Abstract 14884: Variation of Immune Function Assay Within the First Year After Heart Transplantation

Introduction: The ImmuKnow® immune function assay (IFA) is used in heart transplant recipients to measure lymphocyte-mediated cell immunity via CD4 cell ATP production. Values <225 ng/mL are associated with increased infection risk; however, serial changes in the first year after heart transplant are not well reported. We evaluated IFA trends for heart transplant recipients over the first year after transplantation.

Methods: This is a single-center cohort study of consecutive heart transplant recipients from 1/1/2014-8/31/2022 that had an IFA obtained within 30-days of transplant and >1 subsequent IFA within the first year after transplant. We described the relative and absolute change of mean IFA in 90-day increments through the first year after transplant, including sex specific differences. Multivariable logistic regression models tested the independent association of patient-level clinical characteristics factors with IFA values <225 ng/mL.

Results: In the study cohort, (121/315) (38%) had an IFA within 30-days prior to transplant. Most patients were white non-Hispanic (46%) and male (74%). IFA values decreased from the pre-transplant baseline with mean absolute changes of 92 ng/mL (-24%), 120 ng/mL (-31%), 121 ng/mL (-32%), and 114 ng/mL (-28%) every 90 days after transplant, respectively (panel B). The highest prevalence of an IFA value <225 ng/mL occurred 90-180 days post-transplant in 55/103 (53%) patients. Female patients had a greater absolute and relative decrease in IFA values from baseline and each 90-day period (panel C). In exploratory analysis, at the time of transplant age >60 was associated with a lower risk of IFA values <225 during days 90-180 post-transplant (OR 0.24, p=0.02). A creatinine >1.4 mg/dL was associated with IFA values <225 during 90-180 (OR 3.15, p=0.02) and 180-270 (OR 3.44, p=0.03) days.

Conclusion: Heart transplant recipients experienced ~25% reduction in IFA value from baseline in the first-year post-heart transplant.