1. INTRODUCTION TO URINALYSIS
CHAPTER 2

2. Learning Objectives
Upon completing this chapter, the reader will be able to
List three major organic and three major inorganic chemical constituents of urine.
Describe a method for determining whether a questionable fluid is urine.
Recognize normal and abnormal daily urine volumes.
Describe the characteristics of the recommended urine specimen containers.
Describe the correct methodology for labeling urine specimens.
State four possible reasons why a laboratory would reject a urine specimen.

3. Learning Objectives (cont’d)
List 10 changes that may take place in a urine specimen that remains at room temperature for more than 2 hours.
Discuss the actions of bacteria on an unpreserved urine specimen.
Briefly discuss five methods for preserving urine specimens, including their advantages and disadvantages.
Instruct a patient in the correct procedure for collecting the following specimens: random, first morning, 24-h timed, catheterized, midstream clean-catch, suprapubic aspiration, three-glass collection, and pediatric, and identify a diagnostic use for each collection technique.
Describe the type of specimen needed for optimal results when a specific urinalysis procedure is requested.

4. History The beginning of laboratory medicine
Cavemen drawings and Egyptian hieroglyphics
Color, clarity, odor, viscosity, sweetness
Fifth century BC, Hippocrates wrote uroscopy book
AD 1140 color charts
1694 albumin determination by “boiling”
Charlatans/“pisse prophets”
First medical licensure laws
17th century invention of the microscope
Evaluation of sediment
Part of a routine physical in 1827

5. Importance Readily available and easily collected specimen
Urine contains information, which can be obtained by inexpensive laboratory tests, to assess many metabolic functions
CLSI Urinalysis definition: “the testing of urine with procedures commonly performed in an expeditious, reliable, safe, and cost-effective manner”
Reasons to perform
Aid disease diagnosis, screen for asymptomatic diseases, monitor disease progress and therapy effectiveness

6. Urine Formation Ultrafiltrate of plasma
Kidneys converts approximately 170,000 mL of filtered plasma
Average daily urine output of 1200 mL

7. Urine Composition Normal 95% water, 5% solutes
Solute variations: diet, activity, metabolism, endocrine, body position
Major organic solute is urea (protein, amino acid breakdown); makes up approximately one half of the dissolved solids
Inorganic chloride, sodium, and potassium
Urea and creatinine identify a fluid as urine
May also contain cells, casts, crystals, mucus, and bacteria
Increases indicative of disease

8. Urine Volume Determined by body’s state of hydration
Influenced by fluid intake, nonrenal fluid loss, antidiuretic hormone (ADH) variations, excretion of large amounts of dissolved solids (e.g., glucose)
Usual daily volume = 1200 to 1500 mL
Normal range = 600 to 2000 mL

9. Definitions Oliguria: a decrease in urine output
<1 mL/kg/h in infants <0.5 mL/kg/h in children, <400 mL/day in adults
Causes: vomiting, diarrhea, perspiration, severe burns
Anuria: cessation of urine flow
Severe kidney damage, decreased renal blood flow
Nocturia: increased urine excretion at night
Normally two to three times more excretion in the day
Polyuria: >2.5 L/day in adults and >2.5 to 3 mL/kg/day in children

10. Polyuria in Diabetes Mellitus versus Diabetes Insipidus
Increased volume caused by need to excrete the excess glucose not reabsorbed from the ultrafiltrate
Patients exhibit polydipsia (Increased water intake)
Urine appears dilute with a high specific gravity
Decreased production or function of antidiuretic hormone (ADH) causing decreased reabsorption of water from ultrafiltrate
Urine is dilute with low specific gravity
Patients also exhibit polydipsia

11. Specimen Collection Wear gloves when working with urine
Clean, dry, leak-proof containers
Disposable, wide-mouthed, and flat-bottom containers with screw caps are recommended
Clear containers/at least 50 mL capacity
Sterile transfer devices and containers are available
Facilitates automated analysis
12 mL minimum for analysis
Adhesive bags for pediatrics
Large plastic containers for 24-hour specimens

