Urinalysis and Body Fluids, 5th Edition

INTRODUCTION TO URINALYSIS

History of Urinalysis

• Cavemen and Egyptians examined urine for:
  • Color
  • Clarity
  • Odor
  • Viscosity
  • Sweetness
• Hippocrates authored a significant book on uroscopy.
• Early chemical tests for:
  • Glucose
  • Protein
• Existence of charlatans, referred to as "pisse prophets."
• Development of the first medical licensure laws.
• Urinalysis established as a routine physical exam in 1827.

Importance of Urinalysis

• Urinalysis serves as an easily obtained specimen to assess many metabolic functions through inexpensive tests.
• Definition of Urinalysis:
  • "The testing of urine with procedures commonly performed in an expeditious, reliable, safe, and cost-effective manner."
• Reasons to perform urinalysis include:
  • Aid in disease diagnosis
  • Screen for asymptomatic diseases
  • Monitor disease progress and therapy effectiveness.

Urine Composition

Normal Composition

• Urine typically consists of:
  • 95% water
  • 5% solutes
• Variations in solute content can occur due to:
  • Diet
  • Activity level
  • Metabolism
  • Endocrine factors
  • Body position changes
• Major organic solutes in urine:
  • Urea (derived from protein and amino acid breakdown)
  • Creatinine
  • Uric acid
• Identification:
  • Urea and creatinine help determine if a fluid is urine.

Inorganic Components

• Inorganic constituents of urine include:
  • Chloride
  • Sodium
  • Potassium
• Establishing normal values can be complex due to dietary influences.
• The presence of formed elements not part of ultrafiltrate may indicate illness.

Urine Volume

Determining Factors

• Urine volume is dictated by:
  • Body hydration state
  • Fluid intake
  • Nonrenal fluid loss
  • Variations in antidiuretic hormone (ADH)
  • Excretion of large amounts of dissolved solids (e.g., glucose)
• The usual daily volume of urine is between:
  • 1200-1500 mL
• Normal range spans:
  • 600-2000 mL

Definitions of Urine Volume Conditions

• Oliguria:
  • Defined as urine output <400 mL/day in adults.
  • Possible causes include:
  • Vomiting
  • Diarrhea
  • Perspiration
  • Severe burns
• Anuria:
  • Cessation of urine production.
  • May result from severe kidney damage or decreased renal blood flow.
• Nocturia:
  • Increased urine excretion at night, typically 2-3 times the daytime excretion.
• Polyuria:
  • Excessive urination defined as >2.5 L/day.

Polyuria in Diabetes Types

• Diabetes Mellitus:
  • Increased urine volume arises from the need to excrete excess glucose not reabsorbed from ultrafiltrate.
  • Patients usually exhibit polydipsia; urine appears dilute, with high specific gravity.
• Diabetes Insipidus:
  • Involves decreased production or function of ADH, reducing water reabsorption from ultrafiltrate.
  • Resulting urine is dilute, showing low specific gravity; patients also exhibit polydipsia.

Specimen Collection

Recommended Containers

• Use disposable, wide-mouthed, flat-bottom containers with screw caps.
• Ensure containers are clear and have at least a 50 mL capacity.
• Use adhesive bags for pediatric specimens and large plastic containers for 24-hour specimens.
• Gloves should be worn when handling urine specimens.

Specimen Labeling Requirements

• Labels must include:
  • Patient's name
  • Patient's ID number
  • Date and time of collection
  • Additional details:
  • Age
  • Location
  • Physician’s name
• Important: Place label on the container, not the lid.
• A requisition form must accompany the specimen.
  • Ensure that information matches the label.
  • The time of receipt is stamped on the requisition, along with details about the specimen type and any interfering medications.

Specimen Rejection Criteria

Specimens may be rejected for the following reasons:

• Unlabeled containers
• Non-matching labels and requisitions
• Contaminated specimens (e.g., feces, paper)
• Contaminated containers
• Insufficient quantity
• Delayed or improper transport, such as not being kept on ice or refrigerated
• Laboratories have written policies regarding specimen rejection.

Specimen Integrity and Timeframe for Testing

• Recommended to test urine within 2 hours of collection.
• If testing is delayed, specimens should be refrigerated to prevent degradation.
• Common issues during delays include:
  • Increased color, turbidity, pH, nitrite, bacteria, and odor
  • Decreased glucose, ketones, bilirubin, urobilinogen, RBCs, WBCs, and casts.

Changes in Unpreserved Urine

Table 3-2: Analyte Changes Over Time

Specimen Preservation Techniques

• Ideal preservation methods should be bactericidal, inhibit urease activity, preserve formed elements, and not interfere with chemical testing.
• Routine preservation involves refrigeration, especially critical for culture specimens.
  • Refrigeration can cause precipitation of amorphous crystals.
  • Specimen containers must return to room temperature before chemical testing.
  • Commercial transport tubes must be compatible with tests used.

Types of Specimens

• The urine's composition varies based on the patient’s metabolic state and collection timing/procedures.
• Special collection techniques may be required, with adequate instructions for patients.

Random Specimen

• The most commonly received type, used for routine screening to detect obvious abnormalities.
• Can be collected at any time but may be affected by dietary intake and activity.
• Patients might need to collect follow-up specimens.

First Morning Specimen

• Considered the ideal screening specimen due to higher concentration than random specimens.
• Obtained immediately upon waking, crucial for:
  • Orthostatic protein confirmation
  • Urine pregnancy tests
• Must be delivered to the lab within 2 hours of collection.

