Indications for SARS-CoV-2 nucleic acid amplification test for areas with low endemicity

Introduction: The optimal indication for the nucleic acid amplification test (NAAT) in areas with low endemicity for coronavirus disease 2019 (COVID-19) is unclear. This study aimed to identify patients who should undergo the NAAT for COVID-19 diagnosis.

Methods: We retrospectively analyzed the clinical data of patients with suspected COVID-19 who underwent NAAT between October 5, 2020, and May 31, 2021 in our institution.

Results: A total of 1238 patients were enrolled and NAAT positive results were observed in 40 patients (3.2%). The NAAT positivity rate was 34.3% (23/67) in patients with a history of close contact and 1.5% (17/1171) in patients without a history of close contact. Olfactory/gustatory dysfunction and a history of stay in other prefectures were independent risk factors of COVID-19 in patients without a history of close contact. On the other hand, the NAAT positivity rate was only 0.7% (8/1073) in patients without olfactory/gustatory dysfunction and a history of stay in other prefectures. Among them, the group without respiratory symptoms/sign had only one NAAT-positive case (0.1%: 1/1073).

Conclusions: This study revealed that a history of close contact, olfactory/gustatory dysfunction, and a history of stay in other prefectures are key eligibility criteria for NAAT in areas with relatively few patients with COVID-19. On the other hand, NAAT may not be necessary in cases without all of these factors and respiratory symptoms/sign.