Complement-Activating DSA: Which Assay in Which Setting?
Imperial College Renal &
Transplant Centre, Hammersmith Hospital, London, United Kingdom
Meeting: 2013 American Transplant Congress
Abstract number: 354
The presence of pre-formed and de novo donor specific antibodies [DSA] are associated with an increased incidence of antibody mediated rejection [AMR] and graft loss [GL]. We and others have shown particularly poor outcomes in patients with DSA capable of activating the classical pathway of complement [C’-activating].There are two methods of detecting C’-activating DSA using Luminex, either by detecting the C’ fragment C4d covalently bound to the microsphere, or C1q bound to the Fc portion of DSA.
Both methods involve a second-layer modification to the standard Luminex technique utilising a fluorescent labelled dye [Dylight-549 labelled anti-C4d or Phycoerythrin labelled anti-C1q]. To our knowledge there are no studies directly comparing the two techniques.
We undertook this study to compare the two methods for detecting C’activating DSA in 122 renal transplant recipients with DSA [52 pre-formed, 70 de novo]. All patients were transplanted with Alemtuzumab induction, steroid sparing and tacrolimus monotherapy. Rejection was diagnosed by indication biopsy according to Banff criteria. Graft survival, antibody mediated rejection and Receiver Operator Characteristic curve [ROC AUC] analysis was used to compare the two methods.
In patients with low level pre-formed DSA the C4d assay was superior to the C1q assay for the prediction of GL and AMR.
| Graft Survival | AMR-Free Survival | ||||||
| n(%) | 1 Yr (%) | 3 Yr (%) | AUC | 1 Yr (%) | 3 Yr (%) | AUC | |
| C1q + | 12 (30) | 83 | 74 | 58 | 58 | ||
| C1q – | 40 (70) | 98 | 89 | 0.561 | 80 | 78 | 0.567 |
| C4d + | 12 (30) | 83 | 75 | 42 | 42 | ||
| C4d – | 40 (70) | 98 | 88∗ | 0.630 | 85 | 82† | 0.679 |
In patients who developed de novo DSA however the C1q assay outperformed the C4d assay for the prediction of GL and AMR.
| Graft Survival | AMR-Free Survival | ||||||
| n (%) | 1 Yr (%) | 3 Yr (%) | AUC | 1 Yr (%) | 3 Yr (%) | AUC | |
| C1q + | 23 (33) | 83 | 64 | 65 | 40 | ||
| C1q – | 47 (67) | 94 | 90° | 0.723° | 85 | 72∗ | 0.661∗ |
| C4d + | 39 (41) | 83 | 65 | 68 | 44 | ||
| C4d – | 41 (59) | 95 | 92∗ | 0.671 | 85 | 71 | 0.588 |
In our hands the C4d assay is the test of choice for detecting C’-activating DSA patients with low level pre-formed DSA and predicts AMR with a sensitivity of 0.5 and specificity of 0.85. In contrast the C1q assay is the test of choice for detecting C’-activating DSAb in patients with de novo DSAb and predicts AMR with a sensitivity of 0.69 and specificity of 0.75. It is possible that difference between the two assays is due to technical aspects which may be overcome by adaptations to the protocol.
Lawrence, C.: Other, OneLambda, Have Received Support To Attend Conferences.
To cite this abstract in AMA style:
Lawrence C, Willicombe M, Brookes P, Santos-Nunez E, Roufosse C, Warrens A, Taube D. Complement-Activating DSA: Which Assay in Which Setting? [abstract]. Am J Transplant. 2013; 13 (suppl 5). https://atcmeetingabstracts.com/abstract/complement-activating-dsa-which-assay-in-which-setting/. Accessed May 14, 2025.« Back to 2013 American Transplant Congress