Digital-Reported Outcome from Medical Notes of Schizophrenia and Bipolar Patients Using Hierarchical BERT

Abstract

Patient-reported (PRO) and clinician-reported (CRO) outcomes are assessment instruments that are completed by patients and trained healthcare professionals, respectively. A PRO is a report of the direct experience of the patient with a given disease condition. A CRO is an assessment of the condition of the patient by the healthcare provider. PROs may not be accessible to all patients, especially those suffering from severe disease conditions. CROs are time-consuming and therefore administered infrequently. In the present study, we introduce a new form of assessment, the digital-reported outcome (DRO), which is automatically derived from the medical notes of the patient. DROs have a low overhead and can be generated at each patient’s visit to complement other outcome-assessment instruments and enhance clinical decision support by identifying at-risk patients. In this study, a DRO is developed to evaluate the functional impairment in the daily activities of two cohorts of patients suffering from bipolar disorder and schizophrenia. The input of the DRO is a single medical note from the electronic medical record of the patient. This note is submitted to a hierarchical bidirectional encoder representations from transformers (BERT) model. First, a sentence-level embedding is produced for each sentence in the note using a token-level attention mechanism. Second, an embedding for the entire note is constructed using a sentence-level attention mechanism. Third, the final embedding is classified using a feed-forward neural network. The model is trained to classify patients into moderate or severe functioning impairment levels according to the general assessment of functioning (GAF) scale, a CRO instrument for the assessment of the impact of mental illness on the daily activities of the patient. The DRO is validated using medical notes that were labeled by multiple healthcare providers from different healthcare institutions. The results indicate that a general DRO is able to classify patients from the two cohorts according to the two functioning impairment levels (severe versus moderate) prior to the onset of disease with an AUC of 76%. Disease-specific DROs are only applicable after the onset of the disease and produced AUCs of nearly 85%. The methodology introduced in the present paper is practical and can support the automated monitoring of the severity of the functioning impairment of bipolar and schizophrenia patients. Extending the proposed DRO to other psychiatric conditions and types of impairments is the subject of ongoing research work.