A code that provides additional detail about the means or technique used to ascertain the observation. Examples: Blood pressure measurement method: arterial puncture vs. sphygmomanometer (Riva-Rocci), sitting vs. supine position, etc. OpenIssue: Description copied from Concept Domain of same name. Must be verified. Note that the Domain has a full discussion about use of the attribute and constraining that is not appropriate for the code system description. Needs to be improved.