Chemical Examination of Urine Part III: Ketones, Blood, Bilirubin

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Chemical Examination of UrinePart IIIKetones,
Blood, Bilirubin Urobilinogen

• Ricki Otten MT(ASCP)SC
• uotten_at_unmc.edu

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Ketones Purpose

• Ketones are intermediary products of fat
  metabolism

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Ketones

• Three ketone bodies
• Acetone 2
• Acetoacetic acid 20
• Beta-hydroxybutyric acid 78
• Characteristic fruity breath acetone

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Ketones Normal

• Normal negative
• Abnormal
• Inability to utilize carbohydrates
• Excessive loss of carbohydrates
• Inadequate intake of carbohydrates

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Ketones Methods

• Reagent strip
• Acetest tablet test

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Ketones Method

• Glycine also measures acetone
• Reagent strip check package insert
• Acetest tablets contain glycine

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Ketones

• Reagent strip
• Sensitivity 5-10 mg/dl
• Specificity acetoacetic acid and/or acetone
• False positive highly pigmented urine
• False negative improper specimen handling
• Acetest
• Specificity acetoacetic acid and acetone
• False positive highly pigmented urien
• False negative improper specimen handling

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Blood Purpose

• Blood in urine indicates pathology
• Two forms found in urine
• Intact RBC
• Hemolyzed RBC

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Blood Terms

• Hematuria
• Hemoglobinuria
• Myoglobinuria

All will give a positive blood reaction
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Blood Reagent strip

• Test can detect hemolyzed RBC
• Heme moiety imparts peroxidase activity and
  catalyzes the reaction

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Blood

• Sensitivity
• Specificity
• Intact RBC
• Hemolyzed RBC (hemoglobin)
• Myoglobin
• False positives myoglobin, oxidizing agents
• False negatives ascorbic acid

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Blood

• Correlate reagent strip results
• Microscopic findings
• Color and clarity

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Bilirubin and Urobilinogen

• Bilirubin in urine is always pathologic
• liver disease
• Urobilinogen in urine normal to have a small
  amount
• 0.2 1.0 mg/dl

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Three mechanisms

• Pre-hepatic liver is healthy
• Hepatic liver disease
• Post-hepatic liver is healthy, obstruction
  indicated

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Bilirubin Methods

• Reagent strip
• Ictotest tablet test
• Foam test

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Bilirubin Methods

• Reagent strip
• Ictotest tablet test
• Same reaction
• Same specificity conjugated bilirubin
• False positive urine color
• False negative low concentration, ascorbic acid,
  improper specimen handling

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Bilirubin Methods

• Reagent strip
• Ictotest tablet test
• Sensitivity differs
• Reagent strip 0.5 mg/dl
• Ictotest 0.05 0.1 mg/dl

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Bilirubin Methods

• Possible to have a negative reagent strip test
  and positive ictotest
• Difference in sensitivity levels
• Always perform Ictotest when
• Urine bilirubin test specifically ordered
• Urine appearance is amber even if bilirubin
• reagent strip test is negative
• Positive reagent strip test

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Bilirubin Foam Test

• Shake urine and observe resulting foam
• Yellow foam bilirubin

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Urobilinogen Methods

• Reagent strip test
• Two reactions dependent upon manufacturer
• Para-dimethylaminobenzaldehyde
• Diazonium salt
• Cannot determine absence of UBG
• Watson-Schwartz assay

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Urobilinogen Methods

• Para-dimethylaminobenzaldehyde
• Sensitivity 0.2 mg/dl
• Specificity
• False positive any Ehrlich reactive compound
  color masking urine at body temp
• False negative improper specimen handling
• Diazonium salt
• Sensitivity 0.4 mg/dl
• Specificity reacts only with UBG
• False positive color masking
• False negative improper specimen handling

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Urobilinogen Watson Schwartz

• Classic method used to differentiate
• urobilinogen from porphobilinogen using a
• differential extraction method
• Para-dimethylaminobenzaldehyde