Enzymes In Clinical Diagnosis Flashcards

1
Q

Where are most diagnostically important enzymes located?

A

Inside of cells w/in organelle or in cytosol

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2
Q

How do plasma enzymes happen most of the time?

A

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

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3
Q

How can plasma enzymes be measured?

A

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

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4
Q

Serum

A

Fluid obtained by centrifugation of coagulated whole blood

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5
Q

Benefit of using serum for tests

A

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

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6
Q

Disadvantage of using serum for tests

A

. 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

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7
Q

What are normal basal levels of enzymes in plasma from?

A

Normal cell turnover

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8
Q

What is inc. enzymes in blood plasma from?

A

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

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9
Q

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

A

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

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10
Q

Alkaline phosphatase abbrev. and tissue/organ source

A

. ALP/ALK

. Liver, bone osteoblasts

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11
Q

Gamma glutamyl transferase abbrev. and tissue/organ source

A

. GGT/GGTP

. Liver, pancreas

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12
Q

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

A

. ALT/SGPT

. Liver

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13
Q

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

A

. AST/SGOT

. Liver, muscle

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14
Q

Lactate dehydrogenase abbrev. and tissue/organ source

A

. LDH/LD

. Liver, muscle, erythrocytes

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15
Q

Creatine kinase abbrev. and tissue/organ source

A

. CK/CPK

. Muscle

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16
Q

basic metabolic panel tests what things?

A
. Glucose
. Ca
. Na
. K
. CO2
. Cl
. BUN
. Creatinine
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17
Q

Comprehensive metabolic panel tests what?

A

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

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18
Q

Where do amylase and lipase originate from?

A

Pancreas

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19
Q

What is used to assess prostate?

A

Acid phosphatase (prostate specific antigen, PSA)

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20
Q

What to use lab results for?

A

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

21
Q

Gaussian distribution

A

. 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

22
Q

How many STD are reference ranges established from?

A

+/- 2 STD

23
Q

Reference ranges for Skewed distributions

A

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

24
Q

How reference ranges for cholesterol are established

A

. Epidemiological data

. Values above 200 = high

25
Q

Factors affecting chemistry profile test results

A

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

26
Q

Interindividual variations

A

. BIological variations between individuals

. Age, sex, genetics

27
Q

Intraindividual variation

A

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

28
Q

T/F Intraindividual variation is less than interindividual variation

A

T

29
Q

Critical difference

A

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

30
Q

Isoenzymes

A

. 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

31
Q

Lactate dehydrogenase structure

A

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

32
Q

Isozymes and their components components of lactate dehydrogenase

A
. I1: HHHH
. I2: HHHM
. I3: HHMM
. I4: HMMM
. I5: MMMM
33
Q

Creatine kinase structure

A

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

34
Q

Creatine kinase isozyme components

A

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

35
Q

Enzymes in MI and when they peak

A

. CK-MB peaks in plasma 18 hrs after MI

. LD-1 peaks in plasma 36-40 hrs after MI

36
Q

Troponin complex structure

A

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

37
Q

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

A

. Max. Velocity

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

38
Q

Unwanted effects of enzyme activity

A

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

39
Q

Immunological activity assay

A

. 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

40
Q

Advantages of immunological assays

A

. 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)

41
Q

Electrophoretic separation

A

. 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)
.

42
Q

Renal Profile in metabolic panels

A

BUN, B/C, Uric acid, creatinine

43
Q

Liver profile in panels

A

ALP, GGT, ALT, AST, LDH, Bilirubin

44
Q

Muscle profile in panels

A

AST, LDH, CPK

45
Q

What does LDH catalyze

A

inter conversion of L-lactate and pyruvate

46
Q

Which isoenzyme form of LDH is specific for diagnosing MI?

A

LD1

47
Q

Which isoenzyme of LDH is most specific doe diagnosing liver dysfunction

A

LD5

48
Q

Which CPK isoenzyme is most specific in diagnosing MI?

A

CPK-MB (CPK2)