9.2 Urine Suitability, Storage, Preservatives, and Rejection

CMLA II.4.A.2 requires you to recognize the suitability of urine for the procedures ordered: the test requested, patient preparation and method of collection, time of collection and processing, specimen storage, and rejection criteria. II.4.A.5.a adds types and uses of urine preservatives. PRE05's quality-assessment chapters (urinalysis and chemistry, microbiology and molecular, toxicology, cytology) make the same point: a cup that is perfect for one assay can be worthless for another. You are not a chemist inventing a new recipe. You compare the specimen in front of you with the directory and the SOP.

Quick Answer: Match the cup to the test. Unpreserved routine UA is tested promptly—commonly within 2 hours—or refrigerated. Boric acid is a common culture preservative; HCl is an example for some 24-hour chemistries. Follow the label. Reject unlabeled, leaked, insufficient, wrong-type, delayed unrefrigerated, and fecally contaminated urine.

Suitability starts with the test requested

Suitability means this specimen, in this container, collected this way, arriving now, can validly support the ordered test. It is not "the cup has liquid in it."

• Routine UA (macroscopic dipstick ± microscopic) usually needs a clean, preferably mid-stream or first-morning, unpreserved cup delivered promptly. A gray-top boric acid culture tube is the wrong aliquot for many reagent-strip reactions; boric acid can distort pH and other pads. If culture and UA are both ordered, follow the SOP: often a sterile cup for UA plus a transferred preservative tube for culture, not one tube for both.
• Culture (C&S) needs a clean-catch (or catheter) specimen in a sterile container, then either prompt plating, refrigeration, or transfer into a boric-acid transport tube. A random hat from a bedpan is not suitable.
• 24-hour chemistry needs the complete timed volume in the laboratory-issued jug with the stated preservative or refrigeration. A random cup labeled "24-hour" is not a 24-hour specimen.
• Drug screen / toxicology needs the chain-of-custody kit, volume, and temperature documentation (Section 9.1). An open leftover UA is not suitable.
• Cytology (if your laboratory receives it) often has its own fixative and timing; do not pour cytology urine into a UA tube because "urine is urine."

If two tests conflict (acid jug versus no-preservative jug, culture tube versus strip UA), do not mix them. Issue two collections or split before a preservative is added, exactly as the directory says.

Patient preparation and method of collection

Preparation is part of suitability. A beautifully labeled jug collected with three missing voids is still wrong.

Ask—and document per SOP—whether the patient:

• Cleansed and collected mid-stream if culture was ordered.
• Discarded the first morning void and saved the rest for a timed collection, including the stop-time void.
• Followed any directory holds (for example, some 24-hour tests pause certain vitamins or foods; some older occult-blood cards have diet rules—those are stool, Section 9.3, but the habit is the same: read the prep sheet).
• Used the laboratory jug, not a household jar.
• Avoided contaminating the specimen with toilet water, toilet paper, soap, or feces.

If the patient says "I forgot a few times and just filled it this morning," the 24-hour collection is not suitable. Recollect. Do not "average" the volume.

Time of collection and processing

Unpreserved urine is a living, changing fluid. Delay at room temperature lets bacteria multiply and cells fall apart. Classic teaching, aligned with CLSI urine-culture practice, is:

• Unpreserved UA: examine promptly, commonly within 2 hours of voiding. If you cannot, refrigerate (typically 2–8°C) and test as soon as possible. Do not freeze routine UA unless the SOP for a specific analyte says so; freezing lyses cells and destroys formed elements.
• Unpreserved culture: plate within about 2 hours, or refrigerate (often acceptable up to about 24 hours per many procedures), or transfer into a boric acid transport tube when the SOP uses that device. Unpreserved urine sitting warm on a counter for half a day is not a colony count; it is overgrowth.
• Timed collections: the clock is the specimen. Write start and stop times on the jug. Processing includes measuring total volume before any aliquot is removed.

