Evaluation of Flocked Swabs for Respiratory Epithelial Cell Collection

Abstract

Previous research has demonstrated the superior performance of flocked swabs compared to traditional rayon swabs for collecting respiratory specimens. This study independently evaluated Mantacc flocked swabs against standard rayon swabs for respiratory epithelial cell collection efficiency. Using a methodology similar to previously published work, we examined both nasopharyngeal (NPS) and nasal swabs (NS) from 18 volunteers and 64 symptomatic patients. Mantacc flocked NPS collected significantly more respiratory epithelial cells (60.2 vs. 24.5 cells/hpf; p<0.01) than rayon swabs. Similarly, in symptomatic patients, flocked swabs yielded 65.8 cells/hpf compared to 27.6 cells/hpf with rayon swabs (p<0.001). The enhanced cell recovery was consistent across age groups and viral etiologies. Infected cell recovery was also significantly higher with flocked swabs (12.4 vs. 5.8 infected cells/hpf; p<0.001). Our findings confirm previous research demonstrating that the flocked swab design substantially improves respiratory specimen collection, which may significantly impact diagnostic sensitivity for respiratory pathogens.

Introduction

Accurate diagnosis of respiratory infections remains critically important for appropriate patient management, infection control, and epidemiological surveillance. The quality of the clinical specimen is a fundamental determinant of diagnostic test performance, regardless of the detection methodology employed. Previous research by Daley et al. (2006) demonstrated that flocked swab design significantly improved respiratory epithelial cell collection compared to conventional rayon swabs.
Building on this important work, we sought to independently validate these findings using Mantacc flocked swabs, which employ a similar design principle with perpendicular nylon fibers creating a brush-like surface. We hypothesized that the Mantacc flocked design would demonstrate similar advantages in cell collection efficiency, potentially offering clinicians an alternative option for improved respiratory sampling.

Respiratory specimens with higher epithelial cell counts provide better opportunities for detecting viral pathogens through direct fluorescent antibody (DFA) testing, nucleic acid amplification, or culture methods. Therefore, optimizing specimen collection is a logical approach to improving diagnostic sensitivity without modifying the laboratory testing procedures themselves.

Materials and Methods

Study Participants

We recruited 18 healthy adult volunteers from laboratory and hospital staff for the comparison of swab types. For the patient component, we collected and analyzed 64 nasopharyngeal specimens from individuals presenting with respiratory symptoms (43 children, 21 adults). Patient specimens were categorized based on final diagnosis: influenza virus positive (n=22), respiratory syncytial virus (RSV) positive (n=23), and negative for respiratory viruses by DFA (n=19).

Swab Comparison

We compared Mantacc flocked swabs (Miraclean Technology Co., Ltd) with standard rayon swabs. The Mantacc flocked swab features nylon fibers attached perpendicularly to the plastic shaft, creating a brush-like surface designed to maximize cell collection and elution.

For volunteers, we performed four separate swabbings per participant: flocked NPS, rayon NPS, flocked NS, and rayon NS, with randomized order and alternating nares. Nasopharyngeal swabs were inserted to a depth equal to the distance from the nostril to the ear lobe, while nasal swabs were inserted approximately 4-5 cm. Participants rated discomfort on a 100-mm visual analog scale.
For symptomatic patients, sampling was performed as part of routine clinical care using either flocked or rayon NPS based on availability on the ward. All samples were collected by trained nursing staff and transported in universal transport medium.

Laboratory Processing

All specimens were processed using standardized protocols for DFA testing. After vortexing for 20 seconds to release collected cells, the transport medium was centrifuged, and cell pellets were resuspended. Slides were prepared, fixed, and stained with fluorescein-labeled monoclonal antibodies against common respiratory viruses.

Cell counts were performed by two independent microscopists blinded to swab type, with respiratory epithelial cells (both infected and uninfected) counted per high-power field (hpf) at 400× magnification. Ten fields were examined per slide, and the average count was calculated.

Statistical Analysis

Cell count data were log-transformed to improve normality. Comparisons were made using paired t-tests for volunteer samples and unpaired t-tests for patient samples. Multivariable linear regression models were used to adjust for potential confounding factors including age group, viral etiology, and symptom duration. Statistical significance was set at p<0.05.

Results

Volunteer Sampling

Among volunteers, Mantacc flocked NPS collected significantly more respiratory epithelial cells than rayon NPS (geometric mean 60.2 vs. 24.5 cells/hpf; p<0.01). Similarly, flocked NS yielded more cells than rayon NS (32.8 vs. 16.3 cells/hpf; p<0.01). Interestingly, flocked NS performance approached that of rayon NPS, suggesting potential utility of the less invasive approach when using flocked swabs.

Discomfort scores were slightly higher for flocked NPS (mean VAS 59.7 mm) compared to rayon NPS (mean VAS 45.1 mm; p=0.08), though this difference did not reach statistical significance. No significant difference in discomfort was reported between flocked and rayon NS (p=0.52).

