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Clinical Chemistry II - 4378 > LAB EXAM 2- Pointe Scientific manuals > Flashcards

LAB EXAM 2- Pointe Scientific manuals Flashcards

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1
Q

Expected values for cholesterol?

A

<200 mg/dl

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2
Q

Principle for total cholesterol testing?

A

enzymatic method using cholesterol esterase, cholesterol oxidase, and peroxidase to produce red colored product that is directly proportional to the total cholesterol at 500 nm.

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3
Q

Cholesterol specimen collection/storage?

A
  • Non hemolyzed blood
  • Stable for 7 days at 18-25 degrees Celsius
  • When frozen and protected against evaporation, stable for 6 months
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4
Q

Cholesterol interferences?

A

see list of drugs that affects cholesterol

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5
Q

Cholesterol clinical significance?

A

used to monitor heart disease risk. Total cholesterol is measured to determine LDL levels by taking the total cholesterol minus HDL cholesterol minus triglycerides divided by five.

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6
Q

Cholesterol calculation?

A

(abs. sample) / (abs. standard) x conc. std. (mg/dl)

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7
Q

Cholesterol linearity up to _______ mg/dL

A

700

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8
Q

What does GGT stand for?

A

gamma-glutamyl transferase

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9
Q

What are the expected GGT values for males?

A

8-37 U/L at 30 degrees Celsius,

9-55 U/L at 37 degrees Celsius

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10
Q

What are the expected GGT values for females?

A

6-24 U/L at 30 degrees Celsius,

8-37 U/L at 37 degrees Celsius

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11
Q

GGT principle?

A

-GGT catalyzes transfer of glutamyl group from GLUPA-C to glycylglycine
-The amount of 5-amino-2-nitobenoate is proportional to GGT activity measured kinetically at 405 nm.

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12
Q

GGT specimen collection/storage?

A
  • Serum only
  • GGT activity is inhibited by most anti-coagulants
  • Stable up to 7 days at 2-25 degrees Celsius
  • Stable up to a month when at 4 degrees Celsius
  • Stable up to a year at -20 degrees Celsius
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13
Q

GGT interferences?

A
  • most anticoagulants, antiepileptic drugs (phenytoin and barbiturates) may falsely elevated levels.
  • Bilirubin up to 20 mg/dl will have negligible interferences (<5%).
  • Some drugs
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14
Q

GGT clinical significance?

A

can be used to help diagnose and treat liver diseases like alcoholic cirrhosis and primary and secondary tumors. Elevated GGT appears earlier and more pronounced than other liver enzymes in the case of obstructive jaundice and metastatic neoplasms.

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15
Q

GGT calculation?

A

(Δ abs/min x TV x 1000) / (MMA x SV x LP) = U/L GGT in sample

TV- total assay volume (1.100ml)
1000- conversion of ml to L
MMA- millimolar absorptivity of 5-amino-2-nitrobenzoate (9.5)
SV- sample volume (0.100ml)
LP- light path (1cm)

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16
Q

Amylase normal range?

A

serum: 25-125 U/L

-labs with different populations and geography may have alternate ranges

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17
Q

Amylase principle?

A

10 CNPG3
—–alpha-amylase—->
9 CNP + CNPG2 + 9G3 + G

-alpha-Amylase hydrolyzes the 2-chloro-p-nitrophenyl-alpha-D-maltotrioside
(CNPG3) to release 2-chloro-nitrophenol and form 2-chloro-p-nitrophenyl-alpha-
D-maltoside (CNPG2), maltotriose (G3) and glucose (G).
-The rate of increase in absorbance is measured at 405 nm and is proportional to the alpha-amylase activity in the sample.

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18
Q

amylase specimen type?

A

unhemolyzed serum

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19
Q

What anticoagulants CANNOT be used for amylase collection?

A

Citrate and EDTA because it binds calcium that is needed for amylase activity.

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20
Q

Amylase storage?

