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In the Observation_fact table of the Clinical Research Chart of i2b2, the following columns are used to describe values associated with concepts:

ValueType     ValueType_CD (Varchar(50))

NVal     NVal_num (number)

TVal     TVal_char (Varchar(255) – standard, sized per implementation)

ValueFlag     ValueFlag_CD (Varchar(50))

Quantity     Quantity_CD (number)

Units     Units_CD (Varchar(50))

Observation     Observation_blob (blob)

Values that are expected to occur in these columns are specified in a column of the Ontology Cell named "Metadata_XML".  Modifiers may often have values associated with them, and the above columns are filled and the Metadata_XML is specified in the same way as the concept_cd, however the value applies to the modifier rather than the concept_cd.  When there is a value in these columns and a modifier is present in the modifier_cd column, the value ALWAYS applies to the modifier_cd coded element.  Note that if the value is desired to apply to the base concept_cd, the modifier_cd column is specified to be "@".

Values are defined according to the ValueType_CD column, which can be construed as an identifier for the type of value object that fills out the rest of the above columns.   There are two identifiers that are used for medication modifiers:

N      N = numeric value

T      T = enumerated or string value

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