HL7 CDA R2 AIS Implementation Guide

HL7 Additional Information Specification Implementation GuideCDAR2AIS0000R030Figure 3.6-1 Observation Example With Pointer to Narrative TextAortic Arch Diameter 1 inch3.6.2 (OBS)Most coded information returned in an attachment will be returned using the observation entrystructure as shown above in Figure 3.6-1. Each observation represents information about asubject (usually the patient). Structurally, the attachment observations represent name-valuepairs, where the element identifies what was observed, and the element identifiesthe value of the observation. Diagnoses, measurements of any type, lab results, and studyobservations are all recorded using the observation entry structure.In the example given above, the observation of the aortic arch diameter obtained during a cardiacecho study is recorded. This observation uses the same LOINC code to identify it as is used toidentify the section where the information appears in narrative form, however, in some cases, theLOINC code will be for a different answer part.The , and elements are used as described in section 3.6.1 above.3.6.2.1 The element shall give the value of the observation. Each specific observation has arelated data type, and is indicated in the AIS data tables. Most observations will use the PQ datatype, which represents physical quantities, as shown in the example above. A physical quantityhas a real numeric value, as reflected in the value attribute of the element, and units ofmeasure, shown in the units attribute on that element. The units of measure are specified usingthe Unified Code for Units of Measure (UCUM). This code system supports reporting all units ofmeasures being contemporarily used in international science, engineering, and business.Page 50March 2007Copyright © 1998-2007Health Level Seven, Inc. All rights reserved.Release 3.0 Draft Standard