MDR Decision Trees Explained for Medical Device Manufacturers

Medical Device Reporting is not just about submitting a form to the FDA. It is about how you investigate, document, and retain evidence of every reported event. 

Under 21 CFR § 803.18, the FDA makes it clear that MDR compliance depends on how well your organization evaluates events within its Quality Management System, not merely whether a report was filed. 

“Risk management activities, including risk analysis and mitigation, are required to be part of a manufacturer’s quality system to support safe and effective devices throughout the product lifecycle.”
— U.S. Food and Drug Administration, Risk Management Activities Within a Quality System  

This guide explains what § 803.18 requires, why Part 820 evaluations are mandatory, and how manufacturers should structure MDR event files to remain inspection-ready in 2026 and beyond. 

What Is § 803.18 and Who It Applies To 

Section 803.18 defines the recordkeeping requirements for Medical Device Reporting. 

If you are a medical device manufacturer, this regulation applies directly to you. 

It governs: 

• How MDR event files are created and maintained 

• How MDR records may be integrated with complaint files 

• What documentation must exist to support each MDR decision 

How MDR Event Files Can Be Maintained 

If you are thinking: “What are the requirements for establishing and maintaining MDR files or records that apply to me?” This section answers exactly that. 

MDR Files Can Be Part of Complaint Files 

The regulation allows flexibility in how MDR records are stored. 

If you are a manufacturer, you may maintain MDR event files as part of your complaint file under Part 820, provided one condition is met. 

The MDR records must be prominently identified as MDR reportable events. 

This distinction matters because FDA investigators must be able to clearly trace: 

• Which complaints triggered MDR evaluations 

• Which records support MDR decisions 

• Which events were determined to be reportable or non reportable 

Blending MDR records into complaint files without clear identification creates compliance risk. 

Why Part 820 Evaluation Is Mandatory for MDR Compliance 

Submitting an MDR report alone does not satisfy § 803.18. 

The FDA explicitly states that an MDR report will not be considered compliant unless the event has been evaluated in accordance with 21 CFR Part 820 quality system requirements. 

This makes your Quality Management System the foundation of MDR compliance. 

What Is 21 CFR Part 820

21 CFR Part 820 is the FDA’s Quality System Regulation. 

It defines how manufacturers must: 

• Handle complaints 

• Investigate nonconformances 

• Identify root causes 

• Implement corrective and preventive actions 

• Maintain traceable records 

When § 803.18 references a Part 820 evaluation, it means MDR events must follow these formal quality workflows. 

What a Part 820 Evaluation Must Include 

A compliant MDR evaluation is not a single step. It is a structured quality process. 

At minimum, this evaluation typically includes: 

Complaint Handling 

The event must be processed using approved complaint handling procedures, including intake, classification, and initial assessment. 

Investigation and Nonconformance Analysis 

The manufacturer must investigate the failure or deviation to determine root cause and contributing factors. 

CAPA Where Required 

If the investigation indicates systemic risk or recurrence potential, corrective and preventive actions must be initiated and tracked. 

Each of these steps must be documented and traceable. 

Documentation Requirements Under § 803.18

Documentation is not optional under this regulation. 

For every MDR event file, manufacturers must maintain: 

1. An explanation if any required information could not be obtained or submitted 
2. The complete results of the Part 820 evaluation for that event 

This documentation demonstrates decision making, not just outcomes. 

During an FDA inspection, investigators expect to see: 

• Why decisions were made 

• How evaluations were performed 

• Whether quality processes were consistently followed 

Incomplete explanations or missing evaluation records are common sources of observations. 

How Manufacturers Decide What Is Reportable and What Is Not 

Medical Device Reporting decisions are rarely obvious at first glance. 

Most compliance gaps do not happen because teams ignore MDR rules. They happen because teams lack a clear, repeatable decision logic for evaluating events consistently under FDA requirements. 

That is where an MDR decision tree becomes essential. 

This guide explains what an MDR decision tree is, how it works, and how manufacturers can use it to make faster, defensible MDR decisions under 21 CFR Part 803 and Part 820. 

What Is an MDR Decision Tree 

An MDR decision tree is a structured evaluation pathway used to determine whether a reported event is MDR reportable. 

It translates regulatory language into a sequence of yes or no questions that guide quality teams through: 

• Event assessment 

• Reportability determination 

• Documentation requirements 

Instead of relying on individual judgment or memory, decision trees enforce consistency. 

Why MDR Decision Trees Matter More in 2026 

Regulatory expectations around MDR have not softened. They have tightened. 

FDA investigators increasingly expect manufacturers to demonstrate: 

• Consistent decision making across similar events 

• Clear rationale for reportable versus non reportable outcomes 

• Traceability between complaints, investigations, MDR decisions, and CAPAs 

Decision trees provide the logic backbone that supports this expectation. 

