ATC2022 in-depth interpretation (1): dd-cfDNA clinical usage scenarios and usage experience summary

As the clinical application of dd-cfDNA in kidney transplantation continues to expand, transplant centers around the world continue to deepen their understanding of the synergistic value between dd-cfDNA and the traditional gold standard renal biopsy, and continue to summarize the experience of dd-cfDNA in clinical usage scenarios and clinical benefits. Fruitful research results have emerged in the past year. This ATC has four representative studies, which we will interpret next.

First Research: Passdd-cfDNACan research reduce clinically unnecessary needle biopsies?

Research from University Hospitals Cleveland Medical Center (Cleveland, OH), USA, affirmatively answered this question.

The center has been carrying out procedural biopsies, performing puncture biopsies at four times: "zero point/before perfusion", "10-14 days after surgery", "3 months after surgery" and "12 months after surgery" of kidney transplantation. A retrospective study found that dd-cfDNA may be helpful in clinical decision-making in post-transplant DGF/SGF patients.eliminate near60%unnecessary biopsy.

Analysis of a total of 67 dd-cfDNA and pathology paired samples (7 possibly ABMR) from 55 patients showed that: 40 of them were negative with both dd-cfDNA and pathology biopsy results, 2 were dd-cfDNA positive and biopsy negative, 4 pathology showed Banff 1A rejection but dd-cfDNA results were negative, 6 pathology showed borderline rejection patients also had negative dd-cfDNA results; 6 Banff Positive dd-cfDNA and biopsy results in grade 1A or higher rejection and 2 borderline rejections[Figure 1]. If only Banff grade 1A or higher rejection was considered, the negative predictive value (NPV) of dd-cfDNA was 91.3% and the specificity was 95.5%. If critical rejection is included, the NPV of dd-cfDNA drops to 82.3%.

[Figure 1]

Second Research: Since passeddd-cfDNATesting can reduce unnecessary needle biopsies, so can it be carried out clinically?dd-cfDNAEarly screening, through referencedd-cfDNAHow to perform targeted needle biopsy based on the changes in indications of the results to improve the efficiency and profitability of pathological biopsy?

Research from the University of Maryland School of Medicine (Baltimore, MD) and other centers shows that clinically guided biopsy under dd-cfDNA monitoring can improve the 'Histological Yield and Actionable Findings' of histopathological biopsy results.

This multi-center study followed 1663 kidney transplant recipients through dd-cfDNA testing and collected a total of 540 pathological results of traditional clinically indicated biopsies and 65 pathological biopsy results guided by elevated dd-cfDNA. There were no significant differences in age, percentage of deceased donors, and post-transplantation biopsy time between groups.[Table 1]。

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dd-cfDNA-guided biopsy significantly increased the detection rate of rejection (48% vs 29%) and had fewer ATI/ATN cases (12% vs 22%) compared with traditional indication biopsy (p < 0.05)[Figure 2]. In dd-cfDNA-guided rejection biopsies (ABMR, TCMR, or mixed array), the median dd-cfDNA value was 1.46% (IQR: 1.15–2.87). Among the 267 pathological results of biopsies guided by traditional indicators but without elevated dd-cfDNA, the median dd-cfDNA value was 0.24%. Among the samples with rejection, the median dd-cfDNA value was 0.82%, and the detection value increased by 133% compared with before the rejection occurred.

[Figure 2]

Therefore,dd-cfDNATesting can add decision-making support to biopsy.Even if other clinical factors are present to guide biopsy decisions, lower dd-cfDNA values may help avoid biopsy.

Third Research： dd-cfDNACan the test detect rejection that other clinical indicators fail to indicate?

From Ochsner Foundation Hospital (New Orleans, LA), under the title 'Modern Medicine Needs Modern Technology Tools,' a report on dynamic dd-cfDNA monitoring in three kidney transplant recipients with stable creatinine confirmed the value of dd-cfDNA testing in early screening for subclinical rejection.