A

-stable 1 week at RT
-2 months at 2-8 degrees Celsius

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21
Q

Amylase interferences?

A

-macroamylase can cause hyperamylasemia (can lead to false diagnosis of acute pancreatitis
-bilirubin ( less than or equal to 30 mg/dl) and Hgb (less than or equal to 500 mg/dL) have negligible effects
-lipemic samples (less than or equal to 1,000 mg/dL) have no effect, generally

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22
Q

Amylase clinical significance?

A

amylase activity used to diagnose and treat diseases of the pancreas.

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23
Q

Amylase calculation?

A

***Δ abs/min x 3178 = U/L alpha amylase (DO THIS CALCULATION INSTEAD OF THE ONE BELOW)

(Δ abs/min x TV x 1000) /
(MMA x SV x LP) = U/L alpha-amylase in sample

TV = Total assay volume (1.025 ml)
1000 = Conversion of U/ml to U/L
MMA = Millimolar absorptivity of 2-chloro-p-nitrophenol (12.9)
SV = Sample volume (0.025 ml)
LP = Light path (1 cm)

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24
Q

Amylase:

how do you convert to SI units?

A

SI units (nKat/L)

multiply the U/L value by 16.67

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25
Q

Triglycerides normal range?

A

44-148 mg/dL (0.50 - 1.67 mmol/L)

*samples that exceed 1,000 mg/dL should de diluted and reassessed.

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26
Q

Triglyceride principle?

A

*Triglycerides → Glycerol + Fatty Acid (Lipase)
*Glycerol + ATP → Glycerol-1-phosphate + ADP (GK)
*Glycerol-1-phosphate + O2 → DAP + H2O2 (GPO)
*H2O2 + 4-AA + 4-chlorophenol → Quinoneimine Dye + HCl + 2H2O

-Triglycerides are hydrolyzed to glycerol & free fatty acids by lipase
-In presence of ATP & glycerol kinase, glycerol gets converted to glycerol-1-phosphate
-Glycerol-1-phosphate is oxidized by glycerol phosphate oxidase to yield hydrogen peroxide
-Hydrogen peroxide condenses with 4-cholorphenol & 4-AA in presence of peroxidase to produce a red colored dye
-The dye is measured at 500nm

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27
Q

Triglyceride specimen?

A

-fresh, clear, unhemolysed serum
-collected following 12 hour fast

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28
Q

Triglyceride storage?

A

-1 week at 2-8 degrees C
-3 months at -20 degrees C

-Frozen is thawed at RT and well mixed, do not refreeze

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29
Q

Triglyceride interferences?

A

-Not influenced by hemoglobin (less than or equal to 100 mg/dL) or bilirubin (less than or equal to 12 mg/dL [<5%])
-detergents affect lipase activity

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30
Q

Triglyceride clinical significance?

A

valuable for diagnosis/treatment of atherosclerosis, poor diabetes mellitus control, nephrosis, liver disease, or disease of lipid metabolism.

31
Q

Triglyceride calculation?

A

(Abs Unk / Abs Std) x Conc. Std.

32
Q

Convert triglycerides to SI units?

A

To convert the results into SI units (mmol/L), multiply the result (mg/dl)
by 0.0113.

33
Q

Glucose normal range?

A

70-105 mg/dl

34
Q

Glucose principle?

A

*D-Glucose + H2O2 + O2 →H2O2 + D-Gluconate (glucose oxidase)
*H2O2 + 4-AAP + Phenol → Quinonimine dye + H2O (POD)
-Glucose oxidase oxidizes glucose to gluconate & hydrogen peroxide
-Hydrogen peroxide produces a dye in the presence of peroxidase that can be measured at 500nm

35
Q

Glucose specimen collection?

A

-Non-hemolyzed serum or heparinized plasma is recommended
-Serum must be separated from the clot promptly since the rate of glucose decrease is approximately 7% per hour in whole blood.

36
Q

Glucose specimen storage?

