HL7 QAK Query Acknowledgment
HL7 field reference QAK fields from HL7 v2.5.1 Show fields
These are the generated fields for the version selected at the top of the page. The document stays the same, but the reference panel follows that version.
Fields
QAK acknowledges a query and tells the requester whether the response succeeded, failed, or needs different handling.
The standard describes QAK this way: The QAK segment contains information sent with responses to a query. The QAK segment may appear as an optional segment placed after the (optional) ERR segment in any query response (message) to any original mode query.
Query segments define what the sender is asking for, how the receiver should format the answer, and how a multi-message response is continued or limited.
A query is an interface contract. The tag, parameters, row definitions, sort/filter rules, and continuation pointers must match exactly or the receiver may return technically valid data that is not what the requester expected.
The v2.5.1 structures show QAK in ADR_A19 - Patient query, DOC_T12 - Document query, DSR_Q01 - Query sent for immediate response, and DSR_Q03 - Deferred response to a query, and 29 other message structures. That tells you where it can appear, but the implementation guide still decides which optional fields are meaningful.
For practical interface work, read the generated field panel for datatype, required, repeatable, and table details, then use the notes below to decide what the field should mean in the receiving workflow.
QAK-1 is the requester's handle for this query. Echoing it back correctly is what lets the requester match a response to the question it asked.
QAK-2 tells the receiver the state of this query workflow. Status fields often drive workflow branches, so use the agreed code and do not infer a status just because another field looks complete.
The coded value should follow HL7 table 0208 or the narrower table in the local profile.
QAK-3 names the query, event, stored procedure, virtual table, or profile being invoked. This is the semantic switch for the query, so both sides need to agree on the allowed names and their parameter rules.
QAK-4 is used for reconciliation. The receiver may compare it with the segments, batches, messages, rows, or items actually received, so do not populate it from a stale estimate.
QAK-5 carries This payload for this query workflow. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
QAK-6 carries Hits remaining for this query workflow. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.