Overview | Laboratory Tests

Logic Observation Identifiers Names and Codes (LOINC) is a standard for identifying medical laboratory observations. Lab results in i2b2 are driven by LOINC codes associated with lab tests within the medical record system. For each lab result we have identified whether or a not a result is a numeric, textual, or flag value to provide maximum query flexibility. Over time, as new tests are resulted within the UNCHCS laboratories, new codes will be added. Most common labs have an associated LOINC code at this point in time—however, there are some tests that are not yet LOINC coded. These tests are not available in i2b2, but may be available in the CDW-H by request.

Numeric versus Text Results

Lab results can be reported in either a textual field or a numeric field. When the result included both numeric and textual fields together in i2b2@UNC, we strived to separate them. For example, (i.e. ’55 ng/mL’) from textual fields and converted them into numeric values (’55’) and the related unit of measure (‘ng/mL’). However, there are many tests that only support text values (i.e. ‘POSITIVE’,’NEGATIVE’, etc.) or support either a numeric or text value depending on the result .

Text Value Mapping
To simplify text value searching we developed a set of textual mappings to convert similar text results into a single harmonized value. As an example, (“pos,” “POS,” and “Pos”) have all been mapped to the single term “Positive.” The mappings were done in a manner to ensure that the meaning of the result was not lost.

Units of Measure
Units of measure is a tricky area, as some numeric lab results can be expressed in multiple different units with potentially complex conversion factors. To accommodate the various units of measure that could be associated with a specific lab test, multiple concepts may exist for a single lab test that are suffixed with a different unit of measure.