  The International Classification of Diseases (ICD) is an authoritative
medical classification system of different diseases and conditions for clinical
and management purposes. ICD indexing assigns a subset of ICD codes to a
medical record. Since human coding is labour-intensive and error-prone, many
studies employ machine learning to automate the coding process. ICD coding is a
challenging task, as it needs to assign multiple codes to each medical document
from an extremely large hierarchically organized collection. In this paper, we
propose a novel approach for ICD indexing that adopts three ideas: (1) we use a
multi-level deep dilated residual convolution encoder to aggregate the
information from the clinical notes and learn document representations across
different lengths of the texts; (2) we formalize the task of ICD classification
with auxiliary knowledge of the medical records, which incorporates not only
the clinical texts but also different clinical code terminologies and drug
prescriptions for better inferring the ICD codes; and (3) we introduce a graph
convolutional network to leverage the co-occurrence patterns among ICD codes,
aiming to enhance the quality of label representations. Experimental results
show the proposed method achieves state-of-the-art performance on a number of
measures.
