Assoc Prof. Thammasat University Hospital Bangkok, THA
Disclosure(s):
Sunicha No Jiraboonsri, MD,: No relevant relationships to disclose.
Introduction: Nasopharyngeal swab RT-PCR is the gold-standard in the diagnosis of COVID-19. For patients with a tracheostomy, whose altered airway essentially bypasses the nasopharynx, the yield of samples from this site in this patient population is not clearly understood. Understanding the discordance between the results from the nasopharynx and via tracheostomy for these patients is important.
Methods: This study is a prospective cross-sectional study. The nasopharyngeal swab and tracheal secretion samples were collected from 100 patients with a tracheostomy who underwent RT-PCR at Thammasat University Hospital. The participants were aged between 1 and 90 years old, not previously diagnosed with COVID-19 prior to the test nor having oxygen desaturation. The detection result, and Ct value from each site was analyzed by McNemar’s test with a 95% confidence interval.
Results: Four participants had positive results. Two of the four had discordant results. One patient tested positive only for the nasopharyngeal swab while the other tested positive only from the tracheal secretion sample. Among the discordant and concordant groups, no statistically significant difference has been found (p = 1). The average Ct ratio (ORF1Ab/N gene) of nasopharyngeal swab and tracheal secretions were 31.67/30.76 and 22.24/24.22 respectively.
Conclusions: This study showed the discordance of COVID-19 RT-PCR screening result for samples from a nasopharyngeal swab and tracheal secretions in patients with a pre-existing tracheostomy. Multiple site sampling from both the upper and lower respiratory tract is suggested in patients with a pre-existing tracheostomy.
