Industries like medical devices, in vitro diagnostics (