university of nebraska medical center objectives: on completion of
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CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 1
Routine Urinalysis- Physical and Chemical Examination
f U i
University of Nebraska Medical Center
of Urine
CLS 500: Application and Interpretation of Clinical Laboratory Data
Objectives: On completion of this unit, participants will be able to:
• Describe considerations on collection, handling, and processing of urine specimens
• Identify screening tests for physical andIdentify screening tests for physical and chemical examination of urine
• Describe major sources of error in routine urinalysis procedures
• Define common terms applied to urinalysis and renal disease 2
Objectives (continued)• Correlate physical & chemical tests of
urine in:– Cystitis
– Pyelonephritis
– Renal glycosuria
– Diabetes mellitus
– Diabetes insipidus
– Hepatic, obstructive or hemolytic jaundice
– Acute and chronic glomerulonephritis
– Nephrotic syndrome3
Objectives (continued)
• Explain the significance of the following:– Pos Clinitest and neg dipstick for glucose– Pos dipstick for glucose and neg Clinitest– False positive dipstick for proteinp p p– False negative for ketones– False negative for bilirubin– Neg bilirubin dipstick and pos Ictotest– Pos bilirubin and neg urobilinogen– Neg bilirubin and pos urobilinogen
4
Objectives (continued)
• Predict the potential changes that may take place in a urine specimen that remains at room temperature for longer than 2 hours
5
What is Urine?• A fluid which is continuously formed
in and excreted from the body
• Composed of water and
metabolic waste productsmetabolic waste products
• An actual fluid biopsy of the kidney– kidney is the only organ with such a noninvasive means
by which to evaluate its status
6
CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 2
Functions of the Kidney
• Produces urine
• Maintains electrolyte balance
• Maintains blood pH
• Produces hormones
• Excretes waste
7
The Purpose of Urinalysis?
• To aid in the diagnosis of disease
• To monitor wellness (screening for asymptomatic, congenital, or hereditary disease))
• To monitor the progress of disease
• To monitor therapy (effectiveness or complications)
A Complete Urinalysis Providesa Fountain of Information
pancreas muscle
intoxication
acid base equilibrium inborn errors of metabolismwater status
cardiovascular system
blood carbohydrate metabolism
9
bonekidney
drug abuse
pregnancy
liver
hormones
infection
respiratory system
fat metabolism
protein metabolism
urinary tract
gastrointestinal tract
nutritionelectrolytes
central nervous system
Types of Urine Specimens• Random• First morning• Midstream clean catch• Fasting• Catheterized• Suprapubic aspiration• Pediatric specimen• Timed collections (for quantitative testing)
– 2-hour postprandial– 24-hour, 12-hour, 6-hour 10
General Considerations
• Use clean, dry, disposable, sterile container
• Label properly
• ANALYZE WITHIN ONE HOUR
• Preserve urine constituents– Refrigeration (2-8C)
– Advantages vs disadvantages11
Changes at Room Temperature
• Increased pH• Decreased glucose• Decreased ketones• Decreased bilirubin• Decreased urobilinogen• Increased bacteria• Increased turbidity• Disintegration of red blood cells and casts• Changes color
12
CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 3
Collection Errors
• Labeling (label the container, not lid)– Patient name
– Patient identification number (MRN, DOB)
– Date of collectionDate of collection
– Time of collection
– Test ordered
– Name of ordering physician/clinician
• Delay in testing– Testing after one hour
– Lack of refrigeration 13
Historical Perspective: Urinalysis• Physical examination
of urine– Odor
– Taste
14
– Color
– Clarity
– Volume
Historical Perspective
• Chemical examination of urine– Limited reactions/large volumes required
– Time consuming/cumbersome
– Clinical usefulness was not realized
15
Clinical usefulness was not realized
– Not routinely ordered
• Microscopic exam of urine– Clinical usefulness not
realized until invention of
the microscope
Reagent Strip Testing
• Technology and necessity
• Chemical reactions ‘miniaturized’
• Required less urine
U i t ll t
16
• Urine easy to collect
• Test results within minutes
• Easy to perform
• Increased test utilization
Brunzel, 2nd Ed, page 124
Reagent Strip Testing
• Ideal qualitative screening tool– Sensitive: Low concentration of substances
Negative result = normal
17
– Specific: Reacts with only one substanceFalse negative and false positive
– Cost effective: Relatively inexpensive tool that provides information about the health status of the patient
Complete Urinalysis
• Physical Examination– Color, Clarity, Concentration
– Odor, Volume
C• Chemical Examination– 10 chemical reactions
• Microscopic Examination
18
CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 4
Physical Examination of Urine
Color, Clarity, Foam,
Concentration, Odor, Volume
Physical Properties
• Volume– Average: 1200 to 1500 ml/24 hours
– ‘Extremes’: 600-2,000 ml/24 hrs
• TermsTerms– Anuria -no urine output
– Polyuria -increased urine output
– Oliguria -decreased urine output
– Nocturia -excessive output at night
– Dysuria -painful urination20
Color
BrownHemoglobin
BluePseudomonas infection
Red Green
ColorlessDilute Urine
YellowNormal
OrangePyridium
AmberBilirubin
Blood
Bright YellowVitamins
Medication
Dark GreenBiliverdin
21
Clarity / Appearance
ClearLike water; easily read newsprint
CloudyLines are barely visible; cannot read newsprint
HazyBlurry but
lines are still visible
TurbidCannot see through it; often have particulates
22
What Can Cause Urine to be Hazy, Cloudy, or Turbid?
