From the Guidelines
The most reliable test for diagnosing early or subclinical acute rejection is US-guided biopsy [ 1 ]. This method is considered the standard for diagnosis of rejection and evaluation of immunosuppression, as it allows for direct examination of the graft tissue.
Key Points
- US-guided biopsy has a low complication rate, with a reported rate of 0.4% to 1% graft loss in approximately 2,500 biopsies [ 1 ].
- Other imaging modalities, such as duplex Doppler US, have limited sensitivity and specificity in identifying the cause of functional transplant dysfunction [ 1 ].
- Renal segmental or intralobar artery resistive indices (RI), measured by duplex Doppler US, are not reliable in identifying the cause of functional transplant dysfunction, with a sensitivity of 13% and a specificity of 100% [ 1 ].
- CT and CTA may be useful in evaluating renal masses, perinephric fluid collections, and posttransplant lymphoproliferative disease, but have limited data on their usefulness in evaluating transplant vascular complications [ 1 ].
From the Research
Diagnostic Biomarkers for Early or Subclinical Acute Rejection
The most reliable test for diagnosing early or subclinical acute rejection involves the use of biomarkers that can detect kidney injury at an early stage. Some of the key biomarkers that have been identified include:
- Kidney Injury Molecule-1 (KIM-1) 2, 3, 4, 5, 6
- Urinary N-acetyl-beta-glucosaminidase (NAG) 2
- Glycosuria 2
- Proteinuria 2
- Plasma creatinine 2, 3
- Blood urea nitrogen (BUN) 2, 3
Sensitivity and Specificity of KIM-1
KIM-1 has been shown to be a highly sensitive and specific biomarker for kidney injury, with studies demonstrating its ability to detect early kidney damage in various forms of nephrotoxic injury, cardiac surgery-induced kidney injury, transplant rejection, and chronic kidney diseases 3, 5. The use of KIM-1 as a biomarker has been qualified by the Food and Drug Administration and European Medicines Agency for monitoring drug-induced kidney injury in preclinical studies and on a case-by-case basis in clinical trials 3.
Rapid Detection Methods for KIM-1
Several rapid detection methods for KIM-1 have been developed, including:
- Enzyme-linked immunosorbent assay (ELISA) 2, 4, 6
- Microbead-based assay 3
- Immunochromatographic lateral flow assay 3, 4
- Colloidal gold immunochromatographic strip 4
Clinical Applications of KIM-1
KIM-1 has been shown to be a valuable biomarker for the early diagnosis of obstructive acute kidney injury, with studies demonstrating its ability to detect kidney injury at an early stage 4. The use of KIM-1 as a biomarker may also have implications for the diagnosis and monitoring of other kidney diseases, including transplant rejection and chronic kidney diseases 5, 6.