Skip to content
SearchProgress
Display

Display

Theme
Density
Text size

Sign in

Add your earlier progress to your account?

Study progress is waiting to be saved

Urine specimens and storage

15 min

  • Decide whether a urine specimen meets the requested test's requirements
  • Predict changes caused by delayed urine examination
  • Select a urine collection type suited to the requested measurement

Read the full reference

Try first

Try first

A urinalysis and a urine culture are ordered on one specimen. It arrives 30 minutes after collection in a clean, nonsterile routine cup, labeled on the container body. What do you do?

The next section explains it.

The next section explains it.

Right. The next section explains why.

The next section explains it.

Get the idea

Check the specimen before you test

Each laboratory writes its own rejection criteria. The common reasons to reject a urine specimen are:2

  • a missing, illegible or mismatched label, or a label on the lid only
  • visible fecal or tissue-paper contamination
  • too little urine for the ordered tests
  • an unpreserved specimen past the laboratory's stability limit
  • a culture specimen in a nonsterile container
  • a collection method that does not fit the ordered test

The collector labels the container body in the patient's presence, because a lid can be removed or exchanged.2 A fixed-dose boric-acid culture tube is filled to its line. Underfilling raises the preservative concentration, which can inhibit organisms and give a falsely low or negative culture.4

Match the collection to the test

  • Random: routine urinalysis and screening.
  • First morning: the concentrated void after overnight recumbency, for low-concentration constituents and orthostatic proteinuria.
  • 24-hour: total daily excretion.
  • Midstream clean-catch: routine urinalysis and culture.
  • Catheterized or suprapubic: culture when a voided specimen is unsuitable.
  • Pediatric bag: screening urinalysis only. Perineal flora contaminate it, so a positive bag culture cannot establish infection.2

What a delay does

College of American Pathologists (CAP) requirements direct accredited laboratories to examine urine within 2 hours of collection unless it is refrigerated or chemically preserved.3 Unpreserved urine at room temperature changes in predictable directions:1

ResultAfter a delayWhy
pHRisesBacteria convert urea to ammonia
TurbidityRisesBacteria grow and crystals form
NitriteRisesBacteria reduce nitrate
GlucoseFallsCells and bacteria consume it
KetonesFallAcetoacetate degrades and acetone evaporates
Bilirubin and urobilinogenFallLight oxidizes them
Intact cells and castsFallThey lyse, faster in dilute or alkaline urine

When several of these changes appear together in a late specimen, the results describe the storage. Request a fresh specimen and record the reason. Refrigeration slows the changes and can precipitate amorphous urates and phosphates that cloud the sediment.1,2

References
  1. Kouri TT, Hofmann W, Falbo R, et al. The EFLM European urinalysis guideline 2023. Clin Chem Lab Med. 2024;62(9):1653-1786. doi:10.1515/cclm-2024-0070
  2. Clinical and Laboratory Standards Institute. Processes for the Collection of Urine Specimens. 1st ed. CLSI guideline PRE05. Clinical and Laboratory Standards Institute; 2024. Accessed September 27, 2026. https://clsi.org/shop/standards/pre05/
  3. College of American Pathologists. Urinalysis Checklist. December 9, 2025 ed. Requirement URN.22300. Accessed September 27, 2026. https://www.cap.org/laboratory-quality-solutions/accreditation/accreditation-checklists/
  4. UK Health Security Agency. Diagnosis of urinary tract infections: quick reference tools for primary care. Updated July 7, 2025. Accessed September 27, 2026. https://www.gov.uk/government/publications/urinary-tract-infection-diagnosis/diagnosis-of-urinary-tract-infections-quick-reference-tools-for-primary-care

Watch one

An outpatient urine arrives at the urinalysis bench at 12:20. The label says it was collected at 07:40, and the cup is at room temperature.

What do these results describe?

TestResultPreviousReference intervalFlag
pH8.54.5–8.0High
NitritePositiveNegative
Leukocyte esteraseSmallNegative
GlucoseNegativeNegative
WBC0–2 /hpf0–5 /hpf
BacteriaManyNone seen

Specimen: Not measured on urine. Random urine, collected 07:40, received 12:20 unrefrigerated

  1. Check the collection time first: 4 hours 40 minutes at room temperature, well past the 2-hour limit for unpreserved urine.

    Time and temperature decide whether the urine still matches what the patient passed.

  2. Read the pH: 8.5 is higher than fresh urine usually runs and fits bacterial growth after collection.

    Bacteria growing in the cup make ammonia from urea, which pushes the pH up.

  3. Read the nitrite with the bacteria: many bacteria and a positive nitrite can both come from hours of growth in the cup.

    Nitrite keeps forming as long as bacteria sit with the urine's nitrate.

  4. Compare the leukocyte esterase with the count: a positive pad with 0–2 WBC/hpf fits white cells that lysed in alkaline urine.

