Comparative Study of Nasopharyngeal Swab, Oropharyngeal Swab and Oral Saliva for the Diagnosis of COVID-19

Abstract

Introduction: The world has been affected by COVID-19 in recent years. There are various sampling sites which have given different yields. Methods: In cross sectional, prospective and descriptive study, 3 sampling sites namely oropharyngeal (OP), nasopharyngeal (NP) and oral saliva (OS) were compared as regards to COVID-19 yield. Results: A total of 939 samples were collected from 313 patients. Among these patients, 16 had samples positive from all three sites. There were 6 patients who had both nasopharyngeal and oropharyngeal swabs which showed positive results for COVID-19, while there were 4 patients each in whom only either oropharyngeal or nasopharyngeal swabs were positive. One patient had positive sample for oropharyngeal and oral saliva, while there was no patient in whom only saliva was positive. Thus a total of 27 patients had atleast one sample which was positive. Conclusion: Both nasopharyngeal and oropharyngeal samples are important and also both samples should be taken from all patients in order to reduce false negative results. Oral saliva as the only sampling site cannot be relied on owing to its low yields.