Will storing a urine specimen in a cold environment affect the accuracy of urinalysis results?

Impact of Cold Storage on Urine Specimen Accuracy

Your urine specimen stored in a cold hospital environment before testing should not significantly affect the accuracy of routine urinalysis results, as refrigeration at 0-4°C is the recommended preservation method when processing is delayed beyond 1 hour. 1, 2

Optimal Storage Conditions

Cold storage (refrigeration) is actually protective for most urinalysis parameters:

• Unprocessed urine should be kept at 0-4°C and processed within 4-8 hours to avoid bacterial growth, cell lysis, molecular degradation of RNA and protein, and formation of sediments 1, 2
• Refrigeration at 4°C prevents bacterial overgrowth more effectively than room temperature storage 1, 2
• Room temperature storage allows only 1 hour maximum before bacterial overgrowth occurs, leading to false-positive results 2
• Refrigerated storage extends this window to 4 hours for reliable urinalysis results 2

Specific Effects of Cold Storage

Most routine urinalysis parameters remain stable with refrigeration:

• Chemical parameters (glucose, protein, pH, specific gravity) are generally preserved with cold storage 1, 2
• Bacterial colony counts remain stable for up to 24 hours with refrigeration in specimens with high bacterial loads (≥10⁵ CFU/mL) 2
• White blood cells and red blood cells are adequately preserved within the 4-hour refrigerated window 2, 3

Important Caveats About Cold Storage

There are specific cold-induced changes that typically do not affect clinical interpretation:

• Cold storage can cause uromodulin polymer formation when urine is kept below 4°C, which can trap extracellular vesicles and some cellular elements 1, 2
• These polymers may cause cold-induced precipitation that can be reversed by warming the sample for 5 minutes at 37°C before analysis 1
• For specialized testing (RNA analysis, extracellular vesicles), some studies suggest room temperature may be preferable to cold storage, but this does not apply to routine urinalysis 1
• Crystal and cast formation artifacts may increase with prolonged cold storage 2

Clinical Bottom Line for Your Situation

Your specimen should be acceptable for testing if:

• The cold storage duration was less than 4 hours before processing 2
• The specimen was kept continuously cold (not subjected to temperature fluctuations) 3
• The laboratory processed it according to standard protocols 1, 2

The specimen should be rejected and recollected only if:

• It was refrigerated for more than 4 hours without preservatives 2
• It was kept at room temperature for more than 1 hour before refrigeration 2
• The storage time or temperature history is unknown 2

What to Communicate to Your Healthcare Provider

If you have concerns about your results, inform your provider:

• The approximate duration the specimen was kept cold before testing 1, 2
• Whether the specimen was ever at room temperature for any extended period 2
• Any visible precipitation or cloudiness that developed during cold storage 1

The laboratory should document any delay in processing in their report to alert clinicians to potential effects on cellular elements, though these effects are minimal within the 4-hour refrigerated window 2, 4