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Web-scale pharmacovigilance. Maggie Mahan 16 April 2013. Motivation. Adverse drug events cause morbidity & mortality Typically discovered after drug marketed Increased internet searches of health information (~60% of American adults)
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Web-scale pharmacovigilance Maggie Mahan 16 April 2013
Motivation • Adverse drug events cause morbidity & mortality • Typically discovered after drug marketed • Increased internet searches of health information (~60% of American adults) • Mining web search history to identify unreported side effects of drugs or drug combinations • Logs are inexpensive to collect & mine • Drug safety surveillance
Background (1/2) • Drug side effects reported but incomplete and biased • Leads to delayed reporting of adverse events • Compounded with multiple drugs • Previous research on tracking seasonal influenza • Search logs can be used for health monitoring • Health-seeking activity captured in queries to web search services mirrors trends gathered by traditional surveillance
Background (2/2) • Present study used online health-seeking search activity to identify adverse drug events associated with drug interactions • Paroxetine: anti-depressant • Pravastatin: cholesterol-lowering drug • Interaction reported to create hyperglycemia • Hypothesis: patients taking these two drugs might experience symptoms of hyperglycemia and may have conducted internet searches on these symptoms and concerns related to hyperglycemia before the association was reported
Methods • 12 months of search logs • Word used in user queries • Pravastatin & brand names • Paroxetine & brand names • Hyperglycemia-associated words • Disproportionality analysis • Assess increased chance of search for hyperglycemia-related terms given search for both drugs • Reporting ratios based on observed versus expected
Results – user groups & prevalence • Searching both drugs = more likely to search hyperglycemia-associated terms • Difference between groups is consistent
Results - disproportionality analysis for known drug–drug interactions
Conclusions • Log analysis valuable for identifying drug pairs linked to hyperglycemia • Method generalizable, similar to a prediction task • Majority of TP identified provides validation for the set of terms used • Valuable signal even though search logs are unstructured, not necessarily related to health, and include any words entered by users • More in-depth analysis is needed • Patient search behavior directly can complement traditional sources of data for pharmacovigilance
References • White RW, Tatonetti NP, Shah NH, Altman RB, Horvitz E (2013) Web-scale pharmacovigilance: listening to signals from the crowd. J Am Med Infom Assoc. 20(3): 404-408. • http://scopeblog.stanford.edu/2013/03/06/researchers-mine-internet-search-data-to-identify-unreported-side-effects-of-drugs/