A

-stable for 24 hours when refrigerated (2-8 degrees C)

37
Q

Glucose interferences?

A

-Bilirubin to the level of 20 mg/dl and Hemoglobin to a level of 500 mg/dl have
both been found to exhibit negligible interference (<3%)

38
Q

Glucose clinical significance?

A

diagnosis and treatment of diabetes mellitus.

39
Q

Glucose SI units?

A

To obtain results in SI units (mmol/L)….

multiply results in mg/dl by 0.0556

40
Q

Glucose calculation?

A

(Abs sample / Abs. standard) x concentration of standard (mg/dl)

41
Q

Direct bilirubin normal range?

A

0.5 mg/dl for adults and infants over one month

42
Q

Direct bilirubin principle?

A

-Sulfanilic acid reacts with sodium nitrite to produce diazotized sulfanilic acid
(diazo).
-Direct bilirubin couples with diazo to produce azobilirubin.

43
Q

Direct bilirubin specimen collection?

A

-Fresh, unhemolyzed serum is recommended

44
Q

Direct bilirubin speicmen storage?

A

-Samples should be analyzed within two hours of collection if kept at room
temperature in the dark and within twelve hours if kept refrigerated (2-8°C)
and protected from light.
-stable for 3 months when frozen at -20 degrees C
-Direct sunlight may cause up to a 50% decrease in bilirubin within one hour.

45
Q

Direct bilirubin interferences?

A

A number of drugs and substances affect bilirubin results.

46
Q

Direct bilirubin clinical significance?

A

to accesses and diagnose liver disease

*this measures conjugated bilirubin

47
Q

Direct bilirubin calculation?

A

(Abs. of Unk – Abs. of Unk Blank) / (Abs. of Cal – Abs. of Cal blank ) x Conc. of Cal (mg/dl)

48
Q

What does LDH stand for?

A

Lactate Dehydrogenase

49
Q

LDH normal range for males?

A

-50-166 U/L (30°C)
-80-285 U/L (37°C)

50
Q

LDH normal range for females?

A
  • 60-132 U/L (30°C)
    -103-227 U/L (37°C)
51
Q

LDH principle?

A

-Lactate dehydrogenase catalyzes the oxidation of lactate to pyruvate with
simultaneous reduction of NAD to NADH (this is measured).
-rate of NAD reduction can be measured as an increase in absorbance at 340nm.

*L-Lactate + NAD+ —LD—> pyruvate + NADH + H+

52
Q

LDH specimen collection?

A

-Non-hemolyzed serum is recommended. Red cells contain large concentrations of LD.
-The serum should be removed from the clot promptly
-Samples should be assayed soon after collection

53
Q

LDH storage?

A

-stable for 2-3 days at RT
-do not freeze or expose to high temps (37 degrees C), it may inactivate thermolabile LD isoenzymes

54
Q

LDH interferences?

A
  • Certain drugs and substances affect LD activity.
  • Bilirubin to the level of 20 mg/dl has been found to exhibit negligible interference (≤ 5%) in this assay.
  • Hemolysis has been shown to significantly interfere with the assay at levels
    as low as 100 mg/dl.
55
Q

LDH clinical significance?

A

-Increased levels of LD are associated with myocardial infarction
-Levels reach a maximum approximately 48 hours after the onset of pain and persist about ten days.
- degree of elevation is of value in assessing the extent
of damage and in developing a prognosis
-LD elevations are also observed in liver disease, pernicious anemia, in some cases of renal disease, and in
some cases of skeletal muscle trauma

56
Q

LDH SI units?

A

SI units (nkat/L), multiply result by 16.76

57
Q

LDH calculation?

A

IU/L = Δ abs. x 3376

58
Q

ALT normal range?

A

4 to 24 IU/L (30°C)
4 to 36 IU/L (37°C)

-Since the expected values are affected by age, sex, diet, and geographical location, each laboratory is strongly urged to establish its own reference range for this procedure.

59
Q

ALT principle?