Epithelial
Cells
White Blood
Red
Blood
Amorphous
MaterialCells Blood Cells
Blood Cells
Material
Sperm Fat Mucus Yeast
Bacteria Powder Casts Crystals
23
Foam
• White foam– protein is
presentpresent
• Yellow foam – bilirubin is
present
CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 5
Concentration
• Concentration is determined by the specific gravity test
• 2 ways specific gravity can be determinedR f t t– Refractometer
– Reagent Strip• Most labs use this method
• Increased glucose and protein levels do not interfere
25
Odor• Faintly aromatic
– Normal
• Ammonia – Old urine
• Pungent– UTIU
• Fruity, Sweet– Ketones
• Mousy, Barny– PKU disease
• Maple syrup– Maple syrup urine
disease 26
Taste – thank goodness we don’t do this anymore!!
This doesn’t taste like lemonade!!!
Chemical Examination of Urine
Reagent Strip Testing
Reagent Strip Testing• Chemically impregnated absorbent
pads attached to an inert plastic strip
• Each pad is a specific chemical reaction that
29
takes place upon contact with urine
• Chemical reaction causes the color of the pad to
change: reaction is timed
• Color compared to a color chart for interpretation
Reagent Strip Proper Storage
• Tightly closed container
• Cool dry place
• Avoid volatile fumes
• Expiration date
• Do not use if pads are discolored
• Do not touch pads
• Run positive and negative controls once/day30
CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 6
Quality Control• Ensures reliability of results
• Evaluates reagent strip
• Run 2 controls once a day
• Positive control
N ti t l
31
• Negative control
• BOTH controls MUST be ‘ok’ else patient testing cannot be performed
The Dipstick Procedure
• Wear gown & gloves
• Mix the urine
• Insert reagent stripg p
• Remove excess urine
• Time the reactions
• Compare test areas to color chart
• Record results
32
The Urine Dipstick10 Reactions on 1 Plastic Strip
• Glucose• Bilirubin• Ketones• Specific gravity
• Purpose of the test
• What is normal
• What is abnormal• Specific gravity• Blood• pH• Protein• Urobilinogen• Nitrites• Leukocytes
33
• Causes of abnormal results
• Causes of false pos/neg results
Glucose
• All glucose is normally reabsorbed in the tubules unless the blood level is higher than the renalunless the blood level is higher than the renal threshold (160 to 180 mg/dl)
• Normal = Negative
• Abnormal = Diabetes mellitusImpaired tubular reabsorptionInborn errors of metabolism
34
Glucose
• Glucosuria
Glycosuria
• Caused by renal and non renal disease
Terms used interchangeably
35
• 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
Glucose• Sensitivity: ~ 100 mg/dl
• Specificity: – Reacts only with glucose
– False positive:
36
False positive: • Strong oxidizing agents (bleach)
• Peroxides
– False negative: • Ascorbic acid (reducing agent)
• High ketone levels
• Improperly stored urine: glycolysis
CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 7
Clinitest (tablet test)
• Is a copper reduction test (cupric to cuprous)
• Detects all reducing sugars
• Reacts with glucose, galactose, lactose, fructose, ascorbic acid, homogentisic acid; , , g ;not sucrose
• All children <2 years: screened for metabolic disorder (galactosemia)
37
• Clinitest is non-specific– Reacts with all reducing substances
• Clinitest not as sensitiveWill d t t l t 250 /dl
Glucose Dipstick vs Clinitest
38
– Will detect glucose at 250 mg/dl
• Dipstick is specific for glucose (enzyme rxn)
• Dipstick more sensitive– Will detect glucose at 100 mg/dl
Bilirubin
• Bilirubin is formed from the breakdown of hemoglobin in the reticuloendothelial (RE) g ( )system
• Only conjugated bilirubin is found in urine
• Normal = Negative
• Abnormal = Liver disease-hepatic jaundiceObstruction-obstructive jaundice39 40
