basic examination of the urine specimen

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


Examples of Urine Color

– 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.


Examples of Urine Clarity/Transparency

• 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


• Urine Multistix – This product made by Siemans Bayer

corp.


• Chemstrip Urine Test Strips– This product is made by Roche-Diagnostics


– 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.


Chemical Exam of UrineMultistix

•

Chemical Exam of Urine

•

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.


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


• 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


• 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.


• Strip readers– Bayer Clinitek automatically reads a

urine dipstick and prints out results


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


– 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.


– 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.


– 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’.


– 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


– pH measures degree of acidity or alkalinity of urine


– 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.


– Urobilinogen is a degradation product of bilirubin formed by intestinal

bacteria. It may be increased in hepatic disease or hemolytic

disease


– Nitrite formed by gram negative bacteria converting urinary

nitrate to nitrite Any shade of pink color on this pad is considered a

positive result.


– Leukocytes (white blood cells) A positive leukocyte usually indicate infection,

especially when the nitrite pad is also positive.


• Normal values– Negative results for glucose, ketones, bilirubin,

nitrites, leukocyte esterase and blood– Protein negative or trace– pH 5.5-8.0– Urobilinogen 0.2-1.0 Ehrlich units

basic examination of the urine specimen

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