chemical examination of urine
DESCRIPTION
Chemical Examination of Urine. Ricki Otten MT(ASCP)SC [email protected]. Objectives:. Review the objectives on page 1 and 2 of the lecture handout Objectives marked with ‘*’ will not be tested over during student lab rotation. Historical Perspective: Urinalysis. - PowerPoint PPT PresentationTRANSCRIPT
![Page 2: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/2.jpg)
2
Objectives:
• Review the objectives on page 1 and 2 of the lecture handout
• Objectives marked with ‘*’ will not be tested over during student lab rotation
![Page 3: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/3.jpg)
3
Historical Perspective: Urinalysis• Physical examination of urine
– Odor– Taste– Color– Clarity
![Page 4: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/4.jpg)
4
Historical Perspective• Chemical examination of urine
– Limited reactions– Required large volumes of urine– Large volumes of reagent– Performed in test tubes– Time consuming and cumbersome– Clinical usefulness was not realized– Not routinely ordered
![Page 5: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/5.jpg)
5
Historical Perspective• Microscopic examination of urine
– Not until invention of the microscope– Then clinical usefulness realized
![Page 6: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/6.jpg)
6
Reagent Strip Testing
• Technology and necessity• Chemical reactions ‘miniaturized’• Required less urine• Test results within minutes• Easy to perform• Increased test utilization
Brunzel, 2nd Ed, page 124
![Page 7: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/7.jpg)
7
Reagent Strip Testing
• Ideal qualitative screening tool– Sensitive: Low concentration of substances
Negative result = normal
– Specific: Reacts with only one substance False negative and false positive
– Cost effective: Relatively inexpensive tool that provides information about the health statusof the patient
![Page 8: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/8.jpg)
8
Reagent Strip Testing• Chemically impregnated absorbent
pads attached to an inert plastic strip
• Each pad is a specific chemical reaction thattakes place upon contact with urine
• Chemical reaction causes the color of the pad tochange
• Color compared to a color chart for interpretation
![Page 9: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/9.jpg)
9
Reagent Strip Testing
• Qualitative or semi-quantitative results– Concentration units (mg/dl)– Negative, small, moderate large– Negative, 1+, 2+, 3+, 4+
• Timing of chemical reactions is CRITICAL– Shortest time requirement on one end of strip: 30 sec– Longest time requirement on the other: 2 min
![Page 10: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/10.jpg)
10
Reagent Strip Testing
• Principle of chemical reactions– False negative reactions– False positive reactions– Color interferences
• Alternative testing: used to confirm results that you may think are invalid due to– Interfering substance– Color interference (called color masking)
![Page 11: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/11.jpg)
11
Care and Storage (pg 4)
Confirmatory Testing (pg 6)
Reading assignment:
Textbook, chapter 7
Page 124-130
![Page 12: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/12.jpg)
12
Confirmatory Testing
• Alternative testing establishes the correctness or accuracy of another procedure
• Often used when urine is highly pigmented– Bilirubin reagent strip ictotest
![Page 13: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/13.jpg)
13
Confirmatory Testing
• Characteristics:– Differ in sensitivity
• Ictotest vs Bilirubin reagent strip
– Differ in specificity• SSA vs Protein reagent strip• Clinitest vs Glucose reagent strip
– Differ in methodology/reaction
Ideallywant all 3
![Page 14: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/14.jpg)
14
Differ in Specificity
• Clinitest reacts with all reducingsubstances
• Glucose reagent strip reacts with only one reducing substance: glucose
![Page 15: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/15.jpg)
15
10 reagent strip tests– Specific gravity– pH– Protein– Glucose– Ketones– Blood– Bilirubin– Urobilinogen– Nitrite– Leukocyte Esterase
• Purpose of the test• What is normal• What is abnormal• Reaction• Causes of invalid
results
![Page 16: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/16.jpg)
16
Specific Gravity: Purpose• Evaluates the concentrating and diluting
ability of the kidney– Density is related to the amount of
substances (solutes) in solution
– Increased density ~ increased solute in solution ~ hypertonic urine ~ concentrated urine
– Decreased density ~ decreased solute in solution ~ hypotonic urine ~ dilute urine
![Page 17: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/17.jpg)
17
Specific Gravity: Normal • Normal: 1.002 – 1.035
