Concept Dictionary

A concept dictionary is a collection of coded, unique concepts used to generate forms and encode data within the system. In our concept dictionary, just about every medical concept we use is defined within the dictionary. This is done in lieu of hardcoding concepts into tables.

For example, consider the following format of data:

Date	Patient	Sodium	Creatinine	Urine Color
Monday	Smith		1.5	yellow
Wednesday	Jones	142	0.7

This is easy to understand, but what happens when you decide to store glucose levels? You must change the structure of your table. And -- heaven forbid -- what if the lab starts reporting creatinines with a new reference range? Do you throw the new creatinine values in the same column and worry about it later? Or do you end up a second creatinine column for the new values?

Now consider the same data in the following format:

Date	Patient	Observation	Value
Monday	Smith	Creatinine	1.5
Monday	Smith	Urine Color	yellow
Wednesday	Jones	Sodium	142
Wednesday	Jones	Creatinine	0.7

This format is slightly hard to grasp at first. Now there is one row per value instead of one per patient. Rather than being text, the various observations are actually referenced from a central concept dictionary. If the lab starts reporting a new type of creatinine, you no longer have to change the structure of the table. You simple add a concept for the new creatinine into your concept dictionary and you are done.

Paul made a great Concept Dictionary Guidelines document early on during the development of the OpenMRS