Electronic health record (EHR) data are like an iceberg. The part researchers can readily see and access is only a fraction of the total data available, because most of the details are hidden away in the free text notes. In fact, it has been estimated that around 80% of all clinical data are found within the free text in the EHR (also see: here). There are multiple reports and studies that have demonstrated the importance of using EHR free text. In fact, utilizing only the structured data can lead to erroneous conclusions or missed patients when recruiting for trials.
Below is a list of representative quotes from various studies that illustrate the issue.