Publication:

Comparing the accuracy of nasopharyngeal COVID-19 PCR alone versus combined nasopharyngeal and oropharyngeal COVID-19 PCR tests

Background Efficient containment of the SARS-CoV-2 virus, responsible for the COVID-19 pandemic, is heavily reliant on precise diagnostic methodologies. Amidst prevalent use of nasopharyngeal (NP) and oropharyngeal (OP) swabs for detection, the superiority in sampling method effectiveness remains debated.

Methods A retrospective study within Qatar's Primary Health Care Corporation (PHCC) contrasted the accuracy of combined NP/OP PCR tests versus NP-only tests, utilizing inconclusive test rates, primarily attributed to sampling adequacy, as a crucial accuracy measure. A total of 179,694 NP/OP and NP-only samples were analyzed across two phases: pre and post-16/01/2022, the latter marking a transition predominantly to NP-only swabs and increased reliance on rapid antigen testing. With a notable disparity in sample size between methods, a 1% simple random sample was extracted for analysis. Patients aged 18 years and below were excluded in this study.

Results The dual NP and OP swab approach registered a 2% inconclusive rate pre-cut off, while a 5% inconclusive rate was observed with the NP-only technique post-cut off, presenting a statistically significant 3% differential (p<0.001). Subgroup analyses divulged a mere 1% inconclusive rate disparity between age groups and a 1% lower rate amidst symptomatic individuals, with chronic allergic rhinitis patients exhibiting a 2% elevation (p=0.086).

Conclusions Combined NP/OP swabbing produced fewer inconclusive PCR results relative to NP-only swabbing, offering a 3% improvement in conclusive diagnostics. Notably, symptomatic presentation and chronic allergic rhinitis most significantly influenced accuracy, indicating potential avenues for further diagnostic refinement research, thus bolstering our current understanding and mitigation approaches towards COVID-19.