SPECIMEN COLLECTION AND URINE SPECIFIC GRAVITY MLS 112 - AUBF - LABORATORY PRELIM

What are the 4 major rules of urine specimen collection and handling?

• Collect in clean, dry, leak-proof containers.

• Use wide-mouth, flat-bottom, screw-top containers (50 mL).

• Properly label with patient’s name, ID, date/time, age, location, and physician’s name.

• Deliver promptly and test within 2 hours.

What must be included on a urine specimen label?

Patient’s name, ID number, date/time of collection, age, location, and physician’s name.

What are common reasons for urine specimen rejection?

Unlabeled containers, mismatched labels, contamination with feces or toilet paper, dirty container exterior, insufficient quantity, improper transport, poor preservation, nonsterile container for culture, or inappropriate collection type.

What is the most common urine specimen preservation method and its temperature range?

Refrigeration at 2–8°C.

Name one disadvantage of urine refrigeration and its remedy.

Can cause precipitation of amorphous urates/phosphates, obscuring microscopic sediment. Remedy: Return specimen to room temperature before testing.

Give two examples of chemical urine preservatives.

Toluene (preserves ketones/proteins but not bacteria) and Thymol (preserves sediment elements, inhibits bacterial/yeast growth).

What is the ideal characteristic of a urine preservative?

Bactericidal, inhibits urease, preserves formed sediment elements, and does not interfere with chemical tests.

What is a random urine specimen used for?

Routine screening tests to detect obvious abnormalities.

Why is the first morning urine specimen preferred?

It is concentrated, improving detection of chemicals and formed elements, preventing false-negative pregnancy tests, and useful for orthostatic proteinuria evaluation.

Describe the 2-hour postprandial urine test procedure and its use.

Void before eating, collect urine 2 hours after eating; used to monitor glucose levels in diabetic patients.

What is the purpose of a 24-hour urine specimen?

For accurate quantitative measurement of substances that vary throughout the day.

What is the main use of a catheterized urine specimen?

Bacterial culture, sometimes for kidney function testing.

What is the midstream clean-catch method used for?

Bacterial culture and urinalysis with minimal contamination.

What urine collection method ensures no contamination?

Suprapubic aspiration.

What is the purpose of the three-glass urine collection method?

To detect prostatic infection.

In drug testing, what does COC stand for and what is its purpose?

Chain of Custody – ensures specimen identity and prevents tampering.

What urine temperature range is acceptable in drug specimen collection?

32.5°C–37.7°C.

Define specific gravity in urine testing.

The density of urine compared with distilled water (1.000) at similar temperature.

What are the three main methods to measure urine specific gravity?

Urinometer, refractometer, and reagent strip.

What is the principle of a refractometer?

Measures refractive index—the change in velocity of light in air vs. a solution.

What method uses sound frequency to measure urine density?

Harmonic oscillation densitometry.

What must be recorded on the requisition form for urine specimens?

Time the specimen is received in the lab, and all information must match the specimen label.

Why must urine specimens be tested within 2 hours if unpreserved?

To prevent physical, chemical, and microbiological changes that can alter results.

Name one disadvantage of toluene as a urine preservative.

Not effective against bacteria already present in urine.

What does sodium carbonate preserve in urine?

Stabilizes porphyrins and porphobilinogen, but is unacceptable for urinalysis.

What is the recommended urine volume for a container used in specimen collection?

50 mL.

In 24-hour urine collection, why must the patient begin and end with an empty bladder?

To ensure the specimen only represents urine produced during the collection period.

Which urine specimen type is essential for preventing false-negative pregnancy tests?

First morning specimen.

In midstream clean-catch for males, what specific cleansing step is required?

Clean the glans starting at the urethra, retract foreskin if necessary.

What method is considered an alternative to catheterized urine collection?

Midstream clean-catch.

What procedure is performed in three-glass urine collection after the midstream sample?

Prostate massage to pass prostatic fluid with the remaining urine.

How much urine is required for a witnessed drug specimen collection?

30–45 mL in a 60 mL container.

What should be done if a drug-test urine specimen temperature is out of range?

Record temperature, notify supervisor/employer, and recollect a second specimen ASAP.

What two factors influence urine specific gravity readings?

Number and size of particles in urine.

Why is a urinometer less accurate compared to other SG methods?

Requires large volume (10–15 mL) and is affected by temperature and large molecules.

How should a urinometer reading be taken?

At the bottom of the urine meniscus.

Why is temperature correction needed for urinometer readings?

Urinometers are calibrated for distilled water at a specific temperature.

What is the main advantage of a refractometer over a urinometer?

Requires only 1–2 drops of urine and no temperature correction.

What does harmonic oscillation densitometry measure in urine testing?

Density changes based on sound wave frequency.