Spuriously low immunosuppressant results due to incomplete hemolysis – A pitfall in transplant patient therapeutic drug monitoring

Abstract

Objective: Therapeutic drug monitoring (TDM) plays a crucial role in transplantation medicine when it comes to immunosuppressants like Tacrolimus, Cyclosporine A, Sirolimus, and Everolimus. The analysis involves using immunometric or mass spectrometric methods on whole blood samples. Hemolysis of the samples is necessary for the assessment. Typically, this is accomplished through manual protein precipitation using pre-treatment reagents, followed by vigorous vortex mixing and subsequent centrifugation. It is important to note that omitting the vortex step in these manual procedures can be seen as a potential procedural error. Methods: To assess the potential impact of omitting the vortex step, an experiment was conducted. Clinical samples were divided into two aliquots, which were then analyzed comparatively. In one group of aliquots, the vortex step was intentionally omitted, while the other followed the correct execution of the test. Results: The non-vortex-mixed samples showed significantly erroneous low results for all analytes. Conclusion: Omitting or inadequately performing vortex mixing during the hemolysis procedure can be considered as a significant potential source of analytical error in TDM of immunosuppressants.