Practise vocabulary for HL7 v2 message structure, segments (MSH, PID, OBX), acknowledgments, and integration engines.
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An HL7 v2 ADT^A01 message indicates:
HL7 v2 message type format: Application^Event. ADT = Admit/Discharge/Transfer application; A01 = patient admitted. Other ADT events: A02 (transfer), A03 (discharge), A08 (update patient info). Healthcare systems listen for ADT messages to sync patient demographics.
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The MSH (Message Header) segment in an HL7 v2 message contains:
Every HL7 v2 message starts with MSH. Key fields: MSH.3 (Sending Application), MSH.4 (Sending Facility), MSH.5 (Receiving Application), MSH.9 (Message Type), MSH.10 (Message Control ID — unique ID for acknowledgment), MSH.12 (HL7 version).
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The PID (Patient Identification) segment provides:
PID is the most referenced segment in HL7 v2. PID.2 (Patient ID), PID.3 (Patient Identifier List — MRN), PID.5 (Patient Name: family^given^middle), PID.7 (Date of Birth), PID.8 (Sex), PID.11 (Address). Patient matching uses PID fields.
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An ACK (Acknowledgment) message with an AA (Application Accept) code means:
HL7 v2 acknowledgment codes: AA (Application Accept — success), AE (Application Error — received but processing failed), AR (Application Reject — message not accepted, usually due to a structural issue). The sending system must retry on AE/AR depending on the error type.
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MLLP (Minimal Lower Layer Protocol) in healthcare integration means:
MLLP (also called LLP) is the default HL7 v2 transport over TCP. Unlike HTTP, it was designed for persistent TCP connections with low latency. Most integration engines (Mirth Connect, Rhapsody, Azure Integration Services) support MLLP listeners.
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An integration engine in healthcare IT is used to:
Integration engines (Mirth Connect, Rhapsody, Cloverleaf, Azure Health Data Services) are the middleware layer in healthcare IT. They listen for messages, apply transformation rules, route to multiple destinations, and handle errors and logging — essential for connecting dozens of incompatible clinical systems.