Low-Cost Polyester-Tipped Three-Dimensionally Printed Nasopharyngeal Swab for the Detection of Severe Acute Respiratory Syndrome-Related Coronavirus 2 (SARS-CoV-2)

Abstract

Case identification, isolation, and contact tracing are fundamental strategies used to control the spread of coronavirus disease 2019 (COVID-19). This has led to widespread testing that interrupted the supply chain for testing materials around the world. A prospective study was conducted to compare inexpensive and easily sourced 3-dimensionally (3D)-printed polylactic acid and polyester nasopharyngeal swabs to commercially manufactured swabs for the detection of severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2). During the study period, 287 laboratory-confirmed hospitalized COVID-19 patients, at multiple stages of their illness, were enrolled. The median age for the study population was 47.6 years (interquartile range [IQR], 34.4 to 56.6 years), and two-thirds (67.6%) of the subjects were male. The median duration of hospitalization, at the time of sampling, was 13 days (IQR, 10 to 16 days). Overall concordance between the prototype and control swabs was 80.8% (Cohen's kappa coefficient, 0.61). Most discrepant results were due to prototype-positive control-negative results. When considering all positive results to be true positives, the prototype swab had a higher sensitivity (90.6% versus 80.8%; 95% confidence interval [CI], 85.7% to 94.0% and 74.7% to 85.7%, respectively; P < 0.015). The cost to produce the prototype swab was estimated to be $0.05 per swab. Polylactic acid 3D-printed polyester-tipped swabs were shown to be effective for nasopharyngeal sample collection. We believe that this design can easily be adopted in countries where commercial swabs are not readily available and can play a vital role in public health efforts for disease control in low-income countries.

Keywords: COVID-19; nasopharyngeal; swab.

FIG 1

Categorical concordance against control swabs.

FIG 2

Detailed categorical concordance of prototype swab against control swab (A), flocked swab (B), and viscose swab (C).

FIG 3

Distribution of cycle threshold (C_T) values of specimens collected using the prototype and control swab.

FIG 4

Cycle threshold (C_T) values from nasopharyngeal samples collected using the prototype swab relative to those collected using the control swab. (A) Using values related to the RNA-dependent RNA polymerase (RdRP) gene (n = 36). (B) Using values related to the E gene (n = 57). Please note that threshold values for negative results were not included in the scatterplot. Only C_T values that were available from the lab and concordant are represented in the figures.