glucose, Ca, Na, K, CO2, Cl, BUN, Creatinine (what’s in BMP)
. Additional: total protein, albumin, ALP, ALT, AST, bilirubin

Question 18

Where do amylase and lipase originate from?

Answer 18

Pancreas

Question 19

What is used to assess prostate?

Answer 19

Acid phosphatase (prostate specific antigen, PSA)

Question 20

What to use lab results for?

Answer 20

. Aid in diagnosis
. Follow patient’s response to treatment, see adverse effect to drug therapy
. Make prognosis

Question 21

Gaussian distribution

Answer 21

. Bell shaped curve for normal test result ranges
. 67% normal healthy people w/in 1 STD of mean
. 95% Normal people w/in 2 STD of mean
. 9.7 normal people w/in 3 STD of mean

Question 22

How many STD are reference ranges established from?

Answer 22

+/- 2 STD

Question 23

Reference ranges for Skewed distributions

Answer 23

. Values ordered numerically and top and bottom 2.5% of results dropped to establish reference limits for tests

Question 24

How reference ranges for cholesterol are established

Answer 24

. Epidemiological data

. Values above 200 = high

Question 25

Factors affecting chemistry profile test results

Answer 25

. Change in patient’s condition . Analytical variation . BIological variation

Question 26

Interindividual variations

Answer 26

. BIological variations between individuals | . Age, sex, genetics

Question 27

Intraindividual variation

Answer 27

. BIological variation in one patient from one sampling to the next . Pregnancy, drug therapy, loses/gains weight, begins/end exercise program

Question 28

T/F Intraindividual variation is less than interindividual variation

Answer 28

T

Question 29

Critical difference

Answer 29

. Difference btw serial test results that must occur before significance can be claimed

Question 30

Isoenzymes

Answer 30

. Distinct variant forms of given enzyme . Catalyze same rxn as original enzyme but differ in physical properties . Present in different organisms, diff. Tissues of same organism, or in diff. Cells in same tissue

Question 31

Lactate dehydrogenase structure

Answer 31

. 4 subunits of 2 different types (H for heart and M for skeletal muscle) . Only tetramers have activity

Question 32

Isozymes and their components components of lactate dehydrogenase

Answer 32

``` . I1: HHHH . I2: HHHM . I3: HHMM . I4: HMMM . I5: MMMM ```

Question 33

Creatine kinase structure

Answer 33

. Active as diet w/ 2 types of subunits (B for brain and M for muscle)

Question 34

Creatine kinase isozyme components

Answer 34

. CK1: BB . CK2: MB . CK3: MM

Question 35

Enzymes in MI and when they peak

Answer 35

. CK-MB peaks in plasma 18 hrs after MI | . LD-1 peaks in plasma 36-40 hrs after MI

Question 36

Troponin complex structure

Answer 36

. 3 subunits . Inhibitory subunit (Troponin 1) . Tropomyosin binding subunit (troponin T) . Ca binding unit (Troponin C)

Question 37

What is proportional to amount of enzyme present in enzyme activity assays and what does this implicate?

Answer 37

. Max. Velocity | . More enzyme present in patient sample, greater rate at which product is formed (greater rxn velocity)

Question 38

Unwanted effects of enzyme activity

Answer 38

. PH, temp., cofactors/coenzymes, activators and inhibitors

Question 39

Immunological activity assay

Answer 39

. Amt enzyme present measured using antibody that recognizes and binds to enzyme . Antibody labeled and measurement of amt of bound labeled antibody correlates to amt enzyme present

Question 40

Advantages of immunological assays

Answer 40

. Enzyme doesn’t have to be active to be detected so unwanted effects of activity are eliminated (higher diagnostic sensitivity) . Isoenzymes can be distinguished from each other (greater diagnostic specificity)

Question 41

Electrophoretic separation

Answer 41

. Charged particles separated from each other in electric field . Separates isozymes bc they have slightly diff. Charges . Enzyme sample placed on solid support (gel) saturated w/ buffer of specific pH (alkaline) . Proteins neg. charged at alkaline pH an move towards anode (pos. Pole) .

Question 42

Renal Profile in metabolic panels

Answer 42

BUN, B/C, Uric acid, creatinine

Question 43

Liver profile in panels

Answer 43

ALP, GGT, ALT, AST, LDH, Bilirubin

Question 44

Muscle profile in panels

Answer 44

AST, LDH, CPK

Question 45

What does LDH catalyze

Answer 45

inter conversion of L-lactate and pyruvate

Question 46

Which isoenzyme form of LDH is specific for diagnosing MI?

Answer 46

LD1

Question 47

Which isoenzyme of LDH is most specific doe diagnosing liver dysfunction

Answer 47

LD5

Question 48

Which CPK isoenzyme is most specific in diagnosing MI?

Answer 48

CPK-MB (CPK2)