Can Nasal Swabs Contain Tissue Bits and Other Sediments?
Yes, nasal swabs routinely contain epithelial cells, tissue debris, and other cellular material from the nasal mucosa, and the presence of these elements actually indicates adequate sample collection technique.
What Nasal Swabs Normally Contain
Cellular Components
- Ciliated columnar epithelial cells (CCEs) are the primary tissue component expected in properly collected nasal swabs, as they are prevalent throughout the nasopharynx 1
- The presence of epithelial cells in nasal swabs is normal and expected, though cells from the anterior nares or nasal vestibule may represent contamination that reduces diagnostic value 2
- Samples without identifiable ciliated columnar epithelial cells have a greater likelihood of inadequate collection technique 1
Quality Indicators
- Approximately 20% of samples negative for respiratory pathogens by PCR had no ciliated columnar epithelial cells, while only 7% of positive samples lacked these cells, suggesting that tissue elements correlate with adequate sampling 1
- Microscopic examination of viral transport media from nasopharyngeal swabs reveals morphologically distinct ciliated columnar epithelial cells that can be counted as a quality assurance measure 1
Clinical Significance of Sample Contents
For Diagnostic Purposes
- Nasal swabs gather both extracellular material and human respiratory epithelial cells, and when used with RT-PCR, have reliable sensitivity for detection of viral infection 1
- The presence of tissue elements does not interfere with molecular testing and may actually indicate proper collection depth and technique 1
For Microbiological Analysis
- Tissue or tissue scrapings are actually preferred specimens over simple swabs for many upper respiratory infections, and should be transported in sterile containers under conditions that keep the specimen moist 3
- For microbiology analysis, it is always best to submit the actual specimen (including tissue), not just a swab of the specimen 3
Common Pitfalls
Contamination vs. Adequate Sampling
- While epithelial cells from the anterior nares or nasal vestibule suggest contamination, cells from deeper structures indicate proper technique 2
- The key distinction is the source: anterior contamination reduces diagnostic value, while posterior nasopharyngeal cells confirm adequate collection 2
Collection Technique Matters
- Vigorously and sufficiently rubbed nasal swabs (10 rubs vs. 5 rubs) provide significantly different viral concentrations, with more aggressive sampling yielding lower Ct values (higher viral loads) 4
- Proper nasopharyngeal swab technique should reach the posterior nasopharynx to collect ciliated columnar epithelial cells rather than just superficial debris 5, 1