Fasting Specimen

• This is actually the second specimen voided, collected after the first morning specimen.
• It does not include metabolites from the evening meal.
• Recommended for glucose monitoring/screening purposes.

2-Hour Postprandial Specimen

• Procedure involves:
  1. Patient voids before eating a routine meal.
  2. The patient eats the meal.
  3. Collect the next specimen 2 hours post-meal.
• Used for monitoring insulin therapy and comparing results with fasting urine specimens and blood tests results.

Glucose Tolerance Specimen

• This specimen collection is institutional and accompanies blood glucose tolerance tests, though infrequently performed.
• Samples are collected at the same intervals as blood samples to correlate renal threshold with the patient’s glucose metabolism ability.

24-Hour (Timed) Specimen

• Essential for obtaining quantitative results.
• Necessary for measuring substances with diurnal variation and those that vary with meals, activity, and metabolism.
• Shorter timed specimens may suffice for substances with consistent levels.
• Accurate timing is crucial to ensure results hold validity.

Timing Schedule Example

• 7 a.m: Patient voids and discards urine.
• Patient begins collecting urine from 7 a.m. onwards for 24 hours.
• 7 a.m. next day: Patient voids again, adding this urine to the collection container.
• Key principle: Collection must begin and end with an empty bladder.
• Calculation for units measured over 24 hours includes mL of urine collected.

Handling of Timed Specimens

• Thoroughly mix specimens and measure accurately.
• Store a sufficient aliquot for testing, allowing for retesting if needed.
• Keep specimens on ice or refrigerated during the collection process.
• Employ appropriate and non-toxic preservatives.
• Review the instructions thoroughly with the patient to ensure compliance.

Catheterized Specimens

• Sterile urine samples obtained through catheterization from the bladder.
  • Most commonly utilized for culture and sensitivity tests.
  • Culturing should be prioritized before routine analysis.

Midstream Clean-Catch Specimen

• This method serves as an alternative to catheterized specimens, providing lower contamination levels than typical collection.
• Patients should be given:
  • Mild cleansing materials
  • Containers with clear instructions:
  1. Wash hands.
  2. Clean genitalia with the supplied cleanser.
  3. Void into the toilet, then into the container, finishing back into the toilet.
  4. It is crucial not to touch or contaminate the interior of the container.

Suprapubic Aspiration

• Method yielding specimens entirely free of contamination for both culture and cytological analysis.
• Involves external needle aspiration from the bladder.
• It can also be used as a method for obtaining pediatric urine specimens.

Prostatitis Specimen Collection

• The collection follows a midstream clean-catch method, known as the 3-glass collection:
  1. Container 1: First urine passed.
  2. Container 2: Midstream urine.
  • The prostate is massaged to obtain prostatic fluid.
  1. Container 3: Remaining urine and fluid.
• Cultures are performed on all three specimens, while specimens 1 and 3 are examined microscopically for white blood cells (WBCs).

Prostatitis Specimen Results Interpretation

• A diagnosis of prostatic infection occurs when:
  • Specimen 3 shows a higher WBC/hpf count than Specimen 1,
  • Bacterial count in Specimen 3 is 10 times higher than in Specimen 1.
• Specimen 2 serves as a control for bladder or kidney infections.
• A positive culture result in Specimen 2 negates the validity of any positive results found in Specimen 3, as it cannot differentiate between urinary tract and prostate infections.

Variations in Prostate Specimens

• Stamey-Mears 4-glass collection:
  1. Initial voided (VB1).
  2. Midstream (VB2).
  3. Massaged prostate excretions (EPS).
  4. Post-massage urine (VB3).
• Cultures are performed on each specimen.
• Interpretations:
  • Positive results for VB1 and VB2 indicate urinary infection.
  • EPS must show WBC >10-20/hpf to be considered abnormal.
  • Negative cultures on VB1 and VB2 with positive results on EPS and VB3 suggest prostatitis.

Pre- and Post-Massage Testing

• Involves:
  1. Specimen 1: midstream clean-catch specimen.
  2. Specimen 2: post-massage specimen.
• Prostatitis is indicated when the quantitative culture in the second specimen shows a count that is 10 times higher than in specimen 1.

Pediatric Specimens

• Use soft, clear plastic bags with hypoallergenic tape applied to the genital area.
• Frequent monitoring of the bag is required.
• A clean-catch method can be performed with a sterile bag.
• Bags with tubes leading to larger containers can be used for timed collections.

Drug Specimen Collection

• Proper specimen collection, labeling, and handling are crucial to ensure documentation throughout the entire chain of custody:
  • The chain of custody is vital for legal scrutiny, tracking from specimen collection to laboratory result receipt.
• Always utilize standardized forms to accompany specimens.

Points to Consider in Drug Specimen Collection

• Ensure the urine donor presents a photo ID or identification from their employer.
• Ensure no unauthorized access occurs to the specimen.
• Address issues of potential adulteration, substitution, or dilution of the specimen (tampering).
• The collection can be either witnessed or unwitnessed as determined by the ordering entity, and both specimens must be immediately handed to the collector.

Adulteration Tests

• The temperature of the sample must be taken within 4 minutes post-collection and must fall between 32.5-37.7°C.
• Report any temperature readings outside the specified range immediately to initiate further action, including collecting another specimen as soon as feasible.
• Inspect urine color for unusual characteristics before proceeding with testing.
• Follow laboratory protocols for labeling, packaging, and transporting specimens.