Clinical Evaluation of In-House-Produced 3D-Printed Nasopharyngeal Swabs for COVID-19 Testing

Abstract

3D-printed alternatives to standard flocked swabs were rapidly developed to provide a response to the unprecedented and sudden need for an exponentially growing amount of diagnostic tools to fight the COVID-19 pandemic. In light of the anticipated shortage, a hospital-based 3D-printing platform was implemented in our institution for the production of swabs for nasopharyngeal and oropharyngeal sampling based on the freely available, open-source design provided to the community by University of South Florida's Health Radiology and Northwell Health System teams as a replacement for locally used commercial swabs. Validation of our 3D-printed swabs was performed with a head-to-head diagnostic accuracy study of the 3D-printed "Northwell model" with the cobas PCR Media^® swab sample kit. We observed an excellent concordance (total agreement 96.8%, Kappa 0.936) in results obtained with the 3D-printed and flocked swabs, indicating that the in-house 3D-printed swab could be used reliably in the context of a shortage of flocked swabs. To our knowledge, this is the first study to report on autonomous hospital-based production and clinical validation of 3D-printed swabs.

Keywords: 3D-printed nasopharyngeal swabs; COVID-19; PCR; SARS-CoV-2; diagnosis.

Figure 1

In-house 3D-printed swab model. Design of the Northwell 3D swab model with the addition of a breakout point (A) used to 3D-print swab in our hospital (B,C). Swabs were individually packed in autoclavable and vacuum-sealed pouches (D) for sterilization. (E) Flexibility was mechanically tested using semicircular canals (radius of 15, 25, and 35 mm).

Figure 2

Validation of 3D-printed swab sterilization. Swab heads inoculated with G. stearothermophilus spore suspension before sterilization cultured in soy broth culture media. Bacteria growth was assessed by measuring the optical density (O.D.) at 600 nm. Culture media alone was used as negative control.

Figure 3

Cycle threshold (Ct) values of reverse-transcriptase polymerase chain reaction (RT-PCR) for the ORF1 and E genes. Participants were swabbed in the same nostril with a flocked and a 3D-printed swab, successively. RT-PCR was performed to measure the Ct values of ORF1 (A) and E (B) viral genes for each swab. An internal control (Ctrl) was also included (C). Statistical analyses are detailed in Table 1.