• Majority of urines: 1.010 – 1.025
• Physiologically impossible: 1.000>1.040
• Dependent upon hydration status
![Page 18: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/18.jpg)
18
Specific Gravity: Terms• Isosthenuria
– Fixed at 1.010– Renal tubules lost absorption and secreting capability
• Hypersthenuria– Increased specific gravity– Concentrated urine
• Hyposthenuria– Decreased specific gravity– Dilute urine
Sensitivity issues:Pregnancy testing
Urinary tract infection
![Page 19: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/19.jpg)
19
Specific Gravity: Methods
• Methods of measurement– Reagent strip test: indicates ionic solutes– Refractometer: indicates amount of total solutes
• Two functions of the kidney– Maintain water balance – Maintain electrolyte homeostasis
Performed by renal tubules through concentrating and diluting; reabsorbing and secreting water and electrolytes (ionic)
![Page 20: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/20.jpg)
20
Specific Gravity: Reaction • Based on a change in the pKa of a
polyelectrolyte on the reagent pad
• Increased ions in solution causes the polyelectrolyte on the pad to produce free H+
• Free H+ cause a change in pH on the reagent pad
• Change in pH: bromthymol blue indicator
![Page 21: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/21.jpg)
21
Specific Gravity: Reaction
![Page 22: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/22.jpg)
22
Specific Gravity
• Sensitivity: 1.000
• Specificity: detects only ionic substances– Radiographic dye– Mannitol– Glucose
Does not interfere
![Page 23: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/23.jpg)
23
pH: Purpose• Kidneys regulate body’s acid-base
balance by selective handling of H+ and HCO3-
– Urine pH reflects acid-base status of body
• Treatment protocol may require urine pH be maintained at a specific pH
(Aids in identification of crystals (microscope))
![Page 24: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/24.jpg)
24
pH: Normal
• Normal: ranges from 4.5 – 8.0
• First morning void: acidic
• Physiologically impossible: <4.5>8.0
1. Urine not handled properly
2. Old urine
3. Treatment induced
![Page 25: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/25.jpg)
25
pH: Interpretation
• Made in conjunction with – Acid-base status– Renal function – Presence of infection in urinary tract– Diet: high protein, low protein– Medications– Age of urine sample
![Page 26: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/26.jpg)
26
pH: Abnormal
• Acid– Respiratory acidosis– High protein diet– Starvation– UTI
• Alkaline– Respiratory alkalosis– Vegetarian diet– Renal tubular acidosis– UTI
![Page 27: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/27.jpg)
27
pH: Reaction
• Double indicator system– Methyl red– Bromthymol blue
• Amount of free H+ influences acidity of urine and cause pH indicator to change color
Needed to measure the wide pH range: acid to alkaline
![Page 28: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/28.jpg)
28
pH:
• Invalid test results due to:– Improper handling of urine sample
– Contamination of urine vessel prior to collection
– ‘Run-over’ phenomenon
![Page 29: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/29.jpg)
29
Protein: Purpose• Normal kidneys secrete LITTLE protein
<15 mg/dl (or <150 mg/24 hours)
• The protein that is found in urine comes from– Bloodstream– Urinary tract
• Proteinuria is an indicator of early renal disease
• Proteinuria also caused by non-renal disease
![Page 30: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/30.jpg)
30
Renal Cause of Proteinuria: • Glomerular damage:
– Most serious cause of proteinuria– Most common cause of proteinuria– Glomerulonephritis– Nephrotic Syndrome
• Tubular dysfunction:– Reabsorption capability decreased– Toxin exposure, inherited disorder– Fancon’s syndrome: heavy metal poisoning
![Page 31: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/31.jpg)
31
Classification of Proteinuria
• Functional• Orthostatic (postural)• Transient• Pathologic
– Pre-renal (overflow)– Renal: glomerular– Renal: tubular– Post-renal
![Page 32: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/32.jpg)
32
Protein: Methods
• Reagent strip test• SSA test• Foam test• Micro-albumin test
![Page 33: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/33.jpg)
33
Protein: Reagent Strip
• The reagent pad is held at a constant pH of 3 by a buffer
• Proteins (anions) in solution cause anindicator dye to release H+ causing a colorchange
• ‘Protein error of indicators’
![Page 34: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/34.jpg)
34
Protein: Reagent Strip• Sensitivity: ~ 10-25 mg/dl• Specificity: reacts with albumin
– False positive: highly alkaline urine (pH > 8.0)– False negative:
Dilute urine Presence of other proteins
