CC LAB LDH

Question 1

What method is used in Lactate dehydrogenase (LDH) Determination?

Answer 1

Kinetic Method by Buhl and Jackson, Modified by Wacker

Question 2

The enzyme lactate dehydrogenase is distributed in _____, ____, ____, and _______

Answer 2

Heart, liver,muscle and kidney

Question 3

Elevated serum levels are observed in?

Answer 3

Myocardial infarction, liver disease, certain forms of anemia, malignant diseases, and progressive muscle dystrophy

Question 4

Lactate to pyruvate method offers a number of advantages such as____?

Answer 4

Better reagent stability, elimination of pre incubation in the procedure, rate of reaction being linear over a wide range , and less contamination of NAD with inhibiting products

Question 5

LDH catalyzes the ___ of lactate to ____ in the presence of NAD, which is subsequently reduced to _____

Answer 5

Oxidation, pyruvate, NADH

Question 6

The rate of NADH formation measured at ______ is ___ to the activity of serum LDH

Answer 6

340 nm; directly proportional

Question 7

L-lactate + NAD <————> pyruvate + NADH + H+

Answer 7

LDH (ph 8.3 - 9.8)

Question 8

True or False: Lactate dehydrogenase does not act on D- lactate

Answer 8

True

Question 9

The pyruvate formed will proceed to the ______ for generation of energy

Answer 9

Embden-Meherhoff Pathway

Question 10

Colorimetric Method based on Wacker

A mixture of ____ and _____ reacts with NADH to produce a ______ compound.

Answer 10

Phenazine methosulfate and Nitroblue tetrazolium; blue colored compound

Question 11

The absorbance of this product is directly proportional to the amount of NADH present which in turn is proportional to the activity of LD in the sample.

Answer 11

Colorimetric method based on Wacker

Question 12

This method involves the conversion of pyruvate to lactate by LDH (pH 7.4-7.8) in the presence of NADH

Answer 12

Wroblewski and La Due

Question 13

True of False: The decrease in the concentration of NADH is measured and is directly proportional to the activity of LD in the sample. (Wroblewski and La due)

Answer 13

True

Question 14

True or False: In Wroblewski and La Due Method, the rate of forward reaction is 3x faster than the reverse reaction, allowing smaller sample volumes and shorter reaction time.

Answer 14

False: the rate of reverse reaction is 3 x faster than the forward reaction

Question 15

What are the methods for separation and quantitation of LDH isoenzymes?

Answer 15

Electrophoresis
Column chromatography
Immuno-inhibition
Babson’s Method
Kaplan and Berger
Using alpha-hydrobutyrate as a substrate

Question 16

True of False: LDH1 migrates the fastest and LDH6 being the lowest

Answer 16

True

Question 17

An LDH bound to immunoglobulin such as _____ and ____ migrate between LDH3 and LDH 4

Answer 17

IgA and IgG

Question 18

This method is employed for isolation of LDH1 and LDH2 for screening of acute myocardial infarction

Answer 18

Column Chromatography

Question 19

This method is used for the isolation of LDH1.

Answer 19

Immuno-inhibition

Question 20

(Immuno inhibition) : An antibody to the _____ of lactate dehydrogenase is assed to a serum sample

Answer 20

M sub-unit

Question 21

True or false: any isoenzyme containing an M-subunit binds to it, rendering the protein actively

Answer 21

False: inactive

Question 22

Which LDH does not contain the M subunit?

Answer 22

LDH1

Question 23

This measures the ratio of LDH1 to LDH5 by using solution of M-lactate to inhibit LDH1 and M-lactate- 1M urea to inhibit LDH5

Answer 23

Babson’s method

Question 24

This method involves determination f LDH1 using the rate of heart production in a batch type of colorimeter

Answer 24

Kaplan and Berger

Question 25

True or False: Using alpha-hydrobutyrate as a substrate; The M subunit has a greater affinity than that of the H subunit

Answer 25

False the H subunit has a greater affinity than that of the M subunit

Question 26

What enzyme is used in the utility for the measurement of LD1 activity

Answer 26

Alpha-hydroxybutyrate dehydrogenase

Question 27

True of false: It is not only specific to LD1 because LD2,3, and 4 also contains varying amount of H subunit

