Specimen Collection and Handling
Specimen Handling and Acceptability
How collection, labeling, storage, and preservation determine whether a urine specimen is suitable for testing.
Reliable urinalysis begins with correct patient identification, collection, transport, and storage. Errors during these steps may make a specimen unsuitable for testing or alter the results before analysis begins.
Container and volume
Routine urinalysis specimens are collected in wide-mouthed, flat-bottomed, clear containers with secure closures. A typical container holds about 50 mL. The volume needed for sediment examination depends on the laboratory’s method; many methods use approximately 12 mL. Enough urine should be available for the requested tests and any repeat analysis. Screw caps are less likely to leak during transport than snap caps. Specimens submitted for culture require a sterile container, because a nonsterile container makes the culture unacceptable even when the collection technique was otherwise adequate.
Acceptability
The container should be labeled in the patient’s presence at the time of collection. Place the label on the container rather than the lid, because lids can be removed or exchanged.
Each laboratory defines its own specimen rejection criteria. Common reasons for rejection include:
| Reason | What it puts at risk |
|---|---|
| Missing, illegible, or mismatched label | Patient identification; the result cannot be assigned reliably |
| Visible fecal or tissue-paper contamination | Chemical and microscopic results, as well as culture |
| Volume too low for the ordered tests | Completion of the requested tests and any repeat analysis |
| Unpreserved and delayed past the laboratory’s limit | Stability of pH, cells, casts, glucose, and bilirubin |
| Culture ordered, nonsterile container | The culture result; routine urinalysis may still be reportable |
| Collection method wrong for the order | Interpretation of timed or localization studies |
The collection method must also match the purpose of the test. A random specimen may be suitable for routine urinalysis, but it cannot be used to assess 24-hour excretion.
What changes while a specimen waits
Urine begins to change after collection. Bacterial growth, oxidation, exposure to light, loss of volatile compounds, and cell lysis can alter chemical and microscopic findings. These changes often occur in characteristic directions, so a combination of results may indicate that a specimen was delayed or stored improperly.
| Measurement | Direction after delay | Mechanism |
|---|---|---|
| pH | Rises | Urea to ammonia |
| Clarity | Falls (more turbid) | Bacterial growth, crystal formation |
| Color | Darkens | Pigment oxidation |
| Glucose, ketones | Fall | Consumed by bacteria and cells; ketones also volatilize |
| Bilirubin, urobilinogen | Fall | Photo-oxidation on standing in light |
| Nitrite | Rises | Bacterial reduction of nitrate |
| RBCs, WBCs, casts | Fall | Lysis, especially in dilute or alkaline urine |
A high pH, increased turbidity, positive nitrite, and loss of intact cells may occur together in a specimen that remained at room temperature for several hours.
CAP-accredited laboratories examine urine within two hours of collection unless the specimen is refrigerated or chemically preserved. This is an accreditation requirement rather than a general rule of thumb.
Worked example. A specimen arrives several hours after collection, unrefrigerated, with a high pH, heavy turbidity, a positive nitrite result, and no intact cells on microscopy. The combined findings are consistent with deterioration during the delay. A fresh specimen should be requested rather than interpreting the pattern as the patient’s current condition.
Refrigeration and preservatives
Refrigeration is preferred when testing cannot be completed within the allowed time because it introduces no chemical preservative. It can, however, cause amorphous urates and phosphates to precipitate and obscure the sediment. Warming can redissolve urates, and acidification can redissolve phosphates, but neither treatment reliably restores a preparation that has become uninterpretable. A fresh specimen should be requested when precipitate prevents particle identification.
Preservatives affect different tests in different ways, so the preservative must be selected for the requested testing. Boric-acid transport systems maintain bacterial counts for culture. Hydrochloric acid is used for selected quantitative chemistry collections and is unsuitable for culture. The preservative must be chosen before transport because it cannot be removed after it has been added.
References
- Kouri TT, Hofmann W, Falbo R, et al. The EFLM European Urinalysis Guideline 2023. Clin Chem Lab Med. 2024;62(9):1653-1786.
- Clinical and Laboratory Standards Institute. Processes for the Collection of Urine Specimens. 1st ed. CLSI guideline PRE05. CLSI; 2024.
- College of American Pathologists. Urinalysis Checklist, 12/09/2025 edition. Requirements URN.22300 and URN.22400. A CAP accreditation requirement, not a regulation.