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Basic Examination of the Urine Specimen
Phlebotomy and
Medical Laboratory Technology Program FacultyAustin Community College
Introduction
• All specimens must be properly labeled– The laboratory request slip must
accompany the specimen • The patient’s name • The patient’s identification number • The date • The time of collection • The type of specimen • The attending physician’s name • The label should be affixed on the container, not the lid.
The Urine Sample
• Collection and Preservation of Urine – Types of Specimens & Containers
Urine collected anytime of the day or night can be used for routine urinalysis testing, BUT the sample collected the first thing in the morning is preferred as it is the most concentrated.
Containers must be clean and single use (disposable). If urine is to be cultured for bacteria, the container must
be sterile.
Sample cup for routine testing
The Urine Sample
• Collection and Preservation of Urine – Types of Specimens
When special tests, usually performed in the chemistry department are ordered, the urine sample is usually collected over a 24 hr. period of time.
24 hour urine collection container.
The Urine Sample
• Handling and preserving specimens – Urine samples must be examined within 1 hour of
collection OR be refrigerated.– For routine testing, the refrigerated sample must
be tested within 8 hours.
– Never leave a urine sample sitting out at room temperature more than 1 hour.
Bacterial growth in the sample destroy or change important chemicals and elements.
– Color of urine Yellow –Some shade of ‘yellow’ is the typical
color of urine.• dilute urine is usually lighter in color; concentrated
urine is usually dark• Urochrome – pigment that gives urine its yellow color• Certain foods, supplements, prescription drugs, etc.
may cause harmless temporary changes in urine color.
• Most common colors– Light yellow (may be called pale yellow or straw)– Yellow– Dark yellow
Testing the Urine Sample
– Other colors of urine May or may not indicate a disease process
• Amber – a deep yellow-brown or green-brown color. Although not always pathological, often associated with increased bilirubin and seen in liver conditions such as hepatitis or cirrhosis.
• Red – may have blood present• Brown/black – may be associated with melanoma• Port wine color – result of a ‘porphyria’ - a rare
metabolic condition that affects skin and nervous system
• Neon-yellow – often seen in persons taking B vitamins
Testing the Urine Sample
– Urine Clarity or Transparency Refers to how clear is the urine sample Technician swirls the sample in the cup and with
a good background light source, looks through the specimen.
Terms to describe clarity: clear, hazy, cloudy and turbid.• Fresh urine is usually clear to hazy.• Fresh urine that is cloudy often indicates a bacterial
infection (the cloudiness due to presence of white blood cells).
• Things that make urine hazy: mucous, sperm / prostatic fluids, skin cells, urine crystals, & contaminates such as body powders, etc.
Testing the Urine Sample
• Chemical Examination of Urine – Reagent strips
Test pads are for pH, protein, glucose, ketone, bilirubin, blood, urobilinogen, specific gravity, leukocytes and bacteria
Used only once and discarded Performing the chemical tests by reagent strip
• Perform within 1 hour after collection OR• Allow refrigerated specimens to return to room
temperature• Dip strip in fresh urine and compare color of pads to
the color chart after appropriate time period• Instruments are available which detect color changes
electronically
Testing the Urine Sample
– Follow manufacturer’s directions, regardless of whose product you are using
– When reading dipstick results manually; colors are matched to those on the bottle’s
label; timing is critical for each pad.
Testing the Urine Sample
Procedure
• Normal dipstick procedure:– Dip strip briefly, but completely into well
mixed, room temperature urine sample.– Withdraw strip, blot briefly on its side– Keeping the strip flat, read results at the
appropriate times by comparing the color to the appropriate color on the chart provided.
Chemical Exam of Urine
Sources of error (& preventions)– Failure to observe color changes at appropriate time
– Failure to observe color changes under good lighting
– Testing cold specimens would result in a slowing down of reactions; test
specimens when fresh or bring them to RT before testing
– Inadequate mixing of specimen could result in false reduced or negative reactions to
blood and leukocyte tests; mix specimens well before dipping
– Over-dipping of reagent strip will result in leaching of reagents out of pads; briefly,
but completely dip the reagent strip into the urine
• Handling and Storage– Keep strips in original container, stored at RT– Protect from moisture and volatile fumes– Use before expiration date– Do not touch reagent pad areas
Chemical Exam of Urine
• Precautions (again)– Reagent strips should be tested with positive
controls on each day of use– Failure to observe color changes at appropriate
time intervals may cause inaccurate results– Reagents and strips must be stored properly to
retain activity– Observe color changes and color charts under good
lighting– Proper collection and storage of urine is necessary
to insure preservation of chemical and formed elements
Chemical Exam of Urine
• Quality Control - use appropriate, commercially prepared positive and negative controls.– Use commercially prepared pos and neg controls,
at least once per 24 hours, and anytime a new bottle is opened, or question of validity of results. Readings should agree with published results ± one color block.
Chemical Exam of Urine
• Strip readers– Bayer Clinitek automatically reads a
urine dipstick and prints out results
Chemical Exam of Urine
Thoughts about urine chemical tests
– Glucose Presence of glucose (glycosuria) indicates that the blood
glucose level has exceeded the renal threshold This test result is useful to screen for diabetes
Thoughts about urine chemical tests
– Bilirubin Bilirubin is a byproduct of the breakdown of
hemoglobin. Not normally found in the urine. Its presence may be an indication of liver disease, bile
duct obstruction or hepatitis Bilirubin quickly breaks down in light, resulting in false
negative results if the sample is exposed to light for a long period of time.
Thoughts about urine chemical tests
– Ketones are excreted when the body metabolizes fats
incompletely (ketonuria) Ketones evaporate easily and the sample must be kept
tightly capped and tested within an hour of collection for best results.
Thoughts about urine chemical tests
– Specific gravity reflects kidney's ability to concentrate the urine High specific gravity indicates a concentrated sample.
The first morning collection specimen usually has a high specific gravity and provides the most useful urinalysis results.
Low specific gravity indicates the urine is more ‘water-like’.
Thoughts about urine chemical tests
– Presence of blood may indicate infection, trauma to the urinary tract or
bleeding in the kidneys Positive results are also seen due to contamination
with menstrual blood
Thoughts about urine chemical tests
– Protein Presence of protein (proteinuria) is an important indicator of
renal disease False negatives can occur in alkaline or dilute urines or when
the primary protein is not albumin.
Thoughts about urine chemical tests
– Urobilinogen is a degradation product of bilirubin formed by intestinal
bacteria. It may be increased in hepatic disease or hemolytic
disease
Thoughts about urine chemical tests
– Nitrite formed by gram negative bacteria converting urinary
nitrate to nitrite Any shade of pink color on this pad is considered a
positive result.
Thoughts about urine chemical tests
– Leukocytes (white blood cells) A positive leukocyte usually indicate infection,
especially when the nitrite pad is also positive.