Value of 3-D-Printed Swabs for Respiratory Sampling and Testing

Appropriate collection of respiratory samples is essential for diagnostic testing of respiratory pathogens such as, SARS-CoV-2. During the early pandemic period, there was a shortage of imports such as, nasopharyngeal (NP) swabs in Pakistan, which led to difficulties in sampling for COVID-19 tests. At the Aga Khan University, we developed a 3D-printed anterior nares nasal swab kit paired with in-house viral transport medium (VTM) to address this gap. We conducted a prospective observational study to compare sampling with 3D-printed swab kit and standard NP commercial swab and VTM kits, in 200 individuals presenting for diagnostic testing for SARS-CoV-2 between August and September 2020. The effectiveness of the standard NP and 3D swabs were assessed using RT-PCR results of tested specimens. Results were evaluated based on cut offs of ≤ CT 35 (high to medium viral loads) or, ≤ CT 37 (low viral loads). For the former, 3D swab-based testing had a sensitivity of 93%, specificity of 99%, positive predictive value (PPV) of 98.5%, and negative predictive value (NPV) of 96.2%, respectively. For the latter, sensitivity was 88%, with specificity of 99%, with PPV of 98.5%, and NPV of 93.2%.%. In conclusion, 3D swab-based sampling of anterior nares was comparable with NP sampling using standard swabs, providing a reliable and convenient local solution for respiratory sample collection. Our work highlights the value of using 3D printing for diagnostic tools for convenient and effective sampling when items are scarce. 3D printing also provides new opportunities for rapid assay development as prototypes prior to scale up.