I say this because this problem is vastly more complicated than people believe for the following reasons:
* A substantial amount of data about patients is encapsulated in clinical notes which are free text. There is no standard format for notes; notes wildly vary in terms of quality, detail, and accuracy; and notes are full of non-standard abbreviations and clinical shorthand.
* A large amount of the data in an EHR is incomplete or incorrect. Information may be out of date or recorded incorrectly. Patient medication lists are a great example of this, and they frequently cannot be trusted by physicians even during the course of a single hospital stay (medications are started or discontinued without being properly recorded). Then there is the issue of non-adherence: patients frequently claim to be adherent to treatment regimens that they are not actually adherent to which is going to distort outcome data. In fact, the majority of people are non-adherent for many different treatment regimens. More generally, diagnoses may have been incorrectly determined and data may be incorrectly labeled or missing.
* Data exists all over the place even within an EHR, let alone across facilities. I myself have been to at least 5-10 hospitals and more outpatient clinics over my life, none of whom share data with each other. No one entity has all the relevant data about a patient, including insurers, specific care teams, or the hospital systems they got this data from.
* Data placed into a EHR may be intentionally falsified for simplicity or to get insurance coverage. It is not uncommon for physicians to intentionally misdiagnose a patient so their insurance will cover a diagnostic / treatment / procedure, or to input a less specific diagnostic code to save time when a more specific one is available.
Trying to train with data sets this fucked up is an enormous challenge.