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

Chemical Examination of Urine Part III: Ketones, Blood, Bilirubin & Urobilinogen. Ricki Otten MT(ASCP)SC uotten@unmc.edu. Ketones are intermediary products of fat metabolism. Ketones: Purpose. Ketones. Three ketone bodies Acetone 2% Acetoacetic acid 20% Beta-hydroxybutyric acid 78%

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

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  1. Chemical Examination of UrinePart III:Ketones, Blood, Bilirubin &Urobilinogen Ricki Otten MT(ASCP)SC uotten@unmc.edu

  2. Ketones are intermediary products of fat metabolism Ketones: Purpose

  3. Ketones • Three ketone bodies • Acetone 2% • Acetoacetic acid 20% • Beta-hydroxybutyric acid 78% • Characteristic ‘fruity breath’ ~ acetone

  4. Ketones: Normal • Normal: negative • Abnormal: • Inability to utilize carbohydrates • Excessive loss of carbohydrates • Inadequate intake of carbohydrates

  5. Ketones: Methods • Reagent strip • Acetest: tablet test

  6. Ketones: Method • Glycine: also measures acetone • Reagent strip: check package insert • Acetest tablets: contain glycine

  7. 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

  8. Blood: Purpose • Blood in urine indicates pathology • Two forms found in urine • Intact RBC • Hemolyzed RBC

  9. Blood: Terms • Hematuria • Hemoglobinuria • Myoglobinuria All will give a positive blood reaction

  10. Blood: Reagent strip • Test can detect hemolyzed RBC • Heme moiety imparts peroxidase activity and catalyzes the reaction

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

  12. Blood: • Correlate reagent strip results • Microscopic findings • Color and clarity

  13. Bilirubin in urine is always pathologic: liver disease Urobilinogen in urine: normal to have a small amount: 0.2 – 1.0 mg/dl Bilirubin and Urobilinogen

  14. Three mechanisms • Pre-hepatic: liver is healthy • Hepatic: liver disease • Post-hepatic: liver is healthy, obstruction indicated

  15. Bilirubin: Methods • Reagent strip • Ictotest: tablet test • Foam test

  16. 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

  17. Bilirubin: Methods • Reagent strip • Ictotest: tablet test • Sensitivity differs Reagent strip: ~0.5 mg/dl Ictotest: 0.05 – 0.1 mg/dl

  18. 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

  19. Bilirubin: Foam Test • Shake urine and observe resulting foam • Yellow foam = bilirubin

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

  21. 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

  22. Urobilinogen: Watson Schwartz • Classic method used to differentiate urobilinogen from porphobilinogen using a differential extraction method • Para-dimethylaminobenzaldehyde

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