Bilirubin• False Negative
– Ascorbic acid inhibits
– High urine nitrites inhibit
– Low bilirubin concentration
I i h dli t t f li ht– Improper specimen handling: protect from light
• False Positive– Urine color interference
– Drug induced color changes: phenazyridine, indican-indoxyl sulfate
– Perform Ictotest to confirm presence of bilirubin41
Bilirubin Dipstick vs Ictotest
• Specificity is the same: both react with conjugated bilirubin
S iti it diff
42
• Sensitivity differs
Reagent strip: ~0.5 mg/dl
Ictotest: 0.05 – 0.1 mg/dl
CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 8
Ketones
• Ketones are products of incomplete fat metabolism Normally fats are completely metabolized to CO2
d tand water
• Normal = Negative
• Abnormal = Inability to utilize carbohydratesDiabetes mellitus (DKA)Inadequate intake of carbohydratesExcessive loss of carbohydrates 43
Ketones
• Fruity odor = acetone
44
Ketones
• False Negatives– Improper storage
• Volatilization
• Bacterial breakdown
• False Positives– Compounds containing free-sulfhydryl groups
– Highly pigmented urines (color interference)
45
Specific Gravity
• Specific gravity measures the concentrating and diluting abilities of the kidney; results are dependent on hydration statuson hydration status
• Normal = 1.002 to 1.035
Majority of urines are 1.010-1.025
• Abnormal = Increased SG means the urine is concentrated
= Decreased SG means the urine is dilute46
Specific Gravity
• Physiologically impossible
>1.040 (suspect interfering substance)
1.000 (suspect water)
• Sensitivity: 1.000
• Specificity: detects only ionic substances– Radiographic dye
– Mannitol
– Glucose47
Does not interfere with this method
Specific Gravity: Terms• Isosthenuria
– Fixed at 1.010
– Renal tubules lost absorption and secreting capability
• Hypersthenuria
48
– Increased specific gravity
– Concentrated urine
– Hypertonic
• Hyposthenuria– Decreased specific gravity
– Dilute urine
– Hypotonic
Sensitivity issues:
Pregnancy testing
Urinary tract infection
Protein
CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 9
Blood
• The presence of blood in the urine may indicate damage to the kidney or urinary tractg y y
• Normal = Negative
• Abnormal = Kidney stones (renal calculi)
Glomerulonephritis
Strenuous exercise
Hemolytic anemia
Transfusion reactions 49
Blood
• Blood in urine indicates pathology
• Two forms found in urine
50
– Intact RBC
– Hemolyzed RBC
Blood
• Positive with hemoglobin or myoglobin
• False Positive– Menstrual contamination
– Microbial peroxidesMicrobial peroxides
– Oxidizing agents (bleach)
• False Negative– Ascorbic acid
– High levels of protein
– High nitrite reduces strip reactivity51
Blood: Terms
• Hematuria
(intact RBC)
H l bi iAll will give a
iti bl d
52
• Hemoglobinuria
(hemolyzed RBC)
• Myoglobinuria
(muscle protein)
positive blood reaction
pH
• Kidneys help regulate the acid-base balance of the body Detects systemic acid base disordersbody. Detects systemic acid-base disorders
• Normal = 4.5 to 8.0
• Acidic = acidosis, high protein diet, starvation, dehydration, or diarrhea
• Alkaline = alkalosis, UTI, vegetarian diet, vomiting or chronic renal failure
53
pH
• Normal: ranges from 4.5 – 8.0
• First morning void: acidic
54
• Physiologically impossible: <4.5
>8.0
1. Urine not handled properly
2. Old urine
3. Treatment induced
CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 10
pH
• Invalid test results due to:– Improper handling of urine sample
Contamination of urine vessel prior to
55
– Contamination of urine vessel prior to collection
– ‘Run-over’ phenomenon (dipstick technique)
Protein
• Normal kidneys excrete little protein (<10 mg/dl) Proteinuria associated with early renal disease
