Nitrite Testing in Urine for UTIs

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Questions and Answers

What is the primary process that the nitrite test relies on?

  • Conversion of creatinine to urea
  • Conversion of nitrate to nitrite by bacterial action (correct)
  • Conversion of glucose to pyruvate
  • Conversion of protein to amino acids

Why is a first morning urine specimen preferred for the nitrite test?

  • It is less likely to be contaminated
  • It has a higher pH level
  • It allows overnight bladder incubation for bacterial action (correct)
  • It contains the highest concentration of glucose

What indicates a positive result in a nitrite test?

  • The specimen is cloudy
  • The presence of pink azo dye (correct)
  • The pH level is above 7
  • No bacterial growth is observed

What can lead to a false positive result in the nitrite test?

<p>Improper specimen storage after collection (B)</p> Signup and view all the answers

Which reagent strip contains p-arsanilic acid for nitrite testing?

<p>Multistix (D)</p> Signup and view all the answers

What is the detection threshold for nitrite in the Multistix test?

<p>0.075 mg per deciliter (D)</p> Signup and view all the answers

How long does the Chemstrip test take to produce a result?

<p>30 seconds (B)</p> Signup and view all the answers

What should be interpreted as a negative result in the nitrite test?

<p>Formation of pink spots or edges (C)</p> Signup and view all the answers

What does the Chemstrip contain to react with nitrite?

<p>Benzoquinoline and sulfanilamide (A)</p> Signup and view all the answers

What is the minimum duration required for bladder incubation for effective nitrite testing?

<p>4 hours (D)</p> Signup and view all the answers

Flashcards

Nitrate Reduction

The ability of certain bacteria to convert nitrate (NO3-) into nitrite (NO2-) in the urine.

First Morning Urine Sample

A urine sample collected first thing in the morning, after a period of sleep, the bladder has incubated for several hours, providing an optimal environment for bacteria to convert nitrates.

Positive Nitrite Test

A positive nitrite test indicates the likely presence of a urinary tract infection (UTI) caused by bacteria that produce nitrite.

Nitrite Reagent Strip

Impregnated with a chemical that reacts with nitrite in urine, producing a pink azo dye, indicating a positive result.

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p-arsanilic acid

A chemical that interacts with nitrite to form a pink azo dye, used in the nitrite reagent strip.

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Benzoquinoline

The chemical that reacts with the activated reagent (diazonium salt) to create the pink azo dye in the nitrite test.

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Nitrite Sensitivity

The minimum amount of nitrite detectable by the test, signifying a positive result.

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Sulfanilamide

A chemical that interacts with nitrite to produce a pink azo dye.

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Pink Spots or Edges (Nitrite Test)

A pink spot or edge on a nitrite reagent strip is considered a negative result, indicating absence of nitrates.

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Contaminated Urine Sample (Nitrite Test)

A urine sample that has been improperly stored, allowing for the growth of contaminating bacteria, which may lead to a false positive nitrite test

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Study Notes

Nitrite Testing in Urine

  • Mechanism: The test relies on bacteria converting nitrate to nitrite in urine.
  • Specimen Collection: A first morning specimen is ideal, as overnight bladder incubation (at least 4 hours) is needed for bacterial conversion.
  • Positive Result: A positive result suggests a urinary tract infection (UTI) and warrants further culture testing. However, contamination after collection can also yield a positive result.
  • Reagent Strips:
    • Multistix: Uses p-arsanilic acid, which reacts with nitrite to create a diazonium salt, then couples with benzoquinoline to form a pink azo dye. Detects 0.075 mg/dL nitrite at 40 seconds.
    • Chemstrip: Contains benzoquinoline and sulfanilamide, which react with nitrite to form a pink azo dye at 30 seconds. Detects 0.05 mg/dL nitrite.
  • Interpretation Note: Pink spots or edges on the reagent strips are considered negative results.

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