week 8: chemical ua sensitivity and specificity test principles reagent strip tests back-up...
TRANSCRIPT
![Page 1: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/1.jpg)
Week 8: Chemical UA
• Sensitivity and specificity
• Test principles
• Reagent strip tests
• Back-up confirmatory tests
• Interfering substances: false positives and negatives
![Page 2: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/2.jpg)
Urine Chemistries
![Page 3: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/3.jpg)
![Page 4: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/4.jpg)
Test Performance
• Sensitivity: minimum concentration
• Specificity: discrimination
• Interference factors
![Page 5: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/5.jpg)
![Page 6: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/6.jpg)
![Page 7: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/7.jpg)
pH
• Normal: 4 - 8 (mean 6)
• Control blood pH
• Principle: Methyl red and Bromthymol blue double indicator method
• Report to nearest 0.5 pH unit
• Help identify crystals
![Page 8: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/8.jpg)
![Page 9: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/9.jpg)
![Page 10: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/10.jpg)
Protein
• Normal: negative• Sensitive indicator of renal diseases
• Glomerulonephritis• Pyelonephritis
• Malignant hypertension• Preeclampsia• Severe exercise• Principle: Protein error of pH indicator
• Tetrabromphenyl blue buffered at pH 3.2
• Watch for false positive in alkaline urine
![Page 11: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/11.jpg)
![Page 12: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/12.jpg)
Back-Ups for Protein
• 3% sulfosalicylic acid (SSA)• 0 to 4+ depending
on precipitation
• Trichloroacetic (TCA) acid
• Heat and acetic acid
![Page 13: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/13.jpg)
Microalbuminuria
• > 20 mg/L (30-300 mg/day) albumin in urine• Not detectable with reagent strip (6-15 mg/dL) or
SSA (5 mg/dL)• Predictive of nephropathy and eventual renal
failure in patients with type I diabetes mellitus• Detect patients with increased risk of renal and
cardiovascular disease, associated with insulin resistance and endothelial dysfunction
• Albumin to creatinine ratio corrects for hydration level
![Page 14: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/14.jpg)
Glucose
• Normal: negative• Blood threshold for glucose 175 mg%• Elevated with diabetes (hyperglycemia)• Principle: Glucose oxidase and hexokinase
Glu Glu Ox > Gluconic acid + H2O2
H2O2 + o-tolidine Perosidase > color
• Specific for glucose• Sensitive to redox agents
![Page 15: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/15.jpg)
![Page 16: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/16.jpg)
Back-Ups for Glucose
• Lily TesTape• Specific to glucose
• Clinitest (Benedict’s)• Non-specific for any
• reducing agents
• Cupper sulfate reduction
• Cu++ (blue) + Glu ——> CuO (yellow-red)
![Page 17: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/17.jpg)
Ketone Bodies
• Normal: negative• Elevated with diabetic ketoacidosis,
starvation• Most sensitive to acetoacetate, less sensitive
to acetone, not sensitive to -hydroxy butyrate
• Principle: Sodium nitroprusside Legal’s test• Some have glycine to increase sensitivity to
acetone
![Page 18: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/18.jpg)
![Page 19: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/19.jpg)
Back-Ups for Ketone
• Acetest table test• Same principle as
reagent strip
• Gerhardt’s• FeCl3 non-specific test
![Page 20: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/20.jpg)
Urobilinogen
• Normal: up to 1 Ehrlich unit/dL (not negative)
• Negative in complete obstruction of common bile duct
• Elevated in liver disease and hemolytic anemia
• Principle: p-dimethylaminobenzaldehyde, azocoupling in acid to form pink azo dye
![Page 21: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/21.jpg)
![Page 22: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/22.jpg)
![Page 23: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/23.jpg)
Back-Up for Urobilinogen
• Watson-Schwartz• Extraction with chloroform and butanol
• Not commonly done
![Page 24: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/24.jpg)
Bilirubin
• Normal: negative• Liver disease
• Viral hepatitis• Cirrhosis
• Obstructive jaundice• Bile stone in common bile duct• Pancreatic cancer
• Principle: Diazonium salt reaction, azo coupling in acid to form purple azo dye
![Page 25: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/25.jpg)
![Page 26: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/26.jpg)
Back-Ups for Bilirubin
• Ictotest• Same principle as
reagent strip
• Harrison’s spot test• Fouchet’s reagent (TCA)
![Page 27: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/27.jpg)
Blood
• Normal: negative
• Hematuria, hemoglobinuria, myoglobinuria
• Principle: Hb used as catalyst for o-tolidine or benzidine oxidation (pseudo-peroxidase activity)
• If hematuria, should see red cells
• Menstrual contamination
• Bacterial peroxidase can cause false positive
![Page 28: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/28.jpg)
![Page 29: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/29.jpg)
Nitrite
• Some bacteria reduce nitrate to nitrite
• Diazotization with aromatic amine like p-arsanilic acid or sulfanilamide
![Page 30: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/30.jpg)
Leukocyte Esterase
• Leukocyte (neutrophil) esterase cleave an ester which is azocoupled with aromatic amine
• Correlate with microscopic WBC
![Page 31: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/31.jpg)
Specific Gravity
• Measure ionic solute
• As protons are released from polyelectrolytes, pH decreases that change bromthymol blue indicator
![Page 32: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/32.jpg)
Ascorbic Acid
• Ascorbic acid reduces a dye causing color change
• 2,6-dichlorophenolinedophenol
![Page 33: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/33.jpg)
Quality Control and Quality Assurance
![Page 34: Week 8: Chemical UA Sensitivity and specificity Test principles Reagent strip tests Back-up confirmatory tests Interfering substances: false positives](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649cd95503460f949a3865/html5/thumbnails/34.jpg)
Homework
• Construct a table tests: stix and back ups
Test Principle Sens Spec False Pos False Neg