Urinalysis Lab Simulation
The Chemical Exam
What is Urinalysis?
Urinalysis is the chemical, physical, and microscopic evaluation of urine. During this simulated exercise, you will first chemically examine a subject’s urine using reagent pads attached to a dipstick. Next, you will macroscopically examine the subject’s urine for its volume, color, clarity, and smell, using only your eyes and nose. Finally, you will microscopically examine the subject’s urine to evaluate its suspended components. You will conclude the exercise by making a diagnostic assessment using the subject’s medical history and data from your results.
Exercise Test Subject
Personal and Medical History
Your subject is 40 years old and works as a consultant from home. For much of her day, she sits in front of a computer and conducts financial transactions.
After moving into a management position, her work schedule increased to a point where it interfered with her exercise routine.
As a result, she gained 50 pounds over the past two years. Your subject also reports urinating frequently and is often hungry, thirsty, and fatigued.
Your subject is visiting your clinic for a physical exam. Her last exam was performed several years ago but indicated she was in good health.
Chemical Exam Background
Introduction
The chemical examination of urine determines the pH and content levels of several clinically significant chemical compounds.
Urine Test Strip
The exam uses commercially prepared test strips to ascertain the condition of the urine. The test strips consist of narrow plastic ribbons with absorbent pads attached to one side. The pads contain chemicals that react and change color after being immersed in urine.
Typically, a single strip can test for leukocytes, nitrites, urobilinogen, proteins, pH, blood, specific gravity, ketones, bilirubin, and glucose.
Diagnostic Color Chart
Manufacturers usually package several urine test strips in a single bottle-like container. On the outside of the bottle is a diagnostic chart consisting of colored squares and associated test values.
After fully immersed in urine, a test strip is positioned next to the color chart. The reagent pad colors are then compared with the corresponding squares on the color chart. Color changes in the test strip pads indicate possible adverse health conditions.
The Chemical Tests and Their Indications
Leukocytes The test pad measures leukocyte esterase in the urine released by white blood cells (WBCs). Elevated levels of urine WBCs (pyuria) indicate a urinary tract infection (UTI).
Nitrites The test pad measures nitrites in the urine that form when an enzyme is released from bacteria. A positive result (nitrituria) indicates a urinary tract infection (UTI).
Urobilinogen The test pad measures urobilinogen in the urine that has entered the urinary tract from the bloodstream. Bacteria in the intestines make urobilinogen from bilirubin, which is in the bile produced by the liver. Elevated levels of urine urobilinogen indicate liver disease and dysfunction.
Proteins The test pad primarily measures urine albumins that have entered the urinary tract from the bloodstream. Elevated urine proteins (proteinuria) indicate kidney disease or immune disorders.
pH The test pad measures urine acidity and alkalinity. The normal pH range is 4.6 – 8.0. Urine that is too alkaline or too acidic may cause crystals and stones to form that can block the urinary tract passageways.
Blood The test pad measures hemoglobin from red blood cells that have entered the urinary tract from the bloodstream. Blood in the urine (hematuria) indicates kidney damage, urinary tract infection (UTI), kidney or bladder stones, kidney or bladder cancer, or blood disorders.
Specific Gravity The test pad measures urine particle concentration. The test value indicates the blood hydration level. Urine with a specific gravity of 1.000 -1.010 indicates overhydration, and urine with a specific gravity of 1.025 – 1.030 indicates dehydration.
Ketones The test pad measures urine ketones that have entered the urinary tract from the bloodstream. Ketones are produced in the liver from the breakdown of fats when glucose is not available to the cells for energy. Elevated levels of urine ketones (ketonuria) usually indicate type 1 or 2 diabetes mellitus. An accumulation of ketones in the blood can lead to ketoacidosis.
Bilirubin The test pad measures bilirubin in the urine that has entered the urinary tract from the bloodstream. Bilirubin is produced by the liver during the breakdown of heme from RBCs and then released in the bile. Elevated levels of urine bilirubin (bilirubinuria) indicate liver disease or blockage of the bile duct.
Glucose The test pad measures urine glucose that has entered the urinary tract from the bloodstream. Glucose enters the urine when the blood glucose exceeds ~ 180 mg/dL. Normal blood glucose is 99 mg/dL or below, and elevated urine glucose levels (glucosuria) usually indicate type 1 or 2 diabetes mellitus.
Chemical Exam Procedure
Immerse Urine Test Strip
Obtain a test strip and slowly submerge it into the urine sample, ensuring you cover each test strip square’s surface.
Once it’s saturated, remove the test strip from the urine container and turn it horizontally. In this position, any excess urine will drain away and ensure that the reactive chemicals don’t run from one square to another.
Before determining the results, wait 2 minutes for all the reactions to finish.
Chemical Exam Results
Read Test Strip
Compare the test squares to the standardized color chart to determine if any abnormalities are present. Read the test strip squares in chronological order. Check the value of the last pad (30 sec. read time), then move on to the next pad until you’ve reviewed the entire strip.
Report your finding using quantitative or semi-quantitative values. The values included in a quantitative report use standardized numerical units, such as g/l, mmol/l, and μmol/l. In comparison, the values in a semi-quantitative report use non-standardized units, including Trace, 1+, 2+, 3+, and 4+.
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References and Attributions
Labpedia – Urine Analysis: Physical Examination, and Interpretation
Kaiser Permanente – Urine Test
Clevland Clinic – Proteinuria
Medline Plus – Bilirubin in Urine
Medline Plus – Urobilinogen in Urine
Mount Sinai – Urine pH
NIH National Library of Medicine – Bilirubinuria
UCSF Diabetes Education Online – Ketones
University of California San Francisco Health – Urine Specific Gravity
The University of Utah – Urinalysis