They also reduce: 

• Delayed MDR submissions 

• Overreporting due to uncertainty 

• Inconsistent decisions across sites or teams 

How an MDR Decision Tree Works 

At its core, an MDR decision tree answers three fundamental questions in sequence. 

Step 1: Is This a Complaint 

The first decision point confirms whether the incoming information meets the definition of a complaint under Part 820. 

“Insert the definition of complaint as per 820”. 

If yes, the event must enter formal complaint handling procedures. 

If no, it must still be documented with justification. 

Step 2: Does the Event Involve a Device Problem or Adverse Outcome 

Next, the evaluation determines whether the event involves: 

• A device malfunction 

• A potential or actual adverse event 

• A situation that could recur and cause harm 

This step prevents premature MDR decisions before investigation. 

Step 3: Does the Event Meet MDR Reportability Criteria 

Finally, the decision tree evaluates whether the event meets MDR reporting thresholds, such as: 

• Death 

• Serious injury 

• A malfunction that could lead to serious harm if it recurred 

Only after this structured evaluation can a defensible MDR decision be made. 

What Makes a Decision Tree FDA Defensible

A compliant MDR decision tree must be embedded in the Quality Management System. 

That means: 

• Every decision node is documented 

• Each answer is supported by investigation results 

• The final determination is traceable to Part 820 evaluations 

A static flowchart without execution and documentation is not sufficient. 

Three Common Examples That Clarify MDR Decisions 

Example 1: Device Malfunction Without Injury 

A device stops functioning during use, but no patient harm occurs. 

The decision tree guides the team to ask: 

• Could this malfunction recur 

• Could recurrence lead to serious injury 

The answer determines reportability, not the absence of immediate harm. 

 

Example 2: Incomplete Information at Intake 

A complaint is received with limited details from the reporter. 

The decision tree documents: 

• What information is missing 

• Why it could not be obtained 

• How the evaluation proceeded despite gaps 

This satisfies § 803.18 documentation expectations. 

 

Example 3: Similar Events Across Multiple Sites 

Multiple complaints appear similar but occur at different facilities. 

The decision tree ensures: 

• Each event is evaluated consistently 

• Trends are detected 

• CAPA initiation is supported by evidence 

Common MDR Decision Tree Mistakes

Many MDR compliance issues do not stem from missing reports. They arise from how MDR decisions are made, documented, and connected to quality processes. 

• Making MDR decisions before investigations are complete 

• Relying on tribal knowledge instead of documented decision logic 

• Treating decision trees as training material rather than live workflows 

• Failing to link MDR decisions to complaint and CAPA records 

These gaps often surface during FDA inspections. 

MDR Decision Tree Checklist 

(Use This to Self-Assess....) 

Before finalizing any MDR decision, confirm that: 

• The event entered formal complaint handling 

• A Part 820 investigation was performed 

• Root cause analysis was completed where applicable 

• CAPA impact was evaluated 

• Missing information was documented with justification 

• The MDR determination is clearly explained 

• All records are traceable and time-stamped 

If any item is missing, the MDR file is not inspection-ready. 

Why Manual MDR Management Breaks Down 

Many organizations struggle with MDR compliance because: 

• Complaint handling and MDR workflows are disconnected 

• Investigations occur outside controlled systems 

• Documentation is fragmented across tools and emails 

• Audit trails are incomplete or reconstructed later 

This increases inspection risk and extends investigation timelines. 

The Advantage of an AI-Enabled QMS for MDR Evaluation 

An AI-enabled Quality Management System directly supports § 803.18 compliance by design. 

When MDR evaluations are executed inside a connected QMS: 

• Every step of the Part 820 evaluation is enforced by workflow 

• Investigation and CAPA activities remain linked to the MDR event 

• Documentation is captured automatically as work is completed 

• Audit trails are complete, time-stamped, and inspection-ready 

Suggestive AI further supports quality teams by guiding users through required steps, reducing missed actions and incomplete records. 

Book A Demo - To see AI-Enabled QMS for MDR Evaluation in Action 

What High-Maturity Manufacturers Do Differently 

Organizations with strong MDR compliance maturity: 

• Treat MDR as a quality process, not a reporting task 

• Evaluate every event through formal QMS workflows 

• Maintain clearly identified MDR event files 

• Rely on automated documentation rather than manual reconstruction 

This approach reduces regulatory risk and shortens investigation cycles. 

What to Do Next 

If your MDR process depends on manual documentation, disconnected tools, or post-event cleanup, it is time to reassess your system readiness. 

A modern, AI-enabled QMS ensures that MDR evaluations under § 803.18 are executed correctly, documented completely, and always inspection-ready. 

See how AI-driven quality workflows can significantly reduce the time and effort required to complete MDR investigations while meeting all Part 820 requirements. 

Book an appointment to explore MDR-ready quality workflows in action.