An Experimental Approach to Risk of Organ Rejection: Demonstration of False Immunosuppressant Results Due to Radiopaque Agents

Background: Immunosuppressant blood levels should be measured at regular periods in order to keep them within the therapeutic index. Although LC-MS/MS is preferred as a reliable method, some molecules like radiopaque agents in blood matrix may lead to false results. The aim of this study is to investigate the effect of seven different radiopaque agents on immunosuppressant drugs. Methods: Seven different radiopaque agents were added into control materials containing tacrolimus, everolimus, sirolimus and cyclosporine A drugs. Measurements were performed by LC-MS/MS instrument. The amount of deviations from target values were calculated. Results: Immunosuppressant blood levels significantly changed after the administration of radiopaque agents. Seven different radiopaque products led to false negative results in tacrolimus and cyclosporine A levels at a rate of 19.77% to 44.45%. The smallest deviations were seen in everolimus levels with administration of RM6 (gadodiamide) and in sirolimus levels with RM1 (gadobutrol) at rates of 4.04% and 2.11%, respectively. The highest deviations were observed with RM3 (iohexol) administration in everolimus and sirolimus levels at rates of 153.72% and 171.41%, respectively. Conclusions: False immunosuppressant results associated with radiopaque agents may result in organ rejection. Preferring radiopaque agents that cause the least interference risk is important to reduce the organ rejection risk. However, the least risky method is to obtain samples for drug levels before contrast-enhanced imaging.