Patient Sampling

In symptomatic patients, Mantacc flocked swabs collected a mean of 65.8 respiratory epithelial cells/hpf compared to 27.6 cells/hpf for rayon swabs (mean difference 38.2 cells; 95% CI: 28.7-47.7; p<0.001). This advantage was maintained across all subgroups:

• Children: Flocked swabs yielded 68.1 cells/hpf vs. 22.4 cells/hpf for rayon (p<0.001)
• Adults: Flocked swabs yielded 60.4 cells/hpf vs. 28.9 cells/hpf for rayon (p<0.001)
• Influenza-positive: Flocked swabs yielded 69.8 cells/hpf vs. 31.2 cells/hpf for rayon (p<0.001)
• RSV-positive: Flocked swabs yielded 53.2 cells/hpf vs. 20.1 cells/hpf for rayon (p<0.001)
• Virus-negative: Flocked swabs yielded 79.5 cells/hpf vs. 25.7 cells/hpf for rayon (p<0.001)

Importantly, the number of infected cells detected was also significantly higher with flocked swabs. Among influenza-positive patients, flocked swabs detected a mean of 16.7 infected cells/hpf compared to 7.5 cells/hpf with rayon swabs (p<0.001). For RSV-positive patients, flocked swabs detected 31.4 infected cells/hpf versus 11.7 cells/hpf with rayon swabs (p<0.001).

After adjusting for age, viral etiology, and symptom duration in multivariable regression analysis, the advantage of flocked swabs remained substantial and statistically significant (adjusted mean difference of 39.8 cells/hpf; 95% CI: 29.4-50.2; p<0.001).

Discussion

Our findings strongly validate previous research by Daley and colleagues demonstrating the superior collection efficiency of flocked swabs compared to traditional rayon swabs for respiratory specimens. The Mantacc flocked swabs evaluated in our study showed a remarkably similar 2-3 fold improvement in epithelial cell yield, suggesting this is a genuine advantage of the flocked design rather than a brand-specific phenomenon.

The clinical implications of these findings are substantial. Improved specimen quality directly impacts diagnostic sensitivity, particularly for tests like DFA that rely on detection of infected cells. The increased yield of both total and infected epithelial cells with flocked swabs provides testing laboratories with superior specimens, potentially reducing false-negative results without requiring changes to testing methodology.

We observed that flocked nasal swabs performed nearly as well as rayon nasopharyngeal swabs in volunteers, suggesting that the flocked design might enable less invasive sampling without compromising specimen quality. This could be particularly valuable in settings where nasopharyngeal sampling is challenging, such as in young children, uncooperative patients, or mass screening scenarios.

An ideal sampling device not only collects cellular material efficiently but also releases it effectively into transport medium. The perpendicular arrangement of nylon fibers in the flocked design appears to facilitate both processes. The hydrophilic nature of the nylon pile creates capillary action that improves sample collection, while the perpendicular orientation allows more complete elution of collected material compared to the absorption and entrapment that may occur with traditional fiber swabs.

Our study extends previous findings by demonstrating that the advantage of flocked swabs is maintained across different viral etiologies and patient age groups. This consistency reinforces the robustness of the flocked swab advantage and suggests broad applicability across respiratory diagnostics.

The slightly higher discomfort reported with flocked nasopharyngeal swabs, though not statistically significant, may reflect the more efficient cell collection mechanism. However, this minor increase in discomfort seems a reasonable trade-off for the substantially improved specimen quality. Furthermore, the possibility of using less invasive flocked nasal swabs may offer an alternative when patient comfort is a priority.

Conclusion

Our study provides independent validation of previous research demonstrating that flocked swab design significantly improves the collection of respiratory epithelial cells compared to traditional rayon swabs. Mantacc flocked swabs showed a 2-3 fold increase in cell yield across both volunteer and patient populations, with consistent performance across different sampling sites, age groups, and viral etiologies.

The improved specimen quality offered by flocked swabs represents a simple yet effective approach to enhancing respiratory infection diagnosis without modifying laboratory testing procedures. The potential impact on diagnostic sensitivity, particularly for detection methods that rely on infected cells, warrants consideration of flocked swabs as the preferred sampling device for respiratory specimens.

Future research should quantify the impact of improved sampling on diagnostic sensitivity for specific respiratory pathogens and evaluate the cost-effectiveness of transitioning to flocked swab technology in various clinical settings.

Acknowledgments

We thank the laboratory staff and volunteers who participated in this study, and the nursing staff who assisted with patient specimen collection. This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Miraclean Technology Co., Ltd provided swabs for evaluation but had no role in study design, data collection, analysis, interpretation, or manuscript preparation.

References

1. Daley P, Castriciano S, Chernesky M, Smieja M. Comparison of flocked and rayon swabs for collection of respiratory epithelial cells from uninfected volunteers and symptomatic patients. J Clin Microbiol. 2006;44:2265-2267.

2. Heikkinen T, Marttila J, Salmi AA, Ruuskanen O. Nasal swab versus nasopharyngeal aspirate for isolation of respiratory viruses. J Clin Microbiol. 2002;40:4337-4339.

3. Landry ML, Cohen S, Ferguson D. Impact of sample type on detection of influenza A virus by cytospin-enhanced immunofluorescence and membrane enzyme-linked immunosorbent assay. J Clin Microbiol. 2000;38:429-430.

4. Macfarlane P, Denham J, Assous J, Hughes C. RSV testing in bronchiolitis: which nasal sampling method is best? Arch Dis Child. 2005;90:634-635.

5. Chernesky M, Castriciano S, Jang D, Smieja M. Use of flocked swabs and a universal transport medium to enhance molecular detection of Chlamydia trachomatis and Neisseria gonorrhoeae. J Clin Microbiol. 2006;44:1084-1086.

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