| _text | string | Search on the narrative of the resource |  | 
| _content | string | Search on the entire content of the resource |  | 
| _id | token | Logical id of this artifact | Resource.id | 
| _lastUpdated | date | When the resource version last changed | Resource.meta.lastUpdated | 
| _profile | uri | Profiles this resource claims to conform to | Resource.meta.profile | 
| _query | token | A custom search profile that describes a specific defined query operation |  | 
| _security | token | Security Labels applied to this resource | Resource.meta.security | 
| _source | uri | Identifies where the resource comes from | Resource.meta.source | 
| _tag | token | Tags applied to this resource | Resource.meta.tag | 
| broker | reference | MessageTopic broker. | MessageTopic.broker | 
| Topic | token | MessageTopic topic id. | MessageTopic.topicId | 
| _iguhealth-author | reference | The author of the resource | Resource.meta.extension.where(url='https://iguhealth.app/author').value | 
| _type | token | Missing in search-parameter.json for R4 this is derived from the R4B Definition |  |