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 ...
- Chemically examine the subject's urine using reagent pads on a dipstick.
- Macroscopically examine the subject's urine for volume, color, clarity, and odor, using only your eyes and nose.
- Microscopically examine the subject's urine to evaluate its suspended components.
- Make a diagnostic assessment using the subject's medical history and your results.
Exercise Test Subject
Personal and Medical History
Your subject is 40 years old and works as a home-based consultant. For much of the day, she sits at a computer and processes financial transactions.
After moving into a management position, her work schedule became so demanding that 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.
Exam Background Information
Introduction
The chemical examination of urine determines the pH and concentrations of several clinically significant compounds.
The Urine Test Strip
The exam uses commercially prepared test strips to ascertain the condition of the urine. The test strips contain narrow plastic ribbons with absorbent pads attached to one side. The pads contain chemicals that react with urine and change color.
Typically, a single strip can test for leukocytes, nitrites, urobilinogen, proteins, pH, blood, specific gravity, ketones, bilirubin, and glucose.
Urine Test Strip
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 with colored squares and corresponding test values.
After being fully immersed in urine, a test strip is positioned next to the color chart. The reagent pad colors are compared with the corresponding squares on the color chart. Color changes in the test strip pads indicate possible adverse health conditions.
Chemical Tests and Indications
Leukocytes This test pad detects leukocyte esterase, an enzyme produced by white blood cells (WBCs). Elevated levels of WBCs in the urine (pyuria) typically indicate a urinary tract infection (UTI) or inflammation.
Nitrites This test pad detects nitrites, which are produced when urinary tract bacteria (such as E. coli) convert normal urinary nitrates into nitrites. A positive result (nitrituria) typically indicates a bacterial urinary tract infection (UTI).
Urobilinogen This test pad detects urobilinogen, which intestinal bacteria make from bile bilirubin. Some urobilinogen enters the blood and is filtered into urine. Small amounts are normal, but elevated levels (urobilinogenuria) indicate liver disease or excessive red blood cell breakdown, while an absence indicates a blocked bile duct.
Proteins This test pad primarily detects albumin, a major blood protein. Healthy kidneys normally prevent large proteins from filtering into urine. Elevated protein levels (proteinuria) typically indicate kidney disease or damage to the kidney's filtration membrane.
pH This test pad measures urine acidity and alkalinity, indicating how well the kidneys are maintaining acid-base balance. Normal urine pH ranges from 4.6 to 8.0. Persistently abnormal pH levels can promote the formation of crystals and kidney stones.
Blood This test pad detects hemoglobin from intact or hemolyzed red blood cells. Blood in the urine (hematuria) typically indicates damage to the kidney's filtration membrane, urinary tract infection (UTI), urinary stones, or physical trauma to the kidneys or bladder.
Specific Gravity This test pad measures urine concentration compared to pure water (1.000). The value indicates how effectively the kidneys regulate hydration and blood concentration. Normal values typically range from 1.005 to 1.030. Low values indicate dilute urine (overhydration), while high values indicate concentrated urine (dehydration).
Ketones This test pad detects ketones, which the liver produces during fat metabolism when cells cannot use glucose for energy. Elevated urine ketones (ketonuria) typically indicate uncontrolled diabetes mellitus (especially type 1), prolonged fasting, or starvation. High blood ketone levels can lead to life-threatening ketoacidosis.
Bilirubin This test pad detects bilirubin, a waste pigment produced by the liver when it breaks down hemoglobin released by red blood cells. Bilirubin is normally eliminated in bile, so its presence in urine (bilirubinuria) indicates liver disease, hepatitis, or a blocked bile duct.
Glucose This test pad detects glucose in the urine. Healthy kidneys normally reabsorb all filtered glucose back into the blood. When blood glucose is too high (~180 mg/dL), the kidneys cannot reabsorb it all, and the excess spills into the urine (glucosuria), which typically indicates uncontrolled diabetes mellitus.
Exam Procedures
Immerse Urine Test Strip
Obtain a test strip and slowly submerge it into the urine sample, ensuring you cover all the pads on the test strip.
Once saturated, remove the test strip from the urine container and turn it horizontally. Any excess urine will drain away in this position, ensuring the reactive chemicals don't run from one square to another.
Before determining the results, wait 2 minutes for all the reactions to finish.
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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 findings using quantitative or semi-quantitative values.
The values in a quantitative report are expressed in 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
Cleveland 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