[Related factors of viral nucleic acid change in critically ill patients with SARS-CoV-2 infection after treatment with Nirmatrelvir/Ritonavir: a single center retrospective cohort study].

Objective: To describe negative conversion and rebound of patients with severe and critical acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection after treatment with Nirmatrelvir/Ritonavir, and to analyze related factors associating with failure of SARS-CoV-2 negative conversion and relapse and prognosis.
Methods: A single center retrospective cohort study was conducted. Patients aged ≥ 16 years old who were diagnosed with severe or critical SARS-CoV-2 infection and took Nirmatrelvir/Ritonavir for 5 days in Peking University First Hospital from December 7, 2022 to January 27, 2023, were included. General characteristics and clinical data were collected from electronic medical record system. The Kaplan-Meier curve of SARS-CoV-2 negative conversion was drawn. Factors with P < 0.10 were incorporated into multivariate Logistic regression model to analyze the relationship between the factors and persistent nucleic acid positive and rebound.
Results: A total of 31 severe and 37 critical SARS-CoV-2 infection patients were included. The median duration from initiation of Nirmatrelvir/Ritonavir to negative conversion of SARS-CoV-2 for both was 6.0 days, and the negative conversion rate on day 15 was 93.5% and 86.5%, respectively. SARS-CoV-2 rebound was observed in 7 patients (11.3%), among whom were 1 severe patient and 6 critical patients. The above 7 patients with SARS-CoV-2 rebound and 6 patients with failure of SARS-CoV-2 negative conversion were compared with 55 patients with persistent negative conversion. Factors with P < 0.10, including the lowest lymphocyte count (LYM), the highest D-dimer, the highest procalcitonin (PCT), the lowest Ct value, cardiovascular diseases other than hypertension and coronary heart disease, were incorporated into multivariate Logistic regression analysis. The decreased LYM [odds ratio (OR) = 0.146, 95% confidence interval (95%CI) was 0.031-0.689, P = 0.015] and the increased PCT (OR = 2.008, 95%CI was 1.042-3.868, P = 0.037) were revealed to be independent risk factors of the failure of SARS-CoV-2 negative conversion or rebound. The proportion of mechanical ventilation and invasive ventilation were significantly higher in patients with persistent SARS-CoV-2 infection or rebound than those in patients with SARS-CoV-2 negative conversion (84.6% vs. 38.2%, 69.2% vs. 25.5%, both P < 0.01), but no significant difference in mechanical ventilation and invasive ventilation duration was observed. Compared with the patients with SARS-CoV-2 negative conversion, more patients with persistent SARS-CoV-2 infection or rebound were admitted to intensive care unit (ICU, 76.9% vs. 50.9%), and length of ICU stay in patients with persistent SARS-CoV-2 infection or rebound tended to be longer [days: 13.0 (10.3, 24.3) vs. 11.0 (5.3, 23.0), P > 0.05].
Conclusions: The decreased LYM and increased PCT are independent risk factors for the failure of SARS-CoV-2 negative conversion or rebound in patients with severe and critical SARS-CoV-2 infection. Attention should be paid to these patients for their poor prognosis.