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AUBF LAB > M3U3: BLOOD, PORPHOBILINOGEN, BILIRUBIN, AND UROBILINOGEN > Flashcards

M3U3: BLOOD, PORPHOBILINOGEN, BILIRUBIN, AND UROBILINOGEN Flashcards

1
Q

What is the usual urine colour for specimens of hematuria and hemoglobinuria ?

A

range from normal, pink, red and brown

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2
Q

How does hematuria and hemoglobinuria differentiate in clarity ?

A 
hematuria = cloudy/smoky appearance
hemoglobinuria = clear
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3
Q

what would alkaline pH urine promote in specimens showing hematuria and hemoglobinuria ?

A 
hematuria = lysis of intact cells
hemoglobinuria = hemoglobin oxidation
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4
Q

for specimens of hematuria and hemoglobinuria, what is shown after centrifugation ?

A 
hematuria = cell button
hemoglobinuria = uniform clear red urine
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5
Q

what is detected in the chemical methods used in the detection of blood and hemoglobin ?

A

heme, and other compounds containing it such as myoglobin and cytochrome

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6
Q

what is the colour range observed in the reagent strip method for blood ?

A

yellow (negative) to green (positive)

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7
Q

What is impregnated in the reagent pad for blood ?

A

tetramethylbenzidine (chromogen) and peroxide

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8
Q

The ___ causes the reduction of peroxide and oxidation of the chromogen, producing a colour change on the reaction pad.

A

pseudoperoxidase activity of the heme moiety

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9
Q

What is the chemical equation for the chemical reaction taking place in the reagent strip method for blood ?

A

H2O2 + Chromogen -> Oxidized chromogen + H2O

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10
Q

In the reagent strip method for blood ___ is observed when intact red cells are present and lysed on the reaction pad

A

mottled/speckled pattern

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11
Q

which brand of reagent strip in the method for blood uses dimethyldihydroperoxyhexane ?

A

chemstrip

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12
Q

Which brand of reagent strip detects 6-20 RBC/uL and 0.02-0.06 mg/dL ?

A

multistix

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13
Q

Which brand of reagent strip detects 5-10 RBC/uL and 0.02-0.03 mg/dL ?

A

chemstrip

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14
Q

What may be the cause for a false-positive result in the reagent strip method for blood ?

A

strong oxidizing agents (sodium hypochlorite) - oxidizes the chromogen instead of the heme moiety

bacterial peroxidases (from E. coli) - catalyzes the reaction of the reagent and chromogen despite the absence of the pseudoperoxidase activity of heme

blood contamination

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15
Q

What may be the cause for false-negative result in the reagent strip method for blood ?

A

ascorbic acid, reducing substances - tend to react directly with peroxide impregnated on blood reagent pad and removes it from the intended reaction, thereby preventing oxidation of the chromogen

procedural errors (e.g. failing to mix the sample prior to dipping the reagent strip)

high urine specific gravity - causes intact red cells in urine to become crenated and resist lysis which is necessary to detect heme

increased urine nitrite (>10 mg/dL)

presence of formalin

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16
Q

Originally, at what concentration is multistix and vchem brand of reagent strips affected by ascorbic acid on the blood test ? and after the modification ?

A 
multistix = ≥9 mg/dL
vchem = ≥5 mg/dL

25 mg/dL

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17
Q

What modifications where done on the multistix and chemstrip reagent strip to reduce interference with ascorbic acid ?

A

multistix = uses a peroxide that is less subject to reduction by ascorbic acid

chemstrip = overlays the reagent pad with an iodate-impregnated mesh that oxidizes ascorbic acid prior to reaching the reaction pad

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18
Q

what is the principle of the salt precipitation method (blondheim test) qualitative test for blood ?

A

larger hemoglobin molecules are precipitated by ammonium sulfate and myoglobin remains in the supernatant

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19
Q

what is the possible results for the blondheim test ?

A

myoglobin present = supernatant (red), blood reagent strip (positive)

hemoglobin present = red precipitate, blood reagent strip of supernatant (negative)

20
Q

what is the principle of the benzidine test in other qualitative tests for blood ?

A

In the presence of the pseudoperoxidase activity of hemoglobin or myoglobin, hydrogen peroxide is decomposed to water and oxygen.

The liberated oxygen oxidizes benzidine to a green or blue colour

21
Q

what is the principle of the occult tablet test in other qualitative tests for blood ?

