Baseline characteristics of the patients
Upon hospital admission, patients’ baseline characteristics were gathered, including sex, age, clinical classification(i.e., severity of symptoms), underlying health conditions, risk factors of developing severe illness, and immunization record. The number of days from the onset of symptoms or a positive RT-PCR test to hospitalization and to initiation of treatment were calculated. Within 2 days of being admitted to the hospital, respiratory samples were obtained from the upper respiratory tract of patients using a nasopharyngeal swab. The samples underwent testing using a real-time fluorescence quantitative RT-PCR method to detect the presence of the SARS-CoV-2 virus. The targets for the RT-PCR assay were open reading frame 1ab (ORF), nucleocapsid protein gene (N gene) and envelope protein gene (E gene). All the targets were recorded with the cycle threshold (Ct) value, which represents the number of cycles required to amplify the viral nucleic acid to a detectable level. A Ct value below 35 for ORF, N gene or E gene was used to define a positive sample of SARS-CoV-2[17].
Intervention and control
Every patient was provided with standard care, which involved resting in bed, monitoring vital signs, measuring oxygen saturation, conducting routine blood chemistry and urine analysis, examining biochemical indicators such as liver and myocardial enzymes and renal function, assessing coagulation parameters, analyzing arterial blood gas, conducting chest imaging and cytokine detection, and administering oxygen therapy if necessary. Individuals in the intervention cohort were administered nirmatrelvir at a dosage of 300 mg alongside ritonavir at a dosage of 100 mg, twice a day, for a duration of 5 days. Alternatively, if patients’ eGFR ranged from 30-59 mL/min per 1.73 m², the dosage of nirmatrelvir was reduced to 150 mg while ritonavir remained at 100 mg. Patients in the control group only obtained standard care and were not administered nirmatrelvir-ritonavir. Patients in both groups did not receive any other medications specifically for COVID-19, such as remdesivir or monoclonal antibodies.