Fusing modalities by multiplexed graph neural networks for outcome prediction from medical data and beyond

With the emergence of multimodal electronic health records, the evidence for diseases, events, or findings may be present across multiple modalities ranging from clinical to imaging and genomic data. Developing effective patient-tailored therapeutic guidance and outcome prediction will require fusing evidence across these modalities. Developing general-purpose frameworks capable of modeling fine-grained and multi-faceted complex interactions, both within and across modalities is an important open problem in multimodal fusion. Generalized multimodal fusion is extremely challenging as evidence for outcomes may not be uniform across all modalities, not all modality features may be relevant, or not all modalities may be present for all patients, due to which simple methods of early, late, or intermediate fusion may be inadequate. In this paper, we present a novel approach that uses the machinery of multiplexed graphs for fusion. This allows for modalities to be represented through their targeted encodings. We model their relationship between explicitly via multiplexed graphs derived from salient features in a combined latent space. We then derive a new graph neural network for multiplex graphs for task-informed reasoning. We compare our framework against several state-of-the-art approaches for multi-graph reasoning and multimodal fusion. As a sanity check on the neural network design, we evaluate the multiplexed GNN on two popular benchmark datasets, namely the AIFB and the MUTAG dataset against several state-of-the-art multi-relational GNNs for reasoning. Second, we evaluate our multiplexed framework against several state-of-the-art multimodal fusion frameworks on two large clinical datasets for two separate applications. The first is the NIH-TB portals dataset for treatment outcome prediction in Tuberculosis, and the second is the ABIDE dataset for Autism Spectrum Disorder classification. Through rigorous experimental evaluation, we demonstrate that the multiplexed GNN provides robust performance improvements in all of these diverse applications.