A

sodium carbonate + tartaric acid = CO2
- effervescence to facilitate the reaction

Tartaric acid and calcium acetate + strontium peroxide = hydrogen peroxide
- in the presence of pseudoperoxidase activity of hemoglobin or myoglobin, hydrogen peroxide is decompose to water and oxygen

Liberated oxygen oxidizes o-toluidine to a blue colour

red dye is added to mask discolouration of the tablet by blood

22
Q

What is the result for Guaiac test in other qualitative tests for blood ?

A

green to blue colour at the zone of contact

23
Q

What is the principle of Guaiac test in other qualitative tests for blood ?

A

liberated oxygen from pseudoperoxidase activity of hemoglobin or myoglobin oxidizes the phenols present in guaiac to quinones

24
Q

what is the result for occult tablet test in other qualitative tests for blood ?

A

blue colour within 2 minutes

25
Q

What is the principle of Orthotoluidine test in other qualtitative tests for blood ?

A

prepare a urine sediment and add orthotoluidine and acid-peroxide mixture

26
Q

What is the result for orthotoluidine test in other qualitative tests for blood ?

A

greenish blue to deep blue colour that last for 1 minute or longer is a positive result

27
Q

The reagent pad for bilirubin is based on ___

A

the coupling reaction between bilirubin and the diazonium salt impregnated in the reagent pad in acid medium

28
Q

The ____ reaction of the bilirubin reagent pad produces a colour change ____

A

azocoupling

light tan to beige or pink

29
Q

What is the chemical equation for the bilirubin reagent pad reaction taking place ?

A

Blilirubin glucuronide + Ar - N+ ≡ N –(Acid)–> Azobilirubin

Aromatic compound + Diazonium salt —(Acid)–> Azo dye (brown)

30
Q

This brand uses 2,4-dichloroanilinediazonium salt for the bilirubin reagent pad

A

Multistix

31
Q

This brand uses 2,6-dichlorobenzine diazonium salt for the bilirubin reagent pad

A

Chemstrip

32
Q

This brand uses 2,4-dichlorobenzen diazonium tetrafluoroborate

A

vChem

33
Q

Which brand is the most sensitive when it comes to detecting bilirubin using a reagent strip ?

A

Multistix as it can detect as low as 0.4-0.8 mg/dL

34
Q

What may be the causes to a false-positive result for bilirubin reagent strip ?

A

drugs that can react directly with dizaonium salt (e.g. chlorpromazine and iodine metabolites)

drugs that result to a highly pigmented urine making the interpretation of the result difficult to read (e.g. phenazopyridine - colours the urine red)

Presence of indican (in intestinal disorders) also make the urine highly pigmented

35
Q

What may be the causes to a false-negative result for bilirubin reagent strip ?

A

improper specimen storage; specimen must be protected from light as it causes rapid oxidation of bilirubin to biliverdin or hydrolysis to free bilirubin

ascorbic acid 25 mg/dL; it can combin with the diazonium salt, preventing its reaction with bilirubin

high concentrations of nitrite

36
Q

What is the confirmatory test for bilirubin ?

A

Diazo Tablet Test (Icotest method)

37
Q

What is the range or bilirubin that can be detected by the icotest method ?

A

0.05-0.1 mg/dL

38
Q

What would be the result for a positive icotest ?

A

purple or blue colouration

39
Q

How many drops of urine are added onto the icotest special absorbent pad ?

A

10 drops of urine

40
Q

What is the principle of GMELIN’s test ?

A

in the presence of an acid, bilirubin undergoes varying degrees of oxidation

41
Q

What is the positive result for GMELIN’s test ?

A

green (biliverdin)
blue (bilicyanine)
yellow (choletelin)

42
Q

What is the principle of HARRISON’S SPOT test ?

A

Barium chloride + sulfate radicals + (in urine) = Barium sulfate (precipitate; bilirubin adheres to this)

Ferric chloride, in the presence of trichloroacetic acid = oxidizes bilirubin to biliverdin resulting to a colour change

43
Q

What is the positive result for HARRISON’S SPOT test ?

A

blue to green

44
Q

What is the principle of ROSENBACH’S MODIFICATION OF GMELIN’S TEST ?

A

drop of nitric acid containing yellow nitrous acid is applied to a filter paper soaked in urine

45
Q

What is the positive result of ROSENBACH’S MODIFICATION OF GMELIN’S TEST ?

A

band of coloured ring around the nitric acid

AUBF LAB (8 decks)

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