(Tamm-Horsfall, globulins, myoglobin,
free light chains, hemoglobin)
![Page 35: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/35.jpg)
35
Protein: SSA (Exton’s Test)
• Sulfosalicylic Acid (SSA) Precipitation Test
• Acid will precipitate proteins out of solution causing the solution to become cloudy
• Amount of cloudiness is related to the amount of protein present
![Page 36: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/36.jpg)
36
Protein: SSA (Exton’s Test)
• Amount of cloudiness is evaluated, thus must use centrifuged urine
• Sensitivity: 5-10 mg/dl• Specificity: detects all protein
![Page 37: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/37.jpg)
37
Protein: SSA (Exton’s Test)
• False positive results: – Radiographic dyes– Turbid urine– Uncentrifuged urine
• False negative results:– Highly alkaline urine– Dilute urine
![Page 38: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/38.jpg)
38
Protein: Foam test
• Shake aliquot of urine and observe color of resulting foam
• White foam: protein present
![Page 39: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/39.jpg)
39
Protein: Micro-albumin test
• Measures very low concentration of albumin (better sensitivity than reagent strip test for albumin)
• Management of diabetic patient
• Methods vary: reagent strip test,immunochemical reaction
![Page 40: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/40.jpg)
40
Glucose: Purpose• Healthy normal urine does not contain
glucose
• Normally, glucose is filtered by the glomerulus and is reabsorbed back into the bloodstream through active transport mechanism
• Glucose in urine is pathologic
![Page 41: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/41.jpg)
41
Glucose: Purpose• Glucosuria
Glycosuria
• Caused by renal and non-renal disease– Pre-renal glycosuria: plasma glucose level
exceeds renal threshold (diabetes mellitus)
– Renal glycosuria: plasma glucose level below renal threshold, but tubules cannot reabsorb glucose back into bloodstream
Terms used interchangeably
![Page 42: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/42.jpg)
42
Reducing Substances: Purpose• Reducing Substances:
– Glucose– Other sugars: galactosemia (inherited
metabolic disorder)
![Page 43: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/43.jpg)
43
Glucose, Reducing Substances
• Normal: negative• Abnormal:
– Diabetes mellitus: glucose– Impaired renal tubular reabsorption: glucose
– Inborn error of metabolism: galactosemia
![Page 44: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/44.jpg)
44
Methods
• Reagent strip: detects only glucose
• Copper Reduction: detects reducing substances
![Page 45: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/45.jpg)
45
Glucose: Reagent Strip
• Detects only glucose• Double sequential enzyme reaction
![Page 46: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/46.jpg)
46
Glucose: Reagent Strip
• Sensitivity: ~ 30 mg/dl• Specificity:
– Reacts only with glucose– False positive:
• Strong oxidizing agents (bleach)• Peroxides
– False negative: • Ascorbic acid (reducing agent)• Improperly stored urine: glycolysis
![Page 47: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/47.jpg)
47
Clinitest Reaction
• Copper Reduction Test:– Reducing substances are able to reduce
copper sulfate to cuprous oxide
– Pass-through phenomenon
– All children <2 years: metabolic disorder(galactosemia)
![Page 48: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/48.jpg)
48
Clinitest Reaction
• Sensitivity: ~ 250 mg/dl• Specificity:
– Reacts with all reducing substances– Reducing sugars: glucose, galactose,
fructose, lactose, maltose (NOT SUCROSE)
– False positive: any reducing substance(Ascorbic acid)
– False negative: radiographic dye
![Page 49: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/49.jpg)
49
Ketones: Purpose
• Ketones are intermediary products of fat metabolism
![Page 50: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/50.jpg)
50
Ketones
• Three ketone bodies– Acetone 2%– Acetoacetic acid 20%– Beta-hydroxybutyric acid 78%
• Characteristic ‘fruity breath’ ~ acetone
![Page 51: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/51.jpg)
51
Ketones: Normal
• Normal: negative
• Abnormal:– Inability to utilize carbohydrates– Excessive loss of carbohydrates– Inadequate intake of carbohydrates
![Page 52: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/52.jpg)
52
Ketones: Methods
• Reagent strip
• Acetest: tablet test
![Page 53: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/53.jpg)
53
Ketones: Method
• Glycine: also measures acetone– Reagent strip: check package insert– Acetest tablets: contain glycine
![Page 54: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/54.jpg)
54
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
![Page 55: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/55.jpg)
