Identifying sub-phenotypes of acute kidney injury using structured and unstructured electronic health record data with memory networks

Acute Kidney Injury (AKI) is a common clinical syndrome characterized by the rapid loss of kidney excretory function, which aggravates the clinical severity of other diseases in a large number of hospitalized patients. Accurate early prediction of AKI can enable in-time interventions and treatments. However, AKI is highly heterogeneous, thus identification of AKI sub-phenotypes can lead to an improved understanding of the disease pathophysiology and development of more targeted clinical interventions. This study used a memory network-based deep learning approach to discover AKI sub-phenotypes using structured and unstructured electronic health record (EHR) data of patients before AKI diagnosis. We leveraged a real world critical care EHR corpus including 37,486 ICU stays. Our approach identified three distinct sub-phenotypes: sub-phenotype I is with an average age of 63.03 +/- 17.25 years, and is characterized by mild loss of kidney excretory function (Serum Creatinine (SCr) 1.55 +/- 0.34 mg/dL, estimated Glomerular Filtration Rate Test (eGFR) 107.65 +/- 54.98 mL/min/1.73 m(2)). These patients are more likely to develop stage I AKI. Sub-phenotype II is with average age 66.81 +/- 10.43 years, and was characterized by severe loss of kidney excretory function (SCr 1.96 +/- 0.49 mg/dL, eGFR 82.19 +/- 55.92 mL/min/1.73 m(2)). These patients are more likely to develop stage III AKI. Sub-phenotype III is with average age 65.07 +/- 11.32 years, and was characterized moderate loss of kidney excretory function and thus more likely to develop stage II AKI (SCr 1.69 +/- 0.32 mg/dL, eGFR 93.97 +/- 56.53 mL/min/1.73 m(2)). Both SCr and eGFR are significantly different across the three sub-phenotypes with statistical testing plus postdoc analysis, and the conclusion still holds after age adjustment.