12. Specimen Labeling Information on label
Patient’s name, ID number, date, time
Additional information: age, location, health-care provider’s name
Place label on container, not lid
Requisition form (manual or computerized)
Must accompany specimen
Information must match label
Time of receipt is stamped on requisition
Other information: type of specimen, interfering medications

13. Specimen Rejection Specimens in unlabeled containers
Nonmatching labels and requisition forms
Specimens contaminated with feces or toilet paper
Containers with contaminated exteriors
Specimens of insufficient quantity
Specimens that have been improperly transported
Labs must have written policies for rejection of specimens

14. Specimen Integrity
Changes in urine composition take place not only in vivo but also in vitro
Test within 2 hours of collection
Refrigerate or chemically preserve if testing is delayed
Most problems are caused by bacterial multiplication
Increased: color, turbidity, pH, nitrite, bacteria, odor
Decreased: glucose, ketones, bilirubin, urobilinogen, RBCs, WBCs, casts

15. Changes in Unpreserved Urine
Analyte
Change
Cause
Color
Modified/darkened
Oxidation or reduction of metabolites
Clarity
Decreased
Bacterial growth and precipitation of amorphous material
Odor
Increased
Bacterial multiplication causing breakdown of urea to ammonia pH
Breakdown of urea to ammonia by urease-producing bacteria/loss of CO2
Glucose
Glycolysis and bacterial use

16. Changes in Unpreserved Urine (cont’d)
Analyte
Change
Cause
Ketones
Decreased
Volatilization and bacterial metabolism
Bilirubin
Exposure to light/photooxidation to biliverdin
Urobilinogen
Oxidation to urobilin
Nitrite
Increased
Multiplication of nitrate-reducing bacteria
RBCs, WBCs, and casts
Disintegration in dilute alkaline urine
Bacteria
Multiplication
Trichomonas
Loss of motility, death

17. Specimen Preservation
Routine is refrigeration at 2°C to 8°C
Decreases bacterial growth and metabolism
Must return to room temperature for chemical testing
Chemical preservative
Ideal is bactericidal: inhibits urease and preserves formed elements
Should not interfere with chemical tests
Commercial transport tubes are available, but they must be compatible with tests

18. Preservatives Preservatives Advantages Disadvantages
Additional Information
Refrigeration
Does not interfere with chemical tests
Precipitates amorphous phosphates and urates
Prevents bacterial growth for 24 h2
Boric acid
Prevents bacterial growth and metabolism
Interferes with drug and hormone analyses
Keeps pH at about 6.0
Can be used for urine culture transport
Formalin (formaldehyde)
Excellent sediment preservative
Acts as a reducing agent, interfering with chemical tests for glucose, blood, leukocyte esterase, and copper reduction
Rinse specimen container with formalin to preserve cells and casts
Sodium fluoride
Is a good preservative for drug analyses
Inhibits reagent strip tests for glucose, blood, and leukocytes

19. Preservatives (cont’d)
Advantages
Disadvantages
Additional Information
Commercial preservative tablets
Convenient when refrigeration not possible
Have controlled concentration to minimize interference
Check tablet composition to determine possible effects on desired tests
Urine Collection Kits4 (Becton Dickinson, Rutherford, NJ)
Contains collection cup, transfer straw, C&S preservative tube or UA tube
Light gray and gray C&S tube
Sample stable at room temperature (RT) for 48 h; prevents bacterial growth and metabolism
Do not use if urine is below minimum fill line
Preservative is boric acid, sodium borate, and sodium formate
Keeps pH at about 6.0

20. Types of Specimen
The composition of urine depends on the patient’s metabolic state and the timing and procedure used for collection
Time, length, and method of collection and the patient’s dietary and medicinal intake
Patients must be instructed when special collection techniques are required

21. Random Specimen Most common type received
Routine screening for obvious abnormalities
May be collected at any time
Collection time must be recorded
Dietary intake and physical activity may alter results
Patients may have to collect an additional specimen under controlled conditions

22. First Morning Specimen
Ideal screening specimen
Patient is in a basal state
Use for orthostatic protein confirmation and urine pregnancy tests
More concentrated than a random specimen
Patient collects immediately on arising, delivers to lab within 2 hours
Refrigeration is an alternative

