Persistent or Exacerbated Lymphopenia Predicts Mortality in Kidney Transplant Recipients Hospitalized with COVID-19

Lymphopenia in KTRs with COVID-19

Abstract

Objective: Kidney transplant recipients are at increased risk for severe coronavirus disease-2019 (COVID-19) because of chronic immunosuppressive therapy and impaired cellular immunity. Lymphopenia is a well-established predictor of adverse outcomes in the general population; however, the prognostic significance of persistent lymphopenia during hospitalization in kidney transplant recipients remains poorly defined. This study aimed to evaluate the association between persistent or exacerbated lymphopenia and clinical outcomes, including mortality and renal function, in hospitalized kidney transplant recipients with COVID-19.
Methods: We conducted a retrospective cohort study including adult kidney transplant recipients hospitalized with laboratory-confirmed COVID-19 at a tertiary referral center between March 2020 and January 2022. Patients were classified based on the presence or absence of persistent or exacerbated lymphopenia during hospitalization. Demographic characteristics, comorbidities, laboratory findings, treatments, and clinical outcomes were compared between groups. The primary outcome was in-hospital mortality. Secondary outcomes included intensive care unit (ICU) admission, requirement for respiratory support, requirement for invasive mechanical ventilation, length of hospital stay, requirement for hemodialysis, and renal function at 90 days after discharge. Independent predictors of mortality were identified using multivariable logistic regression analysis.
Results: A total of 181 kidney transplant recipients were included, 63% of whom developed persistent or exacerbated lymphopenia. Patients with persistent or exacerbated lymphopenia experienced significantly higher rates of ICU admission, respiratory support, invasive mechanical ventilation, prolonged hospitalization, and in-hospital mortality compared with other patients (all p < 0.05). They also had significantly higher levels of inflammatory markers, including ferritin and C-reactive protein. In multivariable analysis, persistent/exacerbated lymphopenia remained independently associated with in-hospital mortality after adjustment for age, inflammatory markers, and hemodialysis requirement [adjusted odds ratio 14.16 (95% confidence interval: 3.6-55.7), p < 0.001]. However, persistent lymphopenia was not associated with loss of renal function at 90 days.
Conclusion: Persistent or exacerbated lymphopenia during hospitalization is a strong independent predictor of in-hospital mortality among kidney transplant recipients with COVID-19 and is associated with greater disease severity and increased resource utilization. In contrast, it does not appear to predict 90-day renal function decline. Serial assessment of lymphocyte counts may provide a simple, inexpensive, and readily available tool for early risk stratification in hospitalized kidney transplant recipients with COVID-19.