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Patient Merge and Demerge

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Dr M H B Ariyaratne edited this page Jun 4, 2026 · 2 revisions

Patient Merge and De-merge

Overview

When two patient records exist for the same person, a system administrator can merge them into a single record. The merge re-assigns all bills, encounters, investigations, and reports from the secondary (duplicate) record to the primary (surviving) record. The secondary record is then deactivated.

Every merge is fully reversible via the Unmerge function, which restores both records to their exact pre-merge state using a stored JSON snapshot.

The tools are located under Administration → Manage Metadata → Patient Data Management.

Key Concepts

Term Meaning
Primary patient The surviving record — keeps its ID; all history is consolidated here
Secondary patient The duplicate — deactivated after merge; demographics preserved for unmerge
Merge snapshot A JSON copy of both patients' full demographics taken before any change
Affected record Any bill, encounter, investigation, or report re-pointed from secondary to primary
Unmerge Full reversal of a merge — restores the secondary patient and re-points all affected records back

Who Can Merge and Unmerge

Users must hold the Merge Patients (MergePatients) privilege. Grant it via Administration → Manage Users in the relevant role's System Administration privilege group.

Merge Methods

1. Manual Merge

Use when you have already identified two specific duplicate patients.

  1. Open Administration → Manage Metadata → Patient Data Management → Manual Merge
  2. Search for and select the Primary Patient (the record to keep)
  3. Search for and select the Secondary Patient (the duplicate to deactivate)
  4. Review the side-by-side demographics preview
  5. Optionally enter a Merge Reason
  6. Click Merge and confirm the dialog

The system immediately:

  • Saves a JSON snapshot of both patient and person records
  • Re-points all v1-scope records (see table below) from secondary to primary
  • Fills any null fields on the primary from the secondary (never overwrites existing primary data)
  • Sets the secondary patient to inactive with a note recording the merge

2. Deterministic Scan

Automatically finds patient pairs that share an identical NIC, PHN, or MRN. These are near-certain duplicates — data entry error or system import caused two records to be created for the same person.

  1. Open Patient Data Management → Deterministic Scan
  2. Set a Max results cap (default 50, maximum 500)
  3. Click Scan by NIC, Scan by PHN, Scan by MRN, or Scan All
  4. The results table shows each duplicate pair with the matching field highlighted
  5. For each pair:
    • Select which patient is the Primary (default: the older record by creation date)
    • Click Merge to merge, or Dismiss to skip this pair for now

Dismiss hides a pair from the current scan session only — it does not prevent it appearing in a future scan.

3. Probabilistic Scan

Surfaces likely duplicates using fuzzy matching on name, date of birth, and phone number. Suitable for finding duplicates created by spelling variations or transposed digits.

  1. Open Patient Data Management → Probabilistic Scan
  2. Set Max candidate pairs (default 100, maximum 1000) and Name similarity threshold (default 0.92)
  3. Click Run Scan
  4. The results table shows each suggested pair with a match score and breakdown:
Component Method Weight
Full name Jaro-Winkler similarity 40%
Date of birth Exact/near-exact day match 35%
Phone / mobile Last 7–9 digits match across all phone/mobile combinations 25%
  1. For each pair, review the score breakdown, select the primary, and click Merge or Dismiss

Pairs that have already been merged (in any direction, regardless of merge status) are excluded from scan results.

What Is Re-pointed During a Merge

Version 1 scope (current release)

Entity Field moved
Bills patient
Patient Encounters patient
Patient Investigations patient
Patient Reports patient

Future scope (planned, not yet implemented)

The following will be included in a future release:

  • Bill Items, Bill Fees
  • Lab: Patient Samples, Sample Components, Report Groups, Report Item Values, Lab Test History
  • Inward: Patient Rooms, Transfer Requests, Reservations
  • Clinical: Prescriptions, Prescription Templates, Clinical Finding Values, Item Usages
  • Finance: Patient Deposits, Deposit History
  • Administration: Patient Insurance, Patient Flags, Patient Items
  • Family: Family Members, Family records
  • Communications: Tokens, Appointments, SMS, Emails, Notifications, Uploads, Form Values
  • Credit: Encounter Credit Company links
  • Channelling: Patient Session Instance Activities

Demographics — Merge Rules

Situation Outcome
Primary field has a value Primary field is kept; secondary value discarded
Primary field is null, secondary has a value Secondary value is copied to the primary
Both fields are null Remains null

The primary patient's record is never overwritten. The merge only fills gaps.

Multi-level Merges

Multiple merges involving the same patient are fully supported. Each merge is stored as an independent record. For example:

  • Patient C merged into Patient B → one merge record
  • Patient B then merged into Patient A → a second, separate merge record

Unmerging the B→A merge only undoes that specific merge. The C→B merge remains active independently and can be unmerged separately if needed.

Merge History

Administration → Manage Metadata → Patient Data Management → Merge History shows all past merge events.

Filters

  • Date range (from / to)
  • Status: All / Active / Reversed
  • Merged by (user)

Report columns

Column Description
Merge Date When the merge was performed
Merged By Staff member who performed the merge
Primary Patient Surviving patient — name and MRN
Secondary Patient Deactivated patient — name and MRN
Merge Type DETERMINISTIC / PROBABILISTIC / MANUAL
Reason Free-text reason entered at merge time
Affected Records Number of bills/encounters/records re-pointed
Status ACTIVE (green) / REVERSED (grey)
Actions Unmerge button (ACTIVE merges only)

Unmerge (Reversing a Merge)

If a merge was performed in error, it can be fully reversed.

  1. Open Patient Data Management → Merge History
  2. Locate the merge to reverse (status must be ACTIVE)
  3. Click Unmerge
  4. Read the confirmation dialog carefully — it shows the secondary patient name and number of records that will be restored
  5. Click Confirm

The system:

  • Restores each affected record's patient reference back to the secondary patient
  • Restores the secondary patient's demographics from the pre-merge JSON snapshot
  • Re-activates the secondary patient (clears retired flag)
  • Sets the merge record status to REVERSED

Important notes on unmerge

  • Post-merge records are not moved back. Any bill, encounter, or investigation created after the merge date — and therefore pointing to the primary — remains with the primary patient. Only the records that were explicitly re-pointed during the merge are reversed.
  • A reversed merge appears in the history with REVERSED status — it is never deleted from the audit trail.
  • Multi-level merges must be reversed independently — unmerging B→A does not automatically unmerge C→B.

Merge Type Labels

Type Meaning
MANUAL Administrator searched for and selected both patients manually
DETERMINISTIC Merge was triggered from the Deterministic Scan (exact NIC/PHN/MRN match)
PROBABILISTIC Merge was triggered from the Probabilistic Scan (fuzzy match suggestion)

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