A Comparative Study of the Diagnostic Value of Once and Twice Nasopharyngeal, Oropharyngeal, and Anal Swabs, and Saliva Specimens in COVID-19 Infection

Since the emergence of COVID-19 and the pandemic declaration, this disease has become the top priority for global healthcare systems. The standard diagnostic tool for COVID-19 involves conducting imaging studies alongside real-time polymerase chain reaction (RT-PCR) tests on nasopharyngeal or oropharyngeal samples.

Given the potential extrapulmonary involvement of COVID-19, our objective was to evaluate the diagnostic effectiveness of double pharyngeal sampling, as well as the use of saliva and anal swabs.

This cross-sectional study involved 102 pediatric patients suspected of having COVID-19. After the routine nasopharyngeal sampling, additional samples were collected from the nasopharynx, saliva, and anal canal. These samples were subjected to RT-PCR testing using Taq Man’s probe-based technology. The statistical analysis included sensitivity, specificity, positive and negative predictive values, and Kappa agreement measurement.

In this study, with a COVID-19 prevalence of 92.2%, we compared the diagnostic efficacy of different methods. When having at least one positive sample was considered the gold standard, double nasopharyngeal sampling exhibited the highest sensitivity, followed by RT-PCR of saliva and anal swabs (94.9%, 92.9%, and 91.9%, respectively). When double sampling was considered the gold standard for diagnosis, saliva RT-PCR showed the highest sensitivity and negative predictive value (93.6% and 40.0%, respectively). However, there was no significant difference in the specificity and positive predictive value between anal swabs and saliva RT-PCR. However, when anal swabs and saliva were compared with only one nasopharyngeal sample, anal swabs performed slightly better than saliva.

While the combination of double sampling from the nasopharynx and oropharynx, along with anal swabs and saliva, proved effective for diagnosing COVID-19, routine use of these methods may not be cost-effective. However, during periods of epidemic control, when comprehensive case identification is crucial, these methods may warrant consideration for more extensive investigations.