Answer 27

True

Question 28

True or False: hemolyzed specimen should not be used as red blood cells contain LDH activity 100-150 times that found in serum

Answer 28

True

Question 29

Sample and Assay considerations in LDH: For accuracy of results, It is advisable to analyze the sample immediately or within ____ hours of collection. In case of delayed processing, LDH is reported to be stable for _____ at room temperature

Answer 29

2 hours; 2 to 3 days

Question 30

True or False: The loss of activity occurs more quickly at 25 degrees Celsius than at 4 degrees Celsius

Answer 30

False: the lost of activity occurs more quickly at 4 degrees Celsius than at 25 degrees Celsius

Question 31

What isoenzyme is labile at cold temperature and is destroyed if frozen and thawned

Answer 31

Liver LDH

Question 32

____ and ____ compete with lactate for its binding site on the enzyme

Answer 32

Borate and Oxalate

Question 33

True or False; Heparin inhibit LDH activity by chelating zinc (role as an activator is not fully established )

Answer 33

EDTA

Question 34

True or False: pyruvate and lactate in excess cause inhibition of activity

Answer 34

True

Question 35

_____ is not recommended to use since a possible contamination with platelets exists

Answer 35

Plasma

Question 36

This method is linear up to an LDH activity of _____ IU/L. Samples exceeding this value should be diluted ____ (1:1) with ____, rerun and multiply results by two

Answer 36

800 IU/L; two-fold; deionized water

Question 37

What isoenzyme of LDH is measured in this assay?

Answer 37

Total lactate dehydrogenase

Question 38

What is the temperature limitation of the assay (LDH)

Answer 38

Temperature must be maintained within +/- 0.1 degrees Celsius

Question 39

____ specifically catalyzes the oxydation of lactate to pyruvate with the subsequent reduction of NAD to NADH

Answer 39

LD

Question 40

True or False; the rate which NADH forms is proportional to LD activity

Answer 40

True

Question 41

The method determines NADH absorbance increase per minute at ______

Answer 41

340 nm

Question 42

What are the reagent composition of LDH determination

Answer 42

L-lithium lactate NAD non-reactive stabilizers and fillers Buffer

Question 43

L- lithium lactate (____)

Answer 43

75.0 mM

Question 44

NAD (____)

Answer 44

5.5 mM

Question 45

Non-reactive stabilizers and fillers (____)

Answer 45

80mM

Question 46

Buffer (_____)

Answer 46

ph: 9

Question 47

What is the choice of specimen in LDH determination

Answer 47

Clear, non-hemolyzed serum

Question 48

Serum LDH is reportedly stable at ____

Answer 48

RT

Question 49

These isoenzymes are decreased in frozen samples

Answer 49

LD4 and LD5

Question 50

What inhibits the assay for LDH determination

Answer 50

Heparin, Oxalate,and Citrate

Question 51

What requires a serum blank in LDH determination

Answer 51

Icteric and Lipemic samples

Question 52

Multiplying factor of LDH determination

Answer 52

6592

Question 53

Total Assay Volume (____)

Answer 53

1.025 mL

Question 54

Millimolar Absorptivity for NADH (____)

Answer 54

6.22

Question 55

Sample volume (____)

Answer 55

0.025 mL

Question 56

Light path (_____)

Answer 56

1cm

Question 57

37-> 30C is multiplied by

Answer 57

0.6

Question 58

30C -> 37 C is multiplies by:

Answer 58

1.7

Question 59

Conversion factor

Answer 59

x16.67

Question 60

Reference value for men at 30 C

Answer 60

50-166 U/L

Question 61

Reference value for men at 37 C

Answer 61

80-285 U/L

Question 62

Reference value for females at 30 C

Answer 62

60-132 U/L

Question 63

Reference value for females at 37 C

Answer 63

103-227 U/L

Question 64

Linearity of LDH determination

Answer 64

800 IU/L

Question 65

Dry reagent should have a uniform __ or ____ appearance, and is stable at ____ until expiration date. Reconstituted reagent is stable for ___ at 2-8C.

Answer 65

White or Off-white appearance; 2-8C; 14 days

Question 66

Reagent absorbance greater than _____ (at 340 nm and 1cm light path) indicates deterioration

Answer 66

0.450