Biomarkers—A Potential Route for Improved Diagnosis and Management of Ongoing Renal Damage

Currently, the identification and validation of biomarkers of kidney injury is among the top priorities of many diagnostic biotechnology companies as well as academic research institutes. Specifically, in renal transplantation, validated biomarkers of tissue injury with good discriminatory power between the various renal compartments and the underlying pathophysiology are desired, because sequential allograft biopsies are limited in number and cannot be used as a screening tool. Given the high demands on these markers, it is not surprising that none of those currently under evaluation has been thoroughly validated for a specific entity. Published biomarker candidates for early tubular damage include neutrophil gelatinase-associated lipocalin (NGAL), interleukin (IL)-18, soluble CD30, perforin, and granzyme B. Recently, C4d flow panel reactive antibodies were evaluated as biomarkers for humoral alloimmune responses. Additional biomarkers such as FOXP3 and kidney injury molecule 1 have been studied in the maintenance phase of renal transplantation. Given the complex prerequisites, it is not surprising that no biomarker panel has been sufficiently validated for clinical use. However, in the near future a biomarker for use as an indicator of renal tubule cell injury will be available. Troponin T or transaminase of the kidney may then at least be used to differentiate between functional renal failure (equivalent to a rise in creatinine) and intrinsic kidney injury.