Different facilities and doctors use different terminology to describe the same things which makes the exchange of patient data difficult:

Until the data is normalized, the true potential of HIEs will be stunted. That potential lies in the ability to instantaneously act on the exchanged information. Ideally, two doctors sharing the same patient will be able to automatically absorb each other’s separate patient data.

via Health Information Exchanges Lack Standards – Healthcare –.

Providers used to jot down their diagnosis on a paper chart. Today, diagnoses are entered into an electronic medical record (EMR) and then may be transferred between providers – where the method of encoding the data is different. This problem is far more challenging than it seems on the surface (having studied graduate medical informatics, I have been introduced to the complexity).

Coldstreams