Clinical validation of 3D-printed swabs in adults and children for SARS-CoV-2 detection

Abstract

Throughout the entire coronavirus disease 19 (COVID-19) pandemic, there were disruptions in the supply chain of test materials around the world, primarily in poor- and middle-income countries. The use of 3D prints is an alternative to address swab supply shortages. In this study, the feasibility of the clinical use of 3D-printed swabs for oropharyngeal and nasopharyngeal sampling for the detection of SARS-CoV-2 infection was evaluated. For that purpose, paired samples with the 3D printed and the control swabs were taken from 42 adult patients and 10 pediatric patients, and the results obtained in the detection of SARS-CoV-2 by reverse transcription and quantitative polymerase chain reaction (RT-qPCR) were compared. Additionally, in those cases where the result was positive for SARS-CoV-2, the viral load was calculated by means of a mathematical algorithm proposed by us. For both adults and children, satisfactory results were obtained in the detection of SARS-CoV-2 by RT-qPCR; no significant differences were found in the quantification cycle values between the 3D-printed swab samples and the control samples. Furthermore, we corroborated that the 3D-printed swabs caused less discomfort and pain at the time of sampling. In conclusion, this study shows the feasibility of routinely using 3D-printed swabs for both adults and children. In this way, it is possible to maintain local and cheaper consumption along with fewer distribution difficulties.

Keywords: 3D-printed swabs; COVID-19; SARS-CoV-2; clinical validation; polylactic acid; thermoplastic elastomers.

Figure 1.

Pediatric 3D-printed and control swabs used in this study. (A) Pictures of the complete TPE 3D-printed swab and its collection head. The swab has a breakpoint (marked with thick arrow) to improve the handling. (B) Pictures of the complete control swab (with no breakpoint) and its collection head. Dimensions are described in the pictures.

Figure 2.

Comparative box plots between Cq values of RT-qPCR experiments. (A) IC gene (internal control) Cq values of samples taken with the control swabs and the 3D-printed swabs. (B) Cq values of the viral genes (E, N, and RdRp) of samples taken with the control swabs and the 3D-printed swabs. (C) IC gene Cq values of pediatric samples taken with the control swabs (NS and OP together), the 3D-printed NS swab, and the 3D-printed OP swab. P-values are shown for each comparison. The middle line of each box represents the median of the Cq values.

Figure 3.

Relative viral load in positive samples detected with 3D-printed and control swabs. The relative viral load of the samples obtained for each patient with the 3D-printed swab (orange triangles) and the control swab (blue circles) are represented in each horizontal line. Values < −1 = low viral load (L), values between −1 and 1 = medium viral load (M), values > 1 = high viral load (H). Vertical dotted lines indicate the cut-offs.