Absolute lymphocyte count as marker of cytomegalovirus and allograft rejection: Is there a "Safe Corridor" after kidney transplantation?

The contrasting outcomes of lymphocyte manipulation after solid organ transplantation are allograft rejection and infections, commonly with cytomegalovirus (CMV). Peripheral blood absolute lymphocyte count (ALC) may serve as a predictive marker for these outcomes. Using a retrospective review of clinical and laboratory dataset, we aimed to determine whether a range of ALC (termed "safe ALC corridor") exists where CMV infection and rejection outcomes are minimal in a cohort of 381 kidney transplant recipients. In an extended Cox model using a time-dependent covariate for peripheral blood ALC, a value below the cut-off of 610 cells/uL was associated with the development of CMV infection both in the overall cohort (Hazard Ratio [HR] 2.25 (95% confidence internal [CI] 1.02-4.96;P = .043) and the subgroup of high-risk CMV D+/R- mismatch patients (HR 2.91 [95% CI 1.09-7.77];P = .033). In contrast, a time-dependent Cox analysis did not show any significant association between ALC and rejection (per IQR decrease, HR 1.2 [95% CI: 0.76-1.9];P = .434). Accordingly, a "safe ALC corridor" could not be defined. In conclusion, a low peripheral blood ALC (ie, threshold of 610 cells/uL) can be used to stratify the risk of CMV disease after kidney transplantation.