Table 1
Comparison of donor-derived cell-free DNA, gene expression profiling, and donor-specific antibodies for cardiac graft rejection.
| FEATURE | DONOR-DERIVED CELL-FREE DNA (DD-CFDNA) | GENE EXPRESSION PROFILING (GEP) | DONOR-SPECIFIC ANTIBODIES (DSA) |
|---|---|---|---|
| Utility | Detects both ACR and AMR by measuring donor-derived DNA fragments in plasma | Evaluates immune activation by analyzing gene expression in PBMCs for ACR detection | Identifies AMR risk by detecting antibodies against donor HLA antigens |
| Sensitivity | Up to 81% for ACR and AMR detection | 37.5-50% depend on study and threshold | Sensitivity varies widely for AMR detection |
| Specificity | 85% specificity; NPV > 97% at thresholds > 0.15-0.2% | 73-89% specificity; NPV > 98% for ACR ≥ 2R exclusion with score > 30 | Low specificity; not reliable as a stand-alone test for rejection |
| Advantages | Noninvasive, sensitive, and specific, detects graft injury before clinical signs | Noninvasive, high NPV, widely available | Useful for AMR risk stratification; inexpensive and widely available |
| Disadvantages | Limited by cost, availability, and false positives due to ischemia or procedural trauma | Low sensitivity for AMR; influenced by infection, inflammation, and steroid use | Limited specificity, transient elevations may not indicate true rejection |
| Pitfalls in Results | False positives from ischemia, biopsy-induced injury, or infections; false negatives from chimerism | False positives due to infections, non-transplant-related inflammation, or high-dose steroids | False positives due to non-rejection immune responses; confounded by prior sensitization |
| Landmark Trials | GRAfT and D-OAR | CARGO, CARGO II, and IMAGE trials | |
| ISHLT 2023 guidelines recommendations |
| ||
[i] ACR: acute cellular rejection; AMR: antibody mediated rejection; PBMC: peripheral blood mononuclear cells; EMB: endomyocardial biopsy; NPV: negative predictive value; HLA: human leukocyte antigen; GRAfT: genomic research alliance for transplantation study; D-OAR: donor-derived cell-free dna-outcomes allomap registry; CARGO: cardiac allograft rejection gene expression observational study; IMAGE: invasive monitoring attenuation through gene expression study; eIMAGE: early invasive monitoring attenuation through gene expression study; ISHLT: International Society for Heart and Lung Transplantation
Table 2
Interpretation of gene expression profiling and donor-derived cell-free DNA (dd-cfDNA) results from the D-OAR Study Cohort.
| GEP/DD-CFDNA COMBINATION | D-OAR STUDY RESULT INCIDENCE | RESULT INTERPRETATION | CLINICAL IMPLICATIONS |
|---|---|---|---|
| Low GEP/low dd-cfDNA | 56% | High probability that the patient does not have acute rejection ACR > 99% NPV AMR 98% NPV | Reduce frequency of scheduled EMB |
| High GEP/low dd-cfDNA | 26% | Early ACR Consider potential reasons for false positive GEP such as CMV infection or changes in immunosuppression regimen | Check steroid dose and adherence Evaluate for active CMV infection.Repeat testing earlier than protocol |
| Low GEP/high dd-cfDNA | 11% | Early cellular rejection Antibody-mediated rejection (AMR) Consider potential reasons for false positive dd-cfDNA such as myocardial injury and CAV | Repeat EMB Review ancillary tests, eg, echocardiogram, DSA, troponin, nt-proBNP |
| High GEP/high dd-cfDNA | 6% | High probability that rejection injury is present (~20% PPV) | Rejection workup, including EMB, DSA, echocardiogram and consider cardiac MRI |
[i] ACR: acute cellular rejection; AMR: antibody mediated rejection; EMB: endomyocardial biopsy; NPV: negative predictive value; PPV: positive predictive value; D-OAR: donor-derived cell-free dna-outcomes allomap registry; CMV: cytomegalo virus; CAV: cardiac allograft vasculopathy; DSA: donor-specific antibodies; NT-proBNP: N-terminal pro-brain natriuretic peptide