A

-ALT catalyzes the transfer of the amino group from L-alanine to αketoglutarate resulting in the formation of pyruvate and L-glutamate.
-Lactate dehydrogenase catalyzes the reduction of pyruvate and the simultaneous oxidation of NADH to NAD.
-The resulting rate of DECREASE in absorbance is directly proportional to ALT activity

*L-Alanine + α-Ketoglutarate ——–ALT——–> Pyruvate + L-Glutamate

*Pyruvate + NADH + H+ ——LDH—–> L-Lactate + NAD+ +H2O

60
Q

ALT specimen collection?

A

-Hemolyzed samples cannot be used as red cells contain ALT

61
Q

ALT specimen storage?

A

-stable for 3 days at room temperature (15-30°C)
-7 days refrigerated (2-8°C)
-30 days frozen (-20°C).

62
Q

ALT interferences?

A

-number of drugs and substances affect ALT activity.
-Bilirubin to at least 30 mg/dl, and hemoglobin to at least 400 mg/dl, have been found to have a negligible effect

63
Q

ALT clinical significance?

A

-ALT is widely distributed in tissues with the highest concentrations found in
the liver and kidneys Even so, ALT is considered more liver-specific than AST
-Elevated levels of ALT are often only observed in liver diseases such as cirrhosis, hepatitis, or metastatic carcinoma.
-can also be elevated with infectious mononucleosis, muscular dystrophy,
and dermatomyositis.

64
Q

ALT SI units?

A

SI Units (nkat/L), multiply IU/L by 16.67

65
Q

ALT calculation?

A

∆Abs./Min x 1768

66
Q

AST normal range?

A

8 to 22 IU/L (30°C)
5 to 34 IU/L (37°C)

67
Q

AST principle?

A

*L-Aspartate + alpha-Ketoglutarate —–AST—–> Oxalacetate + L-Glutamate
*Oxalacetate + NADH + H+——-MDH—–> L-Malate + NAD+ +H2O
-AST catalyzes transfer of amino group from L-aspartate to α-ketoglutarate and yields oxalacetate and L-glutamate
-Oxalacetate undergoes reduction while oxidation of NADH occurs in the presence of malate dehydrogenase
*The resulting rate of decrease in absorbance at 340nm (NADH) is directly
proportional to the AST activity
*(LDH) is added to prevent interference from endogenous pyruvate which is normally present in
serum.

68
Q

AST specimen collection?

A

Non-hemolyzed serum is recommended. Red cells contain AST which can
give falsely elevated results.

69
Q

AST specimen storage?

A

-stable for 10 days when refrigerated (2-8 degrees C)
-2 weeks when frozen (-20 degrees C)
-4 days at RT (15-30 degrees C)

70
Q

AST interferences?

A

-A number of drugs and substances affect AST activity
-Patients with severe vitamin B6 deficiency could have a decreased recovery of AST, presumably due to a lack of pyridoxal phosphate.
-Bilirubin to at least 18 mg/dl, and hemoglobin to at least 300 mg/dl, have been found to have a negligible effect on this procedure.

71
Q

AST clinical significance?

A

-AST is widely distributed in tissues with the highest concentrations found in
the liver, heart, skeletal muscle and kidneys. Diseases involving any of
these tissues can lead to elevated levels
-Following myocardial infarction, AST levels are elevated and reach a peak after 48 to 60 hours.
-could indicate Hepatobiliary diseases such as cirrhosis, metastatic carcinoma or viral hepatitis
-elevated levels with muscular dystrophy, dermatomyositis, acute
pancreatitis and infectious mononucleosis.

72
Q

AST SI units?

A

SI Units (nkat/L), multiply IU/L by 16.67.

73
Q

AST calculation?

A

∆ Abs./min. x 1768

74
Q

One international unit (IU/L) is defined as…

A

the amount of enzyme that
catalyzes the transformation of one micromole of substrate per minute under specified conditions.

Clinical Chemistry II - 4378 (28 decks)

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