Case 1: DCD kidney transplantation due to ESRD secondary to HIV infection. Postoperative creatinine stabilized at 1.1 mg/dL to 1.2 mg/dL. This case underwent dd-cfDNA testing at 1, 2, 3, 4, 6, and 9 months after transplantation. The results showed that the dd-cfDNA detection value from 1 to 6 months was < 0.21%, indicating stable renal function. However, when tested at the 9th month, the dd-cfDNA value increased to 4.5%, indicating that the donor kidney may be damaged.At this time, the case’s creatinine is still stable at1.2 mg / dL， DSA IIClass weak positive. Although creatinine was stable and DSA levels were low at this time, due to the sharp increase in dd-cfDNA values, a clinical biopsy was performed, and the results suggested acute TCMR and acute ABMR.

Case 2: This is a patient with repeated kidney transplantation. The postoperative creatinine was stable at 1.0~11.3 mg/dL, and the dd-cfDNA values in the first and second months were < 0.21% and 0.32% respectively. At the 3rd month,dd-cfDNAvalue rises to0.78%，DSAis negative.This case underwent biopsy due to an elevated dd-cfDNA value, suggesting acute ABMR.[Figure 3]。

[Figure 3]

Case 3: There was a history of ESRD secondary to hypertension. Several months after renal transplantation, the patient developed acute renal failure (creatinine increased from 1.2 mg/dL to 1.7 mg/dL). Biopsy showed acute ABMR and TCMR, and he was treated. He received monthly dd-cfDNA monitoring for 1 year after transplantation. The first dd-cfDNA value was 1.9%, indicating possible kidney transplant damage. And the dd-cfDNA monitoring results show that the dd-cfDNA value is on the rise, reaching as high as 4.1%.The creatinine is stable at1.2 mg/dL-1.3 mg/dL. At this time, the biopsy showed acute ABMR and chronic active antibody rejection. This case was treated with ABMR and was treated with monthly rituximab for 6 months. During the treatment period, dd-cfDNA showed a downward trend[Figure 4]。

[Figure 4]

Fourth Research: singledd-cfDNATesting can detect early subclinical rejection, so usedd-cfDNACan combined testing with gene expression improve the detection rate of subclinical rejection?

Baystate Medical Center, Springfield, MA, USA, shared their early experience in using a combination of gene expression (TG) and dd-cfDNA (TRAC) to monitor rejection (OmniGrafs) in patients with stable renal function. Double negativity for TG and dd-cfDNA (<0.7%) excludes subclinical rejection (NPV 94%), whereas double positivity for TG and dd-cfDNA (≥0.7%) suggests the need for further clinical evaluation (PPV 89%)[Figure 5], such as needle biopsy, DSA detection, etc.

[Figure 5]

Prior to the use of OmniGraf monitoring, 13 kidney transplant recipients were continuously monitored using TG and dd-cfDNA simultaneously or separately. Further evaluation of the discordant results revealed that among the 4 negative TG/positive dd-cfDNA, 3 were positive for DSA, and only 50% of the patients were positive for proteinuria. Based on OmniGraf monitoring, 6 of 8 kidney transplant recipients avoided a procedural biopsy at 3 months after transplantation.

In this study, 35 kidney transplant recipients received 36 OmniGrafs tests. Among them, 25 cases were double negative (TG negative/dd-cfDNA negative), confirming the adequacy of immunosuppression. 10 cases were inconsistent (6 cases were TG positive/dd-cfDNA negative; 4 cases were TG negative/dd-cfDNA positive), and 1 case was double positive (TG positive/dd-cfDNA positive), requiring further examination.[Figure 6]。

[Figure 6]

The use of combined gene expression and dd-cfDNA monitoring enabled the exclusion of subclinical acute rejection without the use of needle biopsy at 3 and 12 months after transplantation, confirming the adequacy of immunosuppression and providing synergistic information to be considered alongside other clinical data such as DSA. The center believes a larger study is necessary to determine the optimal detection frequency and method for OmniGraf.

Based on the above four research results, the clinical use scenarios and experiences of dd-cfDNA detection are summarized as follows:

1. dd-cfDNA detection can reduce unnecessary puncture biopsies;

2. Biopsy guided by dd-cfDNA testing can improve the profitability and efficiency of pathological results;

3. Using dd-cfDNA or dd-cfDNA-related combination testing can detect subclinical rejection early.