Association between lymphopenia at one month post-transplant and infectious outcomes or death in heart transplant recipients.

BACKGROUND Cell-mediated immunity is a specific target of several medications used to prevent or treat rejection in orthotopic heart transplantation. Low absolute lymphocyte count (ALC) has potential to be a useful and accessible clinical indicator of overall infection risk. Though some studies have demonstrated this association in other transplant populations, it has not been assessed in heart transplant recipients. METHODS A single-center retrospective cohort study examined adult heart transplant recipients transplanted between 2000 and 2018. The exposure of interest was ALC less than 0.75 x10 3cells/µL at one month post-transplant and the primary endpoint was a composite outcome of infection (including cytomegalovirus [CMV], herpes simplex I/II or varicella zoster virus [HSV/VZV], blood stream infection [BSI], invasive fungal infection [IFI]) or death occurring after one month and before one year post-transplant. A multivariable Cox proportional hazards model was created to control for confounders identified using clinical judgment and statistical criteria. RESULTS Of 375 subjects analyzed, 101 (27%) developed the composite outcome (61 CMV, 3 HSV/VZV, 19 BSI, 10 IFI, 8 deaths). Lymphopenia (ALC<0.75 x10 3cells/µL) at one month was associated with a greater than two fold higher rate of the composite outcome (hazard ratio 2.26, 95% confidence interval 1.47-3.46, p-value <0.001) compared to patients without lymphopenia at one month. After adjustment for confounding variables, the presence of lymphopenia remained statistically significantly associated with the composite outcome (HR 1.72 95% CI 1.08-2.75, p=0.02). Conclusion: ALC measured at one month post-heart transplant is associated with an increased risk of infectious outcomes or death in the ensuing 11months. This is a simple, accessible laboratory measure.