55
Blood: Purpose
• Blood in urine indicates pathology
• Two forms found in urine– Intact RBC– Hemolyzed RBC
![Page 56: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/56.jpg)
56
Blood: Terms
• Hematuria
• Hemoglobinuria
• Myoglobinuria
All will give a positive blood reaction
![Page 57: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/57.jpg)
57
Blood: Reagent strip
• Test can detect hemolyzed RBC
• Heme moiety imparts peroxidase activity and catalyzes the reaction
![Page 58: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/58.jpg)
58
Blood
• Sensitivity• Specificity
– Intact RBC– Hemolyzed RBC (hemoglobin)– Myoglobin
– False positives: myoglobin, oxidizing agents– False negatives: ascorbic acid
![Page 59: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/59.jpg)
59
Blood:
• Correlate reagent strip results– Microscopic findings– Color and clarity
![Page 60: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/60.jpg)
60
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
![Page 61: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/61.jpg)
61
Three mechanisms
• Pre-hepatic: liver is healthy
• Hepatic: liver disease
• Post-hepatic: liver is healthy, obstruction indicated
![Page 62: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/62.jpg)
62
Bilirubin: Methods
• Reagent strip• Ictotest: tablet test• Foam test
![Page 63: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/63.jpg)
63
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
![Page 64: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/64.jpg)
64
Bilirubin: Methods
• Reagent strip• Ictotest: tablet test
• Sensitivity differsReagent strip: ~0.5 mg/dlIctotest: 0.05 – 0.1 mg/dl
![Page 65: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/65.jpg)
65
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
![Page 66: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/66.jpg)
66
Bilirubin: Foam Test
• Shake urine and observe resulting foam• Yellow foam = bilirubin
![Page 67: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/67.jpg)
67
Urobilinogen: Methods
• Reagent strip test– Two reactions dependent upon manufacturer
• Para-dimethylaminobenzaldehyde• Diazonium salt
– Cannot determine absence of UBG
• Watson-Schwartz assay
![Page 68: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/68.jpg)
68
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
![Page 69: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/69.jpg)
69
Urobilinogen: Watson Schwartz
• Classic method used to differentiateurobilinogen from porphobilinogen using adifferential extraction method
• Para-dimethylaminobenzaldehyde
![Page 70: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/70.jpg)
70
Nitrite: Purpose
• Bacteria that contain a specific enzyme can reduce dietary nitrates to nitrites
• Rapid screening test for UTI
![Page 71: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/71.jpg)
71
Nitrite: Normal
• Normal: negative
• Abnormal:– Cystitis: bladder– Pyelonephritis: kidney
![Page 72: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/72.jpg)
72
Nitrite: Method• Reagent strip test
Nitrite + aromatic amine diazonium saltDiazonium salt + aromatic compound pink color
• Sensitivity: 0.06-0.1 mg/dl nitrite~ 10,000 organisms
![Page 73: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/73.jpg)
73
Nitrite: Method• Reagent strip test
Specificity:– False positive: improper specimen handling; color
masking– False negative: bacteria cannot reduce nitrates
Bladder time not sufficient: need 4 hoursLow nitrite levelsAscorbic acidAntibiotic inhibition of bacteriaFurther reduction of nitrites to nitrogen
![Page 74: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/74.jpg)
74
Leukocyte Esterase: Purpose
• Increased WBC in urine is pathologic– Indicates inflammation, infection
• Neutrophils most common type of WBC found in urine
• Can detect intact WBC and lysed WBC
![Page 75: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/75.jpg)
75
Leukocyte Esterase: Normal
• Normal: negative
• Abnormal:– Bacterial infection:
cystitis, pyelonephritis, urethritis– Non-bacterial infection: yeast, trichomonas
![Page 76: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/76.jpg)
76
Leukocyte Esterase: Method
• Reagent strip: Granules in cytoplasm of WBC contain an enzyme (esterase)
Ester –esterase aromatic compoundAromatic compound + diazonium salt Purple colored complex
![Page 77: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/77.jpg)
77
Leukocyte Esterase
• Sensitivity: 5-15 WBC/hpf
• Specificity:– False positive: vaginal contamination; color
masking– False negative: strong oxidizing agents
(bleach); lymphocytes (no granules)
![Page 78: Chemical Examination of Urine](https://reader030.vdocument.in/reader030/viewer/2022012823/56815d71550346895dcb7a46/html5/thumbnails/78.jpg)
78