Validation of a rapid type 1 diabetes autoantibody screening assay for community-based screening of organ donors to identify subjects at increased risk for the disease

Abstract

The Network for Pancreatic Organ donors with Diabetes (nPOD) programme was developed in response to an unmet research need for human pancreatic tissue obtained from individuals with type 1 diabetes mellitus and people at increased risk [i.e. autoantibody (AAb)-positive] for the disease. This necessitated the establishment of a type 1 diabetes-specific AAb screening platform for organ procurement organizations (OPOs). Assay protocols for commercially available enzyme-linked immunosorbent assays (elisas) determining AAb against glutamic acid decarboxylase (GADA), insulinoma-associated protein-2 (IA-2A) and zinc transporter-8 (ZnT8A) were modified to identify AAb-positive donors within strict time requirements associated with organ donation programmes. These rapid elisas were evaluated by the international islet AAb standardization programme (IASP) and used by OPO laboratories as an adjunct to routine serological tests evaluating donors for organ transplantation. The rapid elisas performed well in three IASPs (2011, 2013, 2015) with 98-100% specificity for all three assays, including sensitivities of 64-82% (GADA), 60-64% (IA-2A) and 62-68% (ZnT8A). Since 2009, nPOD has screened 4442 organ donors by rapid elisa; 250 (5·6%) were identified as positive for one AAb and 14 (0.3%) for multiple AAb with 20 of these cases received by nPOD for follow-up studies (14 GADA+, two IA-2A(+) , four multiple AAb-positive). Rapid screening for type 1 diabetes-associated AAb in organ donors is feasible, allowing for identification of non-diabetic, high-risk individuals and procurement of valuable tissues for natural history studies of this disease.

Keywords: autoantibodies; nPOD; organ donor; screening; type 1 diabetes.

Figure 1

Receiver operating characteristic (ROC) curve analyses are shown for (a) glutamic acid decarboxylase (GADA), (b) insulinoma‐associated protein‐2 (IA‐2A) and (c) zinc transporter 8 (ZnT8A). Plots are 100 – specificity % (x‐axis) versus sensitivity % (y‐axis). The following cut‐offs were selected to maximize specificity: (a) 20 IU, 98% specificity and 70% sensitivity [area under the curve (AUC) = 0·88], (b) 60 IU, 99% specificity and 63% sensitivity (AUC = 0·80 and (c) 20 IU, 97% specificity with 57% sensitivity (AUC = 0·75).

Figure 2

Overview of the Network for Pancreatic Organ donors with Diabetes (nPOD) autoantibody against insulin (AAb) screening programme over time. The overall concordance of the screening enzyme‐linked immunosorbent assay (elisa) with nPOD elisa core laboratory is shown for glutamic acid decarboxylase (GADA) (blue line), IA‐2A (green line) and zinc transporter 8 (ZnT8A) (black line; left y‐axis). The number of total subjects screened (bars) and those screened under 30 years of age (filled bars) are shown (right y‐axis). Changes to the programme are indicated with text box and arrows for each new event above the graph.

Figure 3

Venn diagrams are shown comparing the enzyme‐linked immunosorbent assay (elisa) (left) with the radiobinding assay (RBA) (right) results for glutamic acid decarboxylase (GADA) (top), insulinoma‐associated protein‐2 (IA‐2A) (middle) and zinc transporter 8 (ZnT8A) (bottom) within the various categories of organ donors. The RBA is set as the gold standard, upon which the autoantibody against insulin (AAb) status is determined.

Figure 4

Screening serum sample versus the organ recovery serum sample results by (a,b) enzyme‐linked immunosorbent assay (elisa) and (c,d) radiobinding assay (RBA) are compared for (a,c) glutamic acid decarboxylase (GADA) and (b,d) insulinoma‐associated protein‐2 (IA‐2A).