Written by Technical Team | Last updated 31.07.2025 | 5 minute read
Digital transformation within the NHS and wider healthcare landscape has created a growing demand for robust, interoperable systems that ensure the seamless flow of patient information across services. At the heart of many NHS Trusts’ digital ecosystems is System C’s CareFlow Electronic Patient Record (EPR). For digital health innovators and healthcare technology providers, understanding how to integrate effectively with System C is crucial. A key component of this integration is the use of HL7 messaging standards, which form the backbone of data exchange between CareFlow and Trust Integration Engines (TIEs). This article explores how HL7 message types and flows work within CareFlow EPR integration, and what innovators need to know to build reliable, future‑proof solutions.
Health Level Seven (HL7) is an internationally recognised set of standards for the exchange of electronic health information. Within the UK, HL7 underpins interoperability between clinical systems, enabling information such as demographics, appointments, referrals, admissions and results to move securely and accurately between applications. System C’s CareFlow EPR supports HL7 version 2, with specific adoption of HL7 UK A.2 standards and certain enhancements from HL7 2.5. This means digital health innovators must be able to handle HL7 structures to ensure their solutions integrate seamlessly with CareFlow and Trust Integration Engines.
System C’s CareFlow uses the CareFlow Integration Engine (CIE) to manage message exchange with a Trust’s Integration Engine. Connectivity is achieved using TCP/IP sockets with HL7 messages transported via the Minimal Lower Layer Protocol (MLLP). The integration process is designed to ensure data consistency, guaranteed delivery and strict sequencing, which are critical in a healthcare environment where the integrity of patient records is paramount. Messages are queued, persisted, and delivered in a First‑In‑First‑Out sequence, with acknowledgements (ACKs) ensuring confirmation at every stage.
A wide range of HL7 message types are used within CareFlow EPR integration, each designed to manage specific aspects of patient care and operational workflow. For innovators planning integrations, understanding the most common message types is essential.
The MPI lies at the heart of CareFlow integration, ensuring that every patient record is uniquely identifiable across systems. Typical messages include ADT^A28 for creating new patients, ADT^A31 for updating demographics, and ADT^A40 for merging duplicate records. Outbound messages keep third‑party systems up to date, while inbound MPI feeds ensure CareFlow itself receives accurate patient identifiers.
Inpatient workflows rely heavily on ADT messages. These include ADT^A01 for admissions, ADT^A02 for transfers, and ADT^A03 for discharges. There are also variations to handle updates, cancellations and home leave scenarios. By processing these messages, CareFlow and its connected systems maintain a real‑time view of patient movement across wards and departments.
Effective waiting list management is central to patient flow. CareFlow uses ADT^A05 messages for pre‑admissions, ADT^A08 for updates, and ADT^A38 for cancellations or deletions. Outpatient care is managed using a similar structure, with referral messages such as REF^I12 to initiate referrals, REF^I13 to modify, and REF^I14 to cancel or delete referrals. This ensures referrals, appointments, and attendances are accurately tracked across the system.
Clinical diagnostics and laboratory workflows are supported through HL7 order and result messaging. The OMG^O19 and OML^O33 message types handle clinical and laboratory orders respectively, while ORU^R01 and OUL^R22 manage results delivery. These ensure clinicians have timely access to patient test orders, specimen tracking, and diagnostic results, integrated directly into the CareFlow EPR.
For system configuration and maintenance, MFN^M02 and MFN^M05 messages manage updates to staff and practitioner records as well as ward and bed allocations. This ensures organisational structures, healthcare professionals, and resources are correctly aligned within the EPR.
One of the challenges in healthcare integration is ensuring data remains consistent across systems. CareFlow addresses this through a combination of message queuing, acknowledgements and persistent storage. Messages are not discarded until they are confirmed as received and processed by the TIE. In addition, the use of HL7’s null versus empty conventions ensures that updates are handled correctly, preventing accidental data loss or duplication.
For digital health innovators, integrating with System C’s CareFlow presents a significant opportunity to enhance patient care pathways. Whether through patient engagement platforms, decision support tools, or advanced analytics, solutions that can plug into CareFlow via HL7 messaging add value by extending the functionality of the core EPR. However, success depends on a deep understanding of HL7 message structures, mapping requirements, and the nuances of the CareFlow Integration Engine.
Given the complexity of HL7 messaging and the critical role CareFlow plays in NHS Trust operations, many organisations choose to partner with integration specialists. At 6B, our expertise lies in navigating the technical and operational complexities of System C integration, ensuring that new digital solutions work seamlessly within CareFlow ecosystems. We provide support from initial planning through to live deployment, helping innovators accelerate adoption while maintaining compliance and patient safety.
System C’s CareFlow EPR is a cornerstone of modern NHS digital infrastructure, and its ability to communicate through HL7 messaging is fundamental to its success. For digital health innovators, understanding HL7 message types and flows is not just a technical requirement but a strategic advantage. By mastering MPI, ADT, referral, order and result messaging, innovators can ensure their solutions integrate seamlessly, supporting clinicians, administrators, and patients alike. With the right technical approach and strategic partners, System C integration becomes a powerful enabler of digital health innovation in the UK.
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