• Normal = Negative (Albumin reacts)
• Transient: occurs with fever, exposure to heat or cold, emotional stress or pregnancy, exercise
• Pathological: membrane damage, disorders affecting tubular reabsorption
56
Protein
• The protein that is found in urine comes from– Bloodstream– Urinary tract
57
• Proteinuria is an indicator of early renal disease
• Proteinuria also caused by non-renal disease– Multiple myeloma
Renal Causes of Proteinuria
• Glomerular damage:– Most serious cause of proteinuria– Most common cause of proteinuria– Glomerulonephritis
N h ti S d (hi h t l l f t i )
58
– Nephrotic Syndrome (highest levels of protein)
• Tubular dysfunction:– Reabsorption capability decreased– Toxin exposure, inherited disorder– Fanconi’s syndrome: heavy metal poisoning
Protein• Sensitivity: ~ 10-25 mg/dl
• Specificity: reacts primarily with albumin
• False Positive• False Positive– Highly buffered or alkaline urine >8.0– Alkaline drugs– Improper storage and handling– Contamination of detergents
59
Protein• False Negative
– Dilute urine
– Presence of other proteins• Uromodulin (Tamm-Horsfall protein matrix in casts)
• Globulins
M l bi• Myoglobin
• Free light chains (Bence-Jones protein)
• Hemoglobin
– Exercise/transitory conditions
60
CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 11
Urobilinogen
• Urobilinogen is formed in the intestine from bili bi b b t i ( t i t d i th f )bilirubin by bacteria (most is excreted in the feces) but some is reabsorbed back into the bloodstream where small amounts are excreted in the urine
• Normal = 0.2 to 1.0 mg/dl
• Abnormal = Hemolytic disease
Liver disease
Cannot determine absence of UBG 61 62
Nitrites
• Some gram negative bacteria reduce dietary nitrates to nitrites. The bacteria that cause urinary tract infections (UTI) are often nitrite producersinfections (UTI) are often nitrite producers
• Normal = Negative
• Abnormal = UTI
Cystitis (bladder infection)
Pyelonephritis (kidney infection)
Rapid screening test for UTI 63
Nitrite• False Positive
– Substances that mask reaction color
– Foods (beets); Drugs
– Improper specimen storage/handling
F l N ti• False Negative– Ascorbic acid– Bacteria cannot reduce nitrates– Bladder time not sufficient: need 4 hours– Low nitrate levels (lacks dietary nitrates)– Antibiotic inhibition of bacteria– Further reduction of nitrites to nitrogen
64
Leukocytes
• The presence of leukocytes in the urine indicate a possible urinary tract infection Can detect intactpossible urinary tract infection. Can detect intact WBC and lysed WBC (granulocytes)
• Normal = Negative
• Abnormal = Urinary tract infection (UTI): cystitis, pyelonephritis, urethritis
65
Leukocytes• False Positive
– Substances that induce color mask
– Vaginal contamination
• False Negative• False Negative– Not waiting the two minutes
– Lymphocytes present; are not detected
– Increased glucose & protein
– Strong oxidizing agents
– Drugs
66
CLS 500 Application and Interpretation of Clinical Laboratory DataRoutine Urinalysis- Physical and Chemical Examination of Urine 12
Leukocytes
• Abnormal:– Bacterial infection:
Cystitis (bladder infection)
Pyelonephritis (kidney infection)
67
Pyelonephritis (kidney infection)
Urethritis (infection/inflammation of urethra)
– Non-bacterial infection:
Yeast
Trichomonas
Leukocytes
• Sensitivity: 5-15 WBC/hpf
• False positive
68
– Vaginal contamination
– Color masking
• False negative– Oxidizing agents (bleach)
– Lymphocytes (no granules)
Ascorbic Acid (Vitamin C)• Interferes with Reagent Strip reaction
• Causes false negative reactions for
Blood Nitrite
Bilirubin Glucose
BBNG: “Bad Boys No Good”
BGNB: “Bad Girls No Better”
University of Nebraska Medical Center
7070
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