What delay does to unpreserved urine (why the 2-hour rule exists):

Storage and preservatives: examples, then the label

Refrigeration is the default "preservative" for many UA specimens when testing will be delayed. It slows bacterial growth without adding a chemical that can wreck a dipstick.

Chemical preservatives are test-specific. II.4.A.5.a asks you to know types and uses, not to recite an unmatched encyclopedia. Teach two high-yield examples and then follow the SOP and the container label:

• Boric acid (often in a gray-top or similar urine C&S transport tube): used to stabilize culture specimens for transport so bacterial counts do not explode. Fill to the line; underfill concentrates the preservative. Do not automatically use that aliquot for reagent-strip UA. Boric acid can interfere with some pads.
• Hydrochloric acid (HCl) : an example acid used in some 24-hour chemistry collections (selected calcium or other analyte protocols per the receiving laboratory). It is corrosive. Warn the patient. If the jug already contains acid, many SOPs have the patient void into a clean cup and pour, not splash onto the acid. HCl is not the culture preservative.

Other labeled 24-hour additives exist (acetic acid, carbonate/base, boric acid in some chemistry jugs). Do not memorize a private unmatched list and override the catalog. If the jug in your hand does not match the test, do not "make it work" with vinegar, bleach, or a leftover acid from another order.

Never pour urine from a preservative jug back into a no-additive cup to "share" the specimen. Never add a tablet from a different kit because the colors look similar.

Rejection criteria

Reject and document per SOP. Recollect when possible. Do not test a specimen you know is invalid and hope the analyzer flags it.

Classic CMLA rejection reasons:

• Unlabeled (or labeled with only one identifier, or a name that does not match the order). A cup found on the bathroom counter is unlabeled even if you "know" who was just in there. Do not write a name on it after the fact. PRE01 identity rules still apply.
• Leaked or received in a soaked bag: contamination risk, lost volume, and exposure. Transfer is not a salvage if the exterior is contaminated and the volume is unknown.
• Insufficient volume for the tests ordered (or below the fill line of a preservative tube).
• Wrong type: random submitted for culture; acid 24-hour jug submitted for UA dipstick; boric-acid tube submitted as the only UA specimen when the SOP forbids it; household jar; pediatric bag submitted for culture when the SOP requires catheter urine.
• Delayed unrefrigerated unpreserved urine beyond the laboratory's time limit (commonly the 2-hour teaching window).
• Fecal contamination, toilet paper, soap, or obvious debris in a UA or culture cup. Feces in a 24-hour jug also ruins the collection.
• Broken chain of custody or out-of-range temperature on a drug screen.
• Incomplete timed collection (missed voids, wrong clock, dumped volume).

A leaked but still-labeled cup is not automatically acceptable because "there is enough left." An unlabeled cup is not acceptable because the patient is still in the waiting room if the specimen left their sight unlabeled. When in doubt, stop, notify, and recollect.

In practice

You receive a sterile cup of urine for "UA and culture," collected 3 hours ago, left on the clinic counter, with a sticky note but no patient label, and a separate gray-top boric-acid tube that is half empty. You do not dip the unlabeled cup, you do not top off the gray-top from the cup, and you do not run the strip on the boric-acid aliquot just to save a venipuncture-style recollect. You reject, document, and arrange a new clean-catch with immediate labeling, prompt UA, and a filled preservative tube for culture.

Exam traps

• Treating any yellow liquid in a cup as suitable for every urine test.
• Using boric acid as a universal UA preservative, or HCl as a culture preservative.
• Inventing household substitutes for labeled acids.
• Relabeling a bathroom-counter cup.
• Ignoring the 2-hour unpreserved window because the refrigerator was "probably cold enough" after the fact.

When CMLA shows a urine cup, ask five questions: right test, right prep, right clock, right storage, and any rejection flag. If any answer is no, do not process it as a valid specimen.