MLSP MAcroscopic and chemical examination of urine

• Gloves


  • Should be worn at all times when in contact with the specimen
• Urine collection responsibilities of Medtech

  1. Instruct the patient on how to properly collect his or her urine

  2. Receive the specimen (wear PPE)

  
• Urine collection containers


  • Clean, dry, leak-proof, screw top lids, wide mouth, clear
  • Disposable containers are recommended
• Specimen integrity


  • Specimens should be delivered to the laboratory promptly and tested withing 2 hours
  • A specimen that cannot be delivered and tested within 2 hours should be refrigerated or have an appropriate chemical preservative added
• Physical examination of urine

  • Color
  • Clarity
  • Volume
  • Odor

  
• Normal urine color


  Pale yellow, yellow, dark yellow, and amber
• Abnormal urine colors


  • Dark Yellow or Amber - presence of the abnormal pigment bilirubin
  • Yellow-orange - administration of phenazopyridine (pyridium) or azogantrisin compounds to persons with urinary tract infections
  • Red - presence of blood
  • Brown Urine containing Blood - glomerular bleeding
  • Brown or black - melanin or homogentisic acid, levodopa, methyldopa, phenol derivatives, and metronidazole (Flagyl)
  • Blue/Green - bacterial infections, including urinary tract infection by Pseudomonas species and intestinal tract infections resulting in increased urinary indican
• Color and clarity procedure

  1. Use a well-mixed specimen

  2. View through a clear container

  3. View against white background

  4. Maintain adequate room lighting

  5. Evaluate a consistent volume of specimen

  6. Determine color and clarity
• Odor of urine


  Freshly voided urine: faint aromatic odor
• Reagent strips


  • Sometimes called "dip strips"
  • Consist of chemical-impregnated absorbent pads attached to a plastic strip
  • A color-producing chemical reaction takes place when the absorbent pad comes in contact with urine
  • 10 parameter reagent strip (10 little square: you can do 10 chemical tests in 1 going)
  • The reactions are interpreted by comparing the color produced on the pad with a chart supplied by the manufacturer
• Care of reagent strips

  • Store with desiccant in an opaque, tightly closed container
  • Store below 30C [room temperature]; do not freeze
  • Do not expose to volatile fumes
  • Do not use past the expiration date
  • Do not use if chemical pads become discolored
  • Remove strips immediately prior to use
• Reagent strip procedure


  1. Mix specimen well

  2. Let refrigerated specimens warm to room temperature before testing

  3. Dip the strip completely, but briefly, into specimen

  4. Remove excess urine by withdrawing the strip against the rim of the container and by blotting the edge of the strip

  5. Compare reaction colors with the manufacturer's chart under a good light source at the specified time

  6. Perform backup tests when indicated

  7. Be alert for the presence of interfering substances

  8. Understand the principles and significance of the test, read package inserts

  9. Relate chemical findings to each other and to the physical and microscopic urinalysis results
• Quality control of reagent strips

  • Test open bottles of reagent strips with known positive and negative controls every 24 hours
  • Resolve control results that are out of range by further testing
  • Test reagents used in backup tests with positive and negative controls
  • Perform positive and negative controls on new reagents and newly opened bottles of reagent strips
  • Record all control results and reagent lot numbers
• pH


  • Aid in determining the existence of systemic acid-base disorders of metabolic or respiratory origin and in the management of urinary conditions that require the urine to be maintained a specific pH
  • First morning specimen [most concentrated]– slightly acidic pH of 5.0-6.0
  • Normal random samples [wide range of value]– 4.5 to 8.0
  • Reagents – methyl red, bromthymol blue

  
• Clinical significance of urine pH


  • Respiratory or metabolic acidosis/ketosis
  • Respiratory or metabolic alkalosis
  • Defects in renal tubular secretion and reabsorption of acids and bases – renal tubular acidosis
  • Renal calculi formation
  • Treatment of urinary tract infections
  • Precipitation/identification of crystals
  • Determination of unsatisfactory specimens

  
• Protein

  • Most indicative of renal disease
  • Normal urine - <10 mg/dL or 100 mg per 24 hrs
  • Clinical proteinuria - 30 mg/dL (300 mg/L)
  • Increase in protein contents in the urine that indicates disease or disorder
• Urine pH


  Indicator of:
• Protein in urine


  • Most indicative of renal disease
  • Protein should not be found in large quantities in the urine
  • Normal urine - <10 mg/dL or 100 mg per 24 hrs
  • Clinical proteinuria - 30 mg/dL (300 mg/L)
• Sources of error/interference for protein in urine