23. Fasting Specimen
Actually is second specimen voided, collected after the first morning specimen
Does not contain metabolites from evening meal
Recommended for glucose monitoring

24. 24-Hour (Timed) Specimen
Carefully timed specimen will produce accurate quantitative results
Good for diurnal variation solutes
Catecholamines, electrolytes
The patient must remain adequately hydrated during short collection period
Patient must be instructed on the procedure for collecting a timed specimen
Concentration of a substance in a particular period must be calculated from the urine volume produced during that time

25. 24-Hour (Timed) Specimen (cont’d)
24-hour specimen must be thoroughly mixed and the volume accurately measured and recorded
Multiple containers of the same collection must be combined and mixed thoroughly
Additives should not interfere with the tests to be performed

26. 24-Hour (Timed) Specimen (cont’d)
Required for quantitative results
24-hour specimens are needed for measuring substances with diurnal variation (results differ in a.m. and p.m.) and substances that vary with meals, activity, and body metabolism
Shorter timed specimens can be used for substances with consistent levels
Accurate timing is critical for accurate results

27. 2-Hour Postprandial Specimen
Patient voids before eating routine meal
Eats meal
Collects next specimen 2 hours after finishing meal
Monitors insulin therapy
Results can be compared with fasting urine specimen and blood test results

28. Glucose Tolerance Specimen
Institutional option for collection with blood glucose tolerance test, not frequently done
Specimens are collected at the same intervals as the blood samples
Used to correlate renal threshold with patient’s ability to metabolize glucose

29. Catheterized Specimens
Sterile specimen collected from bladder with a hollow tube (catheter)
Most common test is bacterial culture

30. Midstream Clean-Catch Specimen
Alternative to catheterized specimen
Less traumatic method
Less contaminated than routine collection
Provide patient with mild cleansing material and container and instructions
Do not touch or contaminate inside of container

31. Suprapubic Aspiration
Completely free of contamination for culture and cytology
External introduction of needle for aspiration from the bladder
Possible pediatric specimen

32. Prostatitis Specimen Collection similar to midstream clean-catch
Three-glass collection
Container 1: first urine passed
Container 2: midstream urine
Massage prostate to obtain prostatic fluid
Container 3: remaining urine and fluid
Quantitative cultures on all three specimens, examine 1 and 3 microscopically for WBCs

33. Prostatitis Specimen (cont’d)
Prostatic infection = higher WBC/hpf count in specimen 3 than specimen 1; bacterial count in specimen 3 is 10 times higher than in specimen 1
Specimen 2 is a control for bladder or kidney infection
Positive culture in specimen 2 invalidates positive culture in specimen 3 (cannot differentiate urinary tract infection from prostate infection)

34. Prostatitis Specimen (cont’d)
Pre- and postmassage test
Specimen 1: midstream clean-catch specimen
Specimen 2: postmassage specimen
Prostatitis is indicated by a quantitative culture result in the second glass that is 10 times higher than specimen 1

35. Pediatric Specimens
Soft, clear, plastic bags, with hypoallergenic tape applied to genital area
Monitor bag frequently
Clean-catch method with sterile bag can be used
Cleaning for microbiology specimens
Bags with tubes to a larger container are available for timed specimens

36. Drug Specimen Collection
Proper collection, labeling, and handling must be documented
Chain of custody: documentation from the time of specimen collection until the time of receipt of laboratory results
Free of substitution, adulteration, or dilution
Standardized form always accompanies specimen
Specimen must withstand legal scrutiny

37. Drug Specimen Collection (cont’d)
Points to consider
Photo ID of urine donor or ID by employer
No unauthorized access to specimen
Witnessed versus unwitnessed collection
Determined by test orderer
Both specimens must be handed immediately to collector

38. Drug Specimen Collection (cont’d)
Adulteration tests
Temperature taken within 4 minutes must be 32.5°C to 37.7°C
Report temperatures outside of range immediately
Collect another specimen ASAP
Inspect urine color for anything unusual
Follow laboratory instructions for labeling, packaging, and transport