WEEK 1 - Introduction to Urinalysis 3

What is the preferred urine specimen for routine urinalysis?

First morning urine

What is the collection technique for the preferred urine specimen?

Midstream clean-catch

What type of container should be used for urine specimen collection?

Clean, dry, leak-proof, transparent, wide-mouthed container with a capacity of 50 mL

What information must be included on the urine specimen label?

Patient's full name, date and time of collection

What additional information may be included on the urine label?

Patient’s age and sex

What must be submitted along with the urine specimen?

A properly filled-out request form

Within how long should urine specimens be transported and processed?

Within 2 hours after collection

What are grounds for specimen rejection?

Unlabeled, mislabeled, contaminated, insufficient, or improperly transported specimens

What should be done if urine specimen processing is delayed?

Preserve the specimen

What are the two main preservation methods for urine specimens?

Physical preservation and refrigeration (~4°C)

What is a disadvantage of refrigeration as a preservative?

Precipitates amorphous phosphates and urates

How long does refrigeration prevent bacterial growth in urine specimens?

Up to 24 hours

What is an advantage of refrigeration for urine specimens?

Does not interfere with chemical tests

What does formalin preserve well in urine specimens?

Sediment

What is a disadvantage of using formalin as a preservative?

Interferes with tests for glucose, blood, leukocyte esterase, and copper reduction

How should formalin be used in urine specimen preservation?

Rinse the specimen container with formalin

What is an advantage of sodium fluoride as a urine preservative?

Preserves glucose and is good for drug analysis

What is a disadvantage of sodium fluoride?

Inhibits reagent strip tests for glucose, blood, and leukocyte esterase

What is an advantage of acid preservatives (e.g., boric acid, HCl, acetic acid)?

Prevents bacterial growth and metabolism

What is a disadvantage of acid preservatives?

Interferes with drug and hormone analysis

What pH is maintained by acid preservatives in urine specimens?

Approximately pH 6.0

When can acid preservatives be used for urine specimens?

For transport of urine cultures

What is an advantage of commercial preservative tablets?

Convenient when refrigeration is not possible

What precaution should be taken when using commercial preservative tablets?

Check the tablet’s composition for possible test interference

What disadvantage is common to formalin, sodium fluoride, and acid preservatives?

They may interfere with chemical or strip tests

What is the urine preservative in the Light Gray and Gray C&S tube?

Boric acid, sodium borate, and sodium formate

How long is the specimen stable at room temperature in the Light Gray and Gray C&S tube?

48 hours

What is the main function of the Light Gray and Gray C&S tube preservatives?

Prevents bacterial growth and metabolism

When should the Light Gray and Gray C&S tube not be used?

If urine is below the minimum fill line

What is the approximate pH maintained by the Light Gray and Gray C&S tube?

About pH 6.0

What type of instruments is the Yellow UA Plus tube used for?

Automated instruments

What is the storage requirement for the Yellow UA Plus tube?

Must be refrigerated within 2 hours

Does the Yellow UA Plus tube contain a preservative?

No, it contains no preservative

What is the shape of the Yellow UA Plus tube?

Round or conical bottom

How long is the specimen stable at room temperature in the Cherry Red/Yellow Preservative Plus tube?

72 hours

What is required when using the Cherry Red/Yellow Preservative Plus tube?

Must be filled to the minimum fill line

What may happen if the Cherry Red/Yellow Preservative Plus tube is exposed to light and left at room temperature?

Decrease in bilirubin and urobilinogen

What preservatives are used in the Cherry Red/Yellow Preservative Plus tube?

Sodium propionate, ethyl paraben, and chlorhexidine

What is the shape of the Cherry Red/Yellow Preservative Plus tube?

Round or conical bottom

What makes the Cherry Red/Yellow Preservative Plus tube suitable for lab instrumentation?

It is instrument compatible

What causes the color of unpreserved urine to darken or change?

Oxidation or reduction of metabolites

What causes the odor of unpreserved urine to become ammoniacal?

Bacterial multiplication causing breakdown of urea to ammonia

Why does the pH of unpreserved urine increase over time?

Breakdown of urea to ammonia and loss of CO2

What causes an increase in nitrite in unpreserved urine?

Multiplication of nitrate-reducing bacteria

Why do bacteria increase in unpreserved urine?

Multiplication over time

Why does the clarity of unpreserved urine decrease (become more turbid)?

Bacterial growth and precipitation of amorphous material

Why does glucose decrease in unpreserved urine?

Glycolysis and bacterial use

Why do ketones decrease in unpreserved urine?

Volatilization and bacterial metabolism

Why does bilirubin decrease in unpreserved urine?

Oxidation to biliverdin when exposed to light

Why does urobilinogen decrease in unpreserved urine?

Oxidation to urobilin

Why do RBCs and WBCs decrease in unpreserved urine?

Disintegration in dilute alkaline urine

Why do Trichomonas organisms decrease in unpreserved urine?

Loss of motility and death