    The esterase pad reacts with enzyme from lysed white cells that microscopy can no longer count.

  5. Decide: the pattern describes the delay, so request a fresh specimen and record the late, unrefrigerated arrival as the reason.

    Retesting the same urine only repeats what the storage did.

The results show deterioration during 4 hours 40 minutes at room temperature. None of them can be reported as the patient's urine, and a fresh specimen is needed.

Your turn

Problem 1 of 3

Bacteria grow from a pediatric bag urine culture. What should happen next?

Correct. Perineal flora frequently contaminate bag specimens and can grow from outside the urinary tract, so diagnostic culture needs urine collected by catheterization or suprapubic aspiration.

Incorrect. Perineal flora can grow to high counts in a bag specimen, so bag growth cannot establish a urinary tract infection at any colony count.

Incorrect. A second bag specimen carries the same perineal contamination. Diagnostic culture needs catheterized or suprapubic urine.

Hint
  1. Think about what the bag touches while it collects.
  2. Ask which collections take urine straight from the bladder.

Review Routine collections

Problem 2 of 3

A fixed-dose boric-acid urine culture tube is substantially underfilled. Why can this affect culture recovery?

Correct. The tube holds a fixed boric-acid dose sized for its fill line, so less urine raises the concentration enough to inhibit organisms and produce a falsely low or negative culture.

Incorrect. The number of organisms per milliliter does not depend on how much urine enters the tube. The problem is the higher preservative concentration.

Incorrect. Boric acid is meant to hold counts stable. In an underfilled tube its excess concentration inhibits organisms and lowers recovery.

Hint
  1. The tube holds the same amount of boric acid however much urine goes in.
  2. Work out what less urine does to the preservative's concentration.

Review Refrigeration and preservatives

Problem 3 of 3

An unpreserved urine sat for 5 hours on a counter under room lights before testing. Which result is most likely to read falsely low?

Bacteria keep converting urea to ammonia during the delay, so the pH rises.

Bacteria keep reducing nitrate in the cup, so nitrite tends to rise with time.

The pads measure the urine as it is now. After 5 hours, that urine no longer matches what the patient passed.

Interpreted storage changes as the original specimen state

After hours at room temperature, bacteria raise pH and nitrite, cells and casts lyse, glucose falls, and bilirubin fades in light. Reporting these changes as the patient's urine gives falsely alkaline, nitrite-positive, cell-poor results. The specimen needs a fresh collection.

Light oxidizes bilirubin and the delay adds to the loss, so the pad can read low or negative.

Review Changes during storage

Use it

  • Dana Okafor, 17, had protein on a sports physical dipstick.
  • Orders: routine urinalysis, urine culture, and a urine protein check on a first morning specimen for orthostatic proteinuria.
  • One sterile cup arrives at 16:05, labeled on the body: midstream clean-catch, collected 15:20.
  • The cup stayed at room temperature.
Decision 1 of 3

Can the routine urinalysis and the culture go ahead on this cup?

A midstream clean-catch collection in a sterile cup is a standard culture specimen for an adolescent who can provide one.

The cup is sterile and labeled on the body, and it arrived 45 minutes after collection, inside the 2-hour limit for unpreserved urine.

Routine urinalysis and culture accept a random midstream void. The time of day matters for the protein check.

Review Acceptability

Decision 2 of 3

What do you do about the orthostatic protein check?

A 24-hour collection mixes upright and recumbent urine, so it cannot separate the two.

This void follows a day of upright activity, when orthostatic protein appears. It cannot show whether protein clears during recumbency.

Assumed one urine specimen suits every test

A random void cannot show 24-hour excretion, a later void cannot replace the first morning void in an orthostatic protein check, and a bag specimen cannot support a diagnostic culture. The wrong collection gives a valid-looking result that does not measure what was ordered.

That void collects urine formed while recumbent overnight, which is the specimen the check depends on.

Review Routine collections

Decision 3 of 3

The urinalysis is set aside by mistake and found at 18:50, still at room temperature. What do you do?

At 3 hours 30 minutes unrefrigerated, pH, nitrite, glucose and cell counts may describe the storage. A fresh specimen gives results that describe Dana's urine.

A comment cannot tell a reader which results changed or by how much.

Refrigeration slows further change. It cannot undo the changes that happened during the delay.

Past the 2-hour limit, the results can show bacterial growth and cell lysis that happened in the cup.

Interpreted storage changes as the original specimen state

After hours at room temperature, bacteria raise pH and nitrite, cells and casts lyse, glucose falls, and bilirubin fades in light. Reporting these changes as the patient's urine gives falsely alkaline, nitrite-positive, cell-poor results. The specimen needs a fresh collection.

Review Changes during storage

The clue that settled this case is the collection time on the label. It showed the cup was fit for urinalysis and culture on arrival, unfit for a check that needs the overnight first void, and too old for urinalysis once it had waited past 2 hours.

Keep

Sources checked