Single time point immune function assay (ImmuKnow) testing does not aid in the prediction of future opportunistic infections or acute rejection

Abstract

Background and objectives: Current assays and tests that are used to determine the degree of immunosuppression in renal transplant recipients are suboptimal. The ImmuKnow assay (Cylex), a measure of intracellular CD4+ T cell ATP release proposed as a means to quantify cell-mediated immunity in transplant recipients, could be considered as a potential tool to identify patients at risk for opportunistic infections (OI) or acute rejection (AR).

Design, setting, participants, & measurements: We retrospectively analyzed 1330 ImmuKnow assay values in 583 renal transplant recipients at a single center from 2004 to 2009 and correlated these values with episodes of OI and AR in the subsequent 90 days. Assay values were compared with a control population matched for age, gender, and time post-transplantation.

Results: In patients with OI (n=94), there were no differences in prior mean assay values compared with matched controls (386 versus 417 ng/ml, P=0.24). In 47 patients with AR, again no differences were detected in prior assay results (390 versus 432 ng/ml, P=0.25) when compared with controls. "Low" values (≤225 ng/ml) lacked sensitivity and specificity as a predictive test for subsequent OI, as did "strong" (≥525 ng/ml) values as a predictive test for subsequent AR.

Conclusions: Our results fail to show an association between single time point ImmuKnow assay values and the subsequent development of an adverse event in the subsequent 90 days. The optimal use of the ImmuKnow assay in kidney transplantation has yet to be determined.

Figures

Figure 1.

Distribution of TCA (ImmuKnow) results for 1330 tests performed over a 5-year period (2004 to 2009) in 583 patients.

Figure 2.

TCA (ImmuKnow) results in patients with subsequent OI compared with controls. TCA results with a subsequent OI within 90 days were compared with a control group comprised of patients without OI, matched for age and gender and with similar TCA testing within ±90 days from transplant date as patients with OI. The mean TCA values were then compared for each group.

Figure 3.

TCA (ImmuKnow) results in patients with subsequent AR compared with controls. TCA results with a subsequent AR within 90 days were compared with a control group comprised of patients without AR, matched for age and gender and with similar TCA testing within ±90 days from transplant date as patients with AR. The mean TCA values were then compared for each group.