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Evaluation of filter paper to transport oro/nasopharyngeal samples to detect SARS-CoV-2 by RT-qPCR
Maiara Dos Santos Carneiro1, Fabiana Caroline Zempulski Volpato2, Priscila Lamb Wink3
1LABRESIS - Laboratório de Pesquisa em Resistência Bacteriana, Hospital de Clínicas de Porto Alegre, Porto Alegre, Rio Grande do Sul, Brazil; Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
Purpose:
To evaluate filter paper as a means to transport oro/nasopharyngeal samples from laboratories with few resources for SARS-CoV-2 detection by RT-qPCR in a central laboratory that usually performs this technique as routine.
Methods:
A total of 40 specimens were evaluated in parallel by RT-qPCR carried out after RNA extraction using two different protocols: direct RNA extraction (Protocol A - reference method) and RNA extraction after impregnation in filter paper (Protocol B).
Results:
The RT-qPCR for SARS-CoV-2 using Protocol B presented 97.22% (35/36) of agreement for SARS-CoV-2-positive samples when compared to the reference method (Protocol A), even for specimens with low viral load (increased Ct values). Noteworthy, three clinical specimens which were categorized as inconclusive by Protocol A presented amplification of both N1 and N2 targets using Protocol B, presenting positive results for SARS-CoV-2.
Conclusion:
The use of filter paper to transport oro/nasopharyngeal clinical samples presented very satisfactory results to detect SARS-CoV-2 by RT-qPCR. In addition, it proved to be a feasible and sensitive approach, being able to generate the detection of SARS-CoV-2 even at low concentrations, without presenting false-negative results.
