What Are The Better Sampling Swabs for COVID-19 Testing?

With the COVID-19 pandemic, accurate testing using respiratory samples has become critical. However, which sample type performs the best? Various studies have compared different respiratory specimens for detecting SARS-CoV-2. This article summarizes the key findings.

What About Different Swab Types for Sample Collection?

Multiple studies compared swabs like nylon, polyester, cotton, and dacron for collecting COVID-19 samples. A study testing 6 swab types found all gave similar SARS-CoV-2 RNA yields. However, virus recovery efficiency varied due to differences in absorbance and elution volumes. Overall, swab materials did not significantly impact detection when placed in a proper transport medium.

How Do Nasopharyngeal and Oropharyngeal Swabs Compare?

Several studies found nasopharyngeal (NP) swabs were more sensitive for COVID-19 detection than oropharyngeal (OP) swabs. However, NP swabs had higher collection risks, requiring close provider contact and causing discomfort. OP swabs may be easier to collect but have higher false negatives. For children, NP swabs may be more challenging.

What About Saliva Specimens Compared to Swabs?

Multiple studies assessed saliva, finding it was slightly less sensitive than NP swabs but with easier and safer collection. Self-collected saliva could be a feasible alternative, especially for population screening. However, optimal collection protocols and more data are needed to validate saliva as a standard.

Are There Advantages of Sputum for Testing?

Sputum samples had higher viral loads than upper respiratory samples in some studies. Sputum may be beneficial for symptomatic patients with productive coughs and initial negative NP swabs. However, sputum collection carries higher risk and is not possible for all patients.

Do Swab Materials Impact Patient Comfort?

Studies in adults found dacron swabs caused less discomfort than nylon during nasal sampling. But for children, nylon swabs had better performance and comfort. Despite differences in patient experience, swab materials gave comparable test results. Patient factors should determine appropriate swab selection.

How Do Transport Media Compare for Sample Storage?

Transport media like viral transport media (VTM), PBS, and ethanol could effectively maintain SARS-CoV-2 RNA integrity for molecular testing. However, normal saline was inadequate for viral preservation. Proper media can stabilize specimens until laboratory analysis.

Can Direct RT-PCR Without RNA Extraction Be Used?

Some methods successfully detected SARS-CoV-2 using direct RT-PCR on untreated samples, saving time and cost. However, optimal protocols, transport media, and PCR kits are needed to match standard extraction-based testing. Direct RT-PCR warrants further research for feasible implementation.

In summary, all sample types and test methods have trade-offs. Understanding performance comparisons can inform selective use of specimens and procedures to improve COVID-19 diagnosis. Ongoing studies are still needed to standardize and streamline testing workflows.

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References

1. 1. Ahmadzadeh M, Vahidi H, Mahboubi A, Hajifathaliha F, Nematollahi L, Mohit E. Different Respiratory Samples for COVID-19 Detection by Standard and Direct Quantitative RT-PCR: A Literature Review. Iran J Pharm Res. 2021 Summer;20(3):285-299. doi: 10.22037/ijpr.2021.115458.15383. PMID: 34903989; PMCID: PMC8653661.
2. 2. Bidkar V, Selvaraj K, Mishra M, Shete V, Sajjanar A. A comparison of swab types on sample adequacy, suspects comfort and provider preference in COVID-19. Am J Otolaryngol. 2021 Mar-Apr;42(2):102872. doi: 10.1016/j.amjoto.2020.102872. Epub 2020 Dec 29. PMID: 33418177; PMCID: PMC7831439.
3. 3. Garnett L, Bello A, Tran KN, Audet J, Leung A, Schiffman Z, Griffin BD, Tailor N, Kobasa D, Strong JE. Comparison analysis of different swabs and transport mediums suitable for SARS-CoV-2 testing following shortages. J Virol Methods. 2020 Nov;285:113947. doi: 10.1016/j.jviromet.2020.113947. Epub 2020 Aug 8. PMID: 32781008; PMCID: PMC7414358.