2.1. Study design
The study was part of our previous retrospective study of Covid-19
patients in Yogyakarta and Central Java provinces,
Indonesia.36 Briefly, the study was conducted from May
2021 to February 2022. We collected nasopharyngeal swabs of outpatient
or hospitalized patients with Covid-19 for RT-PCR testing in the
Laboratory of Covid-19, Faculty of Medicine, Public Health and Nursing,
Universitas Gadjah Mada, Yogyakarta. During the study period, 352
confirmed Covid-19 patients (based on RT-PCR), consisting of 164 males
and 188 females, were recruited.