How long can a stool sample for faecal calprotectin remain viable for analysis?

Stool Sample Viability for Faecal Calprotectin Testing

Stool samples for faecal calprotectin should be stored at room temperature for no longer than 3 days before analysis. 1

Storage Guidelines and Timing

The British Society of Gastroenterology provides clear guidance on sample handling to ensure accurate calprotectin measurement:

• Maximum room temperature storage: 3 days before the sample must be analyzed to prevent degradation of calprotectin 1
• Optimal processing: within 24 hours when samples are stored below 4°C to prevent further metabolic activity or disruption of metabolites 2
• Freezing is acceptable for extended storage once the sample has been extracted, with stability demonstrated for up to 2.5 months when frozen 3

Sample Collection Best Practices

To minimize variability and ensure reliable results:

• Collect the first morning stool as this reduces day-to-day variability in calprotectin concentrations and provides the most reliable baseline for assessment 1, 4
• A single specimen is sufficient for initial testing—multiple samples from the same bowel movement are not required 5
• Within a single bowel movement, there is 8-23% sample variability depending on which portion of stool is sampled, but the first morning sample with a cutoff of 250 μg/g provides the most reliable indication of disease activity 4

Critical Storage Pitfalls to Avoid

• Never subject samples to freeze-thaw cycles as this compromises calprotectin stability and is not recommended for routine testing 1
• Do not delay processing beyond 3 days at room temperature as this risks degradation and inaccurate results 1
• If immediate processing is not possible, refrigerate samples below 4°C and process within 24 hours for optimal accuracy 2

Extraction and Processing Considerations

Once extracted from stool:

• Extracted samples remain stable when frozen for at least 2.5 months, allowing for batch processing or repeat analysis if needed 3
• Longer incubation time in extraction buffer (1 hour versus 10 minutes) yields significantly higher calprotectin recovery, which laboratories should standardize 6
• The extraction method and stool consistency can significantly impact results, with some extraction devices (Calex® Cap) producing 33% higher values compared to standard weighing methods 6