Introduction: Immunosuppressive drugs are used to suppress the immune system and to prevent transplanted organ rejection. Because of their narrow therapeutic index, potent immunosuppressive effects and long-life administration, therapeutic drug monitoring of patients is required to ensure the efficacy of treatment and minimal toxic side effects. The aim of the current study is to perform a critical analysis of the literature for determination of immunosuppressants in clinical practice.
Materials and Methods: Using the online databases Scopus, PubMed and Google Scholar a search with the keywords `immune methods for immunosuppressants`, `LC-MS for immunosuppressants`, `immunosuppressant therapeutic monitoring` was conducted. More than 20 000 results published since 2012 were found. Filters like `free full text` and `review article type` were applied.
Results: Two basic methods for immunosuppressant analysis are currently used: immunochemical and chromatographic. Immunoassays are widely used in the clinical laboratory practice. Some of their major limitations are the significant cross-reactivity with various metabolites of these drugs, leading to up to 50% positive bias, inability to simultaneously measure two or more immunosuppressants, and relatively high cost. The liquid chromatographic techniques, especially with mass-selective detection provide higher specificity and simultaneous analysis. The possibility of chromatography to be combined with alternative sampling techniques such as oral fluid, dried blood spots makes it an even more reliable alternative to immunochemical methods. Moreover, during the last years ready-made kits for chromatographic analysis have been developed to minimize the inter-laboratory bias.
Conclusion: Liquid chromatographic methods have been considered the gold standard in analytical techniques for therapeutic monitoring of immunosuppressants, because of their robustness, selectivity and accuracy.
