Does This Tweet Report an Adverse Drug Reaction? An Enhanced BERT-Based Method to Identify Drugs Side Effects in Twitter.

Adverse drug reactions (ADRs) are a major cause of patients' morbidity and mortality, and a source of financial burden for health systems. In this context, pharmacovigilance plays a key role, which has led to its application on social media texts, where users often report various personal health issues, including adverse drug reactions and problems with medical treatments. This new opportunity also presents new challenges, on the one hand, posts reporting ADRs are very scarce in relation to the rest of the messages, and, on the other hand, they employ colloquial language, different from the medical terminology. In this paper, we present an enhanced BERT-based method to identify tweets reporting ADRs. This method addresses the task as one of sentence-pair classification by considering some auxiliary sentences derived from the input tweets as extra contextual information. The results obtained in data from the SMM4H-2021 shared task outperformed the best results previously reported, and also show that the use of the auxiliary sentences improved the BERT results by up to 18.5%.