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MLS 415 Urinalysis & B.F. > Chemical Examination of Urine - Nitrite, Bilirubin, Urobilinogen, and Secondary Testing. > Flashcards

Chemical Examination of Urine - Nitrite, Bilirubin, Urobilinogen, and Secondary Testing. Flashcards

1
Q

What test results indicate a patient has a UTI?

A

Leukocyte and nitrite positive.

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2
Q

Some bacteria have the ability to reduce nitrite into:

A

Nitrate. They have an enzyme called nitrate reductase.

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3
Q

The nitrite test is a rapid screening test for?

A

The presence of bacteria or for a UTI.

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4
Q

Which type of UTI is more common and what type of bacteria is the usually cause?

A
  • Ascending infection.

- Gram negative rods.

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5
Q

What are the main bacteria responsible for UTI’s?

A
  • E. coli.
  • Proteus.
  • Enterobacter.
  • Klebsiella.
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6
Q

What causes a patient to have nitrates in their urine?

A

The presence of nitrate reductase producing bacteria. The longer the bacteria has been in the bladder, the more nitrates in the urine.

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7
Q

What is the principle reaction for a nitrite test?

A

Nitrites in an acidic pH will react with the aromatic amine forming a diazonium salt. The diazonium salt then reacts with the aromatic compound on the reagent pad, resulting in a color change from the azo dye being produced.

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8
Q

What is the specificity for a nitrites test?

A

Specific for nitrites.

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9
Q

What is the sensitivity of the chemstrip test for nitrites?

A

0.05 mg/dL.

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10
Q

What is the sensitivity of the multistix test for nitrites?

A

0.06 mg/dL.

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11
Q

What is the key amine reagent for nitrites on the chemstrip?

A

Sulfonamide

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12
Q

What is the key amine reagent for nitrites on the multistix?

A

P-arsanilic acid.

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13
Q

What is the key aromatic compound for nitrites?

A

Tetra-hydrobenzoquinolinol.

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14
Q

What causes a false positive nitrites test?

A
  • Pyridium.
  • Beets.
  • Improper storage.
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15
Q

What causes a false negative nitrites test?

A

Ascorbic acid levels > 25mg/dL.

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16
Q

What is the expected result for a nitrite test?

A

Negative

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17
Q

What are the reportable results for the nitrites?

A

Positive or negative.

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18
Q

Any positive amount of bilirubin found in the urine is significant because:

A
  • Early indicator of liver disease.

- Detectable before jaundice.

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19
Q

What are the 3 mechanisms of abnormal bilirubin metabolism?

A
  • Prehepatic.
  • Hepatic.
  • Posthepatic.
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20
Q

Excess breakdown of red blood cells:

A

Prehepatic.

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21
Q

Liver can not conjugate all of the bilirubin:

A

Hepatic.

22
Q

Conjugated bilirubin can’t make it to the intestine to become unconjugated:

A

Posthepatic.

23
Q

For prehepatic conditions, what are the expected results for uroblilinogen and bilirubin?

A
  • Urobilinogen: ↑↑.

- Bilirubin: negative.

24
Q

For hepatic conditions, what are the expected results for uroblilinogen and bilirubin?

A
  • Urobilinogen: Normal or ↑.

- Bilirubin: ↑.

25
Q

For posthepatic conditions, what are the expected results for uroblilinogen and bilirubin?

A
  • Urobilinogen: ↓↓.

- Bilirubin: ↑↑.

26
Q

What is the principle behind the bilirubin test?

A

Diazonium salt reacts with bilirubin glucuronide to produce a Azo dye.

27
Q

What are the key reagents for the bilirubin on a chemstrip?

A

Dicchlorobenzene diazonium tetrafluoroborate.

28
Q

What are the key reagents for the bilirubin on a multistix?

A

Dichlorobenzene diazonium salt.

29
Q

What can cause a false positive bilirubin test?

A

Pyridium

30
Q

What can cause a false negative bilirubin test?

A

Strong reducing substance.

31
Q

What is the sensitivity of the bilirubin test?

A

0.4 - 0.8 mg/dL.

32
Q

What are the limitations of the bilirubin test?

A

Photo oxidation.

33
Q

How is the bilirubin test reported?

A
  • Negative.

- Positive: small (+), moderate (++), large (+++).

34
Q

What does a urine sample look like if it is expected to be positive for bilirubin?

A

Amber with yellow foam.

35
Q

What type of bilirubin is being detected by the reagent strip?

A

Conjugated.

36
Q

What is the specimen of choice for urobilinogen is?

A
  • Right after a meal.

- During the “alkaline tide”.

37
Q

What is the principle of the urobilinogen multistix test?

A

Classic Ehrlich’s reaction: urobilinogen + p-dimethylaminobenzaldehyde in acid = a red color change.

38
Q

What is the principle of the urobilinogen chemstrip test?

A

Azocoupling reaction.

39
Q

What is the key reagent for the urobilinogen chemstrip test?

A

4- methoxybenzine-diaonium-fluoroborate.

40
Q

What is the key reagent for the urobilinogen multistix test?

A

Ehrlich’s reagent.

41
Q

What results are reportable for urobilinogen?

A
  • Ehrlich units or mg/dL. (1 mg = 1 EU).
  • 0.02, 1.0, 2.0, 4.0, >8.0.
  • Normal results are 0.2 or 1 mg/dL.
42
Q

What is the specificity for the urobilinogen test?

A
  • False positives from drugs and other substances.
  • Absences of urobilinogen cannot be measured.
  • Chemstrip is more specific for urobilinogen.
43
Q

What is the sensitivity for the urobilinogen test?

A

0.2 mg/dL.

44
Q

What are the limitations of the urobilinogen test?

A

Can only be reported in increments of 0.005.

45
Q

What if the confirmatory test for reducing sugars?

A

Clinitest

46
Q

What is the confirmatory test for bilirubin?

A

Ictotest

47
Q

What is the confirmatory test for ketones?

A

Acetest

48
Q

What is the confirmatory test for proteins?

A

Sulfosalycilic acid.

49
Q

What is the principle of the clinitest?

A
  • Reducing sugars convert cupric sulfate to corpus oxide.

- Color change fro blue- green- orange.

50
Q

What is the “pass through phenomenon”?

A

The test isn’t read at the exact time, the color would change fro blue- orange- green- back to blue.

51
Q

What were the uses of the clinitest?

A

Used for children under 2 with genetic disorders involving reducing sugars (galactosemia).

52
Q

What is the procedure of the acetest (nitroprusside tablet test)?

A

Drop specimen on tablet and a purple color indicates a positive test.
- Ignore other colors.

MLS 415 Urinalysis & B.F. (37 decks)

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