Risk factors and immunological characteristics of SARS-CoV-2 RNA re-positivity in convalescent COVID-19 Patients: A retrospective study

Purpose: To investigate the incidence, clinical features, and risk factors for SARS-CoV-2 nucleic acid re-positivity in recovered COVID-19 patients. Methods: We enrolled 441 convalescent COVID-19 patients from the rehabilitation ward of the Fifth Hospital of Shijiazhuang between January and April 2021. Based on nucleic acid test results, patients were categorized into repositive (n = 69) and non-repositive (n = 372) groups. Demographic, clinical, laboratory, and imaging data were compared between groups. Logistic regression was used to identify factors associated with re-positivity. Results: The overall re-positivity rate was 15.65%. Compared with the non-repositive group, the repositive group presented with a significantly higher proportion of moderate disease severity (72.46% vs. 50.54%) and a lower proportion of patients under 14 years old (7.25% vs. 23.66%). Additionally, multi-lobar involvement ([≥] 3 lobes) during the acute phase was more common in the repositive group (43.48% vs. 26.61%), with all differences being statistically significant (P < 0.001). Laboratory analysis revealed that repositive patients had significantly lower lymphocyte and eosinophil counts, as well as reduced albumin (ALB), aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio, and albumin/globulin (A/G) ratio. Furthermore, circulating CD3+, CD4+, and CD8+ T-cell counts were markedly decreased. In contrast, the neutrophil-to-lymphocyte ratio (NLR), immunoglobulin M (IgM), immunoglobulin A (IgA), and neutralizing antibody (NAb) levels were significantly elevated in re-positive patients (all P < 0.05). Multivariate logistic regression analysis identified the CD8+ as independent risk factors for re-positivity. Conclusion: In convalescent patients, SARS-CoV-2 RNA re-positivity correlates with distinct clinical and immunological characteristics. The CD8+ T-cell level is an independent predictor, highlighting that dysregulated immune and inflammatory responses contribute to delayed viral clearance.