Preclinical Validation of a Novel Injection-Molded Swab for the Molecular Assay Detection of SARS-CoV-2

Abstract

During the COVID-19 public health emergency, many actions have been undertaken to help ensure that patients and health care providers have timely and continued access to high-quality medical devices to respond effectively. The development and validation of new testing supplies and equipment, including collection swabs, has helped to expand the availability and capability for various diagnostic, therapeutic, and protective medical devices in high demand during the COVID-19 emergency. Here, we report the initial validation of a new injection-molded anterior nasal swab, ClearTip™, that was experimentally validated in a laboratory setting as well as in independent clinical studies in comparison to gold standard flocked swabs. We have also developed an in vitro anterior nasal tissue model which offers a novel, efficient, and clinically relevant validation tool to replicate the clinical swabbing workflow with high fidelity, while being accessible, safe, reproducible, and time- and cost-effective. ClearTip™ displayed greater inactivated virus release in the benchtop model, confirmed by its greater ability to report positive samples in a small clinical study in comparison to flocked swabs. We also quantified the detection of biological materials, as a proxy for viral material, in multi-center pre-clinical and clinical studies which showed a statistically significant difference in one study and a reduction in performance in comparison to flocked swabs. Taken together, these results emphasize the compelling benefits of non-absorbent injection-molded anterior nasal swabs for COVID-19 detection, comparable to standard flocked swabs. Injection-molded swabs, as ClearTip™, could have the potential to support future swab shortages, due to its manufacturing advantages, while offering benefits in comparison to highly absorbent swabs in terms of comfort, limited volume collection, and potential multiple usage.

Keywords: COVID-19; SARS-CoV-2; diagnostic testing; swab; tissue model; virological testing.

Figure 1

Experimental swabs. Macro images of ClearTip™ injection-molded, Steripack, and Copan anterior nasal swabs used in these studies. Scale bar = 10 mm.

Figure 2

ClearTip^TM benchtop validation. (A) Anterior nasal tissue model comprising a cellulose sponge loaded with synthetic nasal mucus spiked with inactivated SARS-CoV-2. The cellulose sponge mimicked the nasal soft tissue during the benchtop swabbing procedure with the ClearTip^TM in comparison to flocked control swab. (B) Mass uptake during the benchtop swabbing procedure was quantified by gravimetrical analysis. Flocked control samples displayed a statistically greater mass update compared with ClearTip^TM. (C) Swab material release was collected into viral transport media, and inactivated virus was quantified using PCR following CDC guidelines. * Statistical difference against flocked control group (p < 0.05). Created with BioRender.com (Accessed on 9 January 2021).

Figure 3

ClearTip^TM Preclinical self-sampling validation. Pre-clinical self-sampling study was performed to compare performance of ClearTip^TM swab against flocked swab. In this study, numbers of total cells (A), live cells (B), and dead cells (C) were quantified, as well as DNA content (D) and RNase P expression (E). * Statistically significant differences were only reported for live cells, DNA content and RNase P (p < 0.05).

Figure 4

ClearTip^TM clinical validation for RNase P detection. Two independent clinical studies were performed to quantify the ability of the ClearTip^TM swab to pick up nasal cellular material in comparison to control flocked nasal swabs. (A) Clinical study at the CAPCaT University of Massachusetts Lowell showed a significant increase in cycle time for the detection of RNase P collected by ClearTip^TM Swabs and Steripack Nasal Swabs (p < 0.05). (B) Clinical study at Washington University St. Louis showed no statistical difference (p = 0.945) in cycle time for the detection of RNase P collected by ClearTip^TM Swabs and Copan Nasal Swabs. * Statistical difference against flocked NP control (p < 0.05).

Figure 5

ClearTip^TM concordance with control swabs. Summary of positive and negative samples detected with the ClearTip™ swab in comparison to Copan flocked swab. The statuses of participants enrolled in the study were confirmed by an EUA-approved RT-PCR COVID-19 virus test result, performed with NP flocked swabs.

Figure 6

ClearTip^TM comfort study. (A) Summary of comfort survey with ratings on a 5-point Likert scale, with 1 = very uncomfortable and 5 = very comfortable. (B) Mean paired difference in swab comfort. ClearTip™ was found to be equivalent to the flocked CLIA-approved swab with a paired t-test equivalence margin of 1 (p < 0.05).