Introduction to Urinalysis PDF

Introduction to Urinalysis URINALYSIS & BODY FLUIDS B Y S T R A S I N G E R , S. & D I LO R E N Z O, M. (7 T H ED) – CHAPTER 3  History Urine analysis was the beginning of laboratory medicine. Cave drawings and Egyptian hieroglyphics show references to the...

Introduction to Urinalysis URINALYSIS & BODY FLUIDS B Y S T R A S I N G E R , S. & D I LO R E N Z O, M. (7 T H ED) – CHAPTER 3  History Urine analysis was the beginning of laboratory medicine. Cave drawings and Egyptian hieroglyphics show references to the study of urine. Diagnostic information could be obtained from the color, turbidity, odor, volume, viscosity and sweetness of the urine sample. Because of advances in science and the invention of the microscope, modern urinalysis includes chemical analysis and  Why Do We Perform Urinalysis? According to the Clinical and Laboratory Standards Institute (CLSI) reasons to perform urinalysis include: To aid in diagnosis of disease To screen asymptomatic populations for undetected disorders To monitor the progress of disease To monitor the effectiveness of therapy Urine is readily available and easily collected!   Why Do We Perform To detect overall Urinalysis? body disturbances Ex. Metabolic problems (diabetes mellitus) To detect kidney/urinary tract problems May see an increase/decrease in fluid May see structural elements (eg. cells, casts, protein) Liver disturbances Bilirubin/urobilinogen Genetic Defects (eg. Phenylketonuria PKU) It is the most practical starting point Cheap Non-invasive  Urine Composition Approximately: 95% water 5% solutes The concentration of solutes will vary depending on dietary intake, physical activity, body metabolism, and endocrine function.  Major Organic Components in Normal Urine Urea accounts for almost 50% of dissolved solutes. Metabolic waste product produced in the liver from the breakdown of protein and amino acids. Other organic substances include creatinine and uric acid. Creatinine - product of creatine metabolism by muscles Uric acid - product of nucleic acid breakdown in food and cells  Major Inorganic Components in Normal Urine Chloride - Primary inorganic component. - Found in combination with sodium and other inorganic substances. Sodium - Primarily from salt Potassium - Combined with chloride and other salts Small or trace amounts of: Phosphate - combines with Na+ to buffer the blood Ammonium - Regulates blood and tissue fluid acidity Calcium - Combines with chloride, sulfate, and phosphate  Urine Volume The normal volume of urine voided each day by an adult can range from 600-2000 mL, with a typical volume of 1200-1500 mL. Factors that influence urine volume include: Fluid intake Fluid loss from nonrenal sources Variations in the secretion of antidiuretic hormone (ADH)  Decreased Urine Volume Oliguria A decrease in urine output Decreased urine excretion (2.5 L/day) Associated with: Diabetes mellitus and diabetes insipidus Can be artificially induced by: Diuretics, caffeine or alcohol - all suppress secretion of ADH  Diabetes Mellitus vs. Diabetes Urine analysis can aidInsipidus in the differential diagnosis between these types of diabetes.  Specimen Collection - Containers Must be collected in clean, dry, leak-proof containers. Containers should be disposable. Containers must have screw-top lids to prevent leaks. Containers for routine urinalysis: Wide mouth and wide bottom to prevent tipping 50 mL capacity Clear material to determine color and clarity Sterile containers for microbiology testing  Specimen Collection - Labels & Requistions Specimens must be labelled with: Patient’s name Healthcare number Date and time of collection Labels must be attached to the container, not the lid! A requisition must accompany the urine specimen. The information on the requisition must match the information on the specimen label.  Specimen Rejection Criteria Specimens in unlabeled containers Patient information (name, healthcare #) on specimen does not match patient information on requisition Specimens contaminated with feces or toilet paper Containers with contaminated exteriors / leaking Specimens of insufficient quantity Specimens that have been improperly transported or > 24 hours old  Specimen Rejection Criteria Specimens that were not properly preserved Specimens for urine culture in nonsterile container Inappropriate collection for type of testing needed Labs must have written policies for rejection of specimens  Specimen Handling The analysis is only as good as the sample Collection, handling, processing and reporting must adhere to laboratory standards Specimens for urinalysis should be tested within 2 hours If testing must be delayed refrigerate and/or place sample in preservative Changes in urine composition will take place if urine is not properly preserved. Most changes are due to the presence and growth of bacteria.  Specimen Integrity Analyze within two hours; delays can cause Increase in: Decrease in: Bacteria Bilirubin pH Urobilinogen Glucose RBCs Casts If testing can not occur within two hours, preserve specimen Refrigeration Chemical preservatives BD Urinalysis Preservation Tube BD C&S Preservative Tube  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 Increased Breakdown of urea to ammonia by urease-producing bacteria/loss of CO2 Glucose Decreased Glycolysis and bacterial use  Changes in Unpreserved Urine Analyte Change Cause Ketones Decreased Volatilization and bacterial metabolism Bilirubin Decreased Exposure to light/photooxidation to biliverdin Urobilinogen Decreased Oxidation to urobilin Nitrite Increased Multiplication of nitrate-reducing bacteria RBCs, WBCs, Decreased Disintegration in dilute alkaline urine and casts Bacteria Increased Multiplication Trichomonas Decreased Loss of motility, death  Urine Preservatives Most common method is refrigeration between 2-8oC. Specimens should be transported and kept under refrigerated conditions until analyzed or cultured. (up to 24 hours) Specimens should be allowed to return to room temperature prior to chemical reagent strip testing. Enzyme reactions on the strip perform best at room temp. If specimens cannot be refrigerated during transport, chemical preservatives may be added.  “Ideal” Urine Preservatives Bactericidal Inhibit urease Preserve formed elements in urine sediment Not interfere with chemical tests Because “ideal” preservative doesn’t exist, choose preservative based on the needs of the test ordered.  Urine Preservatives From Table 3-3 Preservative Advantages Disadvantages Other info Refrigeration Does not interfere Precipitates Prevents bacterial with chemical tests amorphous growth for 24 hours phosphates and urates Boric Acid Prevents bacterial Interferes with Keeps pH at about growth and analysis of drugs 6.0. Can be used for metabolism and hormones culture transport. Commercial Convenient when preservative refrigeration not tablets possible Gray C&S Tube Stable at RT for 48 Do not use if urine Preservative is boric hrs is below minimum acid, sodium Prevents bacterial fill line borate, and sodium growth and formate  Types of Specimens Random First Morning 24-Hour (or Timed) Catheterized Midstream Clean-Catch Suprapubic Aspiration Pediatric Generally a more concentrated specimen is preferred (rather than a dilute urine).  Random Specimen Most common type of urine specimen received in the lab AKA Spot specimen Convenient - can be collected at any time Good for most routine testing (physical, chemical, microscopic)  First Morning Specimen A more concentrated specimen than random urines Good detection of chemicals and formed elements that may not appear in a random dilute urine. Incubated in bladder overnight Pros: Best specimen for nitrite, protein and microscopic analysis Bacteria has time to reduce nitrate to nitrite Best specimen for urine pregnancy testing. The more concentrated sample prevents false-negatives Good for evaluating orthostatic proteinuria. Cons: Casts may be deteriorated If there is bacteria in the specimen, it can impact glucose analysis (↓glucose)  24-Hour or Timed Specimen All voidings collected for a given period of time To start: Empty bladder (don’t include it), start timing, collect all voidings. At end of time, void and include it. Produce quantitative results. Usually 2, 12 or 24 hours 2 hour good for urobilinogen (maximum excretion between 1-3 or 2- 4 pm) 24 hour good for quantitating protein, creatinine and electrolytes Patient Instructions How would not emptying the bladder at the start and discarding that urine affect results? Falsely increase results  24-Hour or Timed Specimen All specimens should be refrigerated during the collection period. Some specimens may require addition of chemical 24-hour specimens must be mixed preservative. well upon arrival to the lab. The volume is measured and recorded. If the patient has more than one container, the contents of all containers must be mixed. After mixing, a small sample is  Common Errors with Timed Urines Loss of urine specimen (ex. patient doesn’t submit all voidings, leaks) Inclusion of two first morning specimens Inaccurate measurement of total volume Inadequate/Incorrect preservative used Transcription error  Catheterized Specimen Collected under sterile conditions. A hollow tube is passed through the urethra into the bladder. Bacterial cultures are the most common test requested on catheterized specimens.  Midstream Clean-Catch Specimen Patient should be provided with cleansing wipes and instructions. Patient urinates first part into toilet, then collects urine into the container and voids the remainder into the toilet. Less contaminated with epithelial cells and bacteria  Clean-Catch Urine Collection Procedure For 1.Wash hands thoroughly Women 2. Remove lid of container without touching inside of cover or container 3. Stand in a squatting position over toilet. 4. Separate folds of skin around urinary opening. 5. Cleanse by wiping from front to back. Discard used wipes in trash. 6. While keeping skin folds separated, void into toilet for a few seconds. 7. Touching only outside of container, bring container into urine stream until sufficient amount is collected (30-100 mL) 8. Void any additional urine into toilet. 9. Screw on lid, only touching outer surfaces. 10. Clean any urine off of outside of container using antiseptic  Clean-Catch Urine Collection Procedure For 1.Wash hands thoroughly. Men 2. Remove lid of container without touching inside of cover or container 3. Wash end of penis with special wipe beginning at urethral opening and working away in a circular motion. (Foreskin must be retracted) 4. Keeping foreskin retracted, if applicable, void into the toilet for a few seconds. 5. Touching only outside of container, bring container into urine stream until sufficient amount is collected (30-100 mL) 6. Void any additional urine into toilet. 7. Screw on lid, only touching outer surfaces. 8. Clean any urine off of outside of container using antiseptic wipe.  Suprapubic Aspiration Specimen is obtained by placing a needle through the abdomen into the bladder. Provides a sample free from contamination for bacterial culture. Can also be used for cytologic examination.  Pediatric Specimens Collected using soft, clear plastic bags attached to the infant’s genital area. When enough urine has been collected, the bag is removed and the specimen is poured into a container. Specimens can also be collected by: Catheterization Suprapubic aspiration