  • False-positive: Highly buffered alkaline urine, Pigmented specimens, Phenazopyridine, Quaternary ammonium compounds (detergents), Antiseptics, Chlorhexidine, Loss of buffer from prolonged exposure of the reagent strip to the specimen, High specific gravity
  • False Negative: Proteins other than albumin, Microalbuminuria
• Glucose in urine


  • Most frequent chemical analysis performed on urine
  • Detection and monitoring of diabetes mellitus

  
• Sources of error/interference for glucose in urine

  • False-positive: Contamination by oxidizing agents and detergents
  • False-negative: High levels of ascorbic acid, High levels of ketones, High specific gravity, Low temperatures, Improperly preserved specimens

  
• Ketones


  Represent three intermediate products of fat metabolisms: Acetone, Acetoacetic acid, Beta-hydroxybutyric acid
• Ketonuria


  • Shows a deficiency in insulin, indicating the need to regulate dosage
  • It is often an early indicator of insufficient insulin dosage in type 1 diabetes and in patients with diabetes who experience medical problems in addition to diabetes
• Clinical significance of ketones

  • Diabetes acidosis
  • Insulin dosage monitoring
  • Starvation
  • Malabsorption/pancreatic disorders
  • Strenuous exercise
  • Vomiting
  • Inborn errors of amino acid metabolism [congenital disorder]

  
• Blood in urine


  May be present in the form of intact red blood cells (hematuria) or as the product of blood cell destruction, hemoglobin (hemoglobinuria)
• Sources of error/interference for blood in urine

  • False-positive: Strong oxidizing agents, Bacterial peroxidases, Menstrual contamination
  • False-negative: High specific gravity/crenated cells, Formalin, Captopril, High concentrations of nitrite, Ascorbic acid 25 mg/dL, Unmixed specimens
• Bilirubin


  • An early indication of liver disease
  • Often detected long before the development of jaundice
• Clinical significance of bilirubin

  • Hepatitis
  • Cirrhosis
  • Other liver disorders
  • Biliary obstruction (gallstones, carcinoma)
• Urobilinogen


  • Circulates in the blood en route to the liver, it passes through the kidney and is filtered by the glomerulus
  • Normal value: <1 mg/dl or Ehrlich
  • Increased urine urobilinogen (greater than 1 mg/dl) is seen in liver disease and hemolytic disorders
• Clinical significance of urobilinogen

  • Early detection of liver disease
  • Liver disorders, hepatitis, cirrhosis, carcinoma
  • Hemolytic disorders
• Nitrite


  • Provides a rapid screening test for the presence of urinary tract infection (UTI)
  • Valuable for detecting initial bladder infection (cystitis)
  • Chemical basis: ability of certain bacteria to reduce nitrate, a normal constituent of urine, to nitrite, which does not normally appear in the urine

  
• Sources of error/interference for nitrite

  • False-negative: Nonreductase-containing bacteria, Insufficient contact time between bacteria and urinary nitrate, Lack of urinary nitrate, Large quantities of bacteria converting nitrite to nitrogen, Presence of antibiotics, High concentrations of ascorbic acid, High specific gravity
  • False-positive: Improperly preserved specimens, Highly pigmented urine [old – produce bacteria]
• Clinical significance of nitrite


  • Cystitis
  • Pyelonephritis
  • Evaluation of antibiotic therapy
  • Monitoring of patients at high risk for urinary tract infection
  • Screening of urine culture specimens

  
• Leukocyte esterase


  • More standardized means for the detection of leukocytes
  • Enzyme that WBC release during phagocytosis
  • If this is positive, but negative in nitrite (UTI not caused by bacteria)
  • Infections caused by trichomonas, chlamydia, yeast, and inflammation of renal tissues (i.e. interstitial nephritis) produce leukocyturia without bacteriuria
• Clinical significance of leukocyte esterase

  • Bacterial and nonbacterial urinary tract infection
  • Inflammation of the urinary tract
  • Screening of urine culture specimens
• Specific gravity


  • Measures only ionic solutes
  • Eliminating the interference by the large organic molecules, such as urea and glucose, and by radiographic contrast media and plasma expanders that are included in physical measurements of specific gravity
• Clinical significance of specific gravity

  • Monitoring patient hydration and dehydration
  • Loss of renal tubular concentrating ability
  • Diabetes insipidus
  • Determination of unsatisfactory specimens due to low concentration
• There are timers for different urine test parameters:
• Urine sediment preparation and examination: