**Definition:**The set of LOINC codes for the act of determining the period of time that has elapsed since an entity was born or created.
http://terminology.hl7.org/CodeSystem/v3-ActCode| Code | Display | |
| 21611-9 | age patient qn est | **Definition:**Estimated age. |
| 21612-7 | age patient qn reported | **Definition:**Reported age. |
| 29553-5 | age patient qn calc | **Definition:**Calculated age. |
| 30525-0 | age patient qn definition | **Definition:**General specification of age with no implied method of determination. |
| 30972-4 | age at onset of adverse event | **Definition:**Age at onset of associated adverse event; no implied method of determination. |