Developers Getting Started With i2b2
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Unit Conversion for Numerical Observations

In the OBSERVATION_FACT table the UNIT_CD column stores the unit value for your numerical observations. An example of a value in UNIT_CD would be mg for milligram or gm for gram.

Although i2b2 recommends the units be normalized to a single unit we also recognize this is not always possible. In this instance, you may wish to have the units converted automatically when running a query in which a value constraint is defined. To turn this feature on you would add the following parameter to the Project you want it applied.

Type of Parameter: Project Parameter





Enables unit conversion


Disables unit conversion (default setting)


The parameter does not change the data stored in the database. It is simply applied when the query is run.

For steps on how to add a project parameter please see the section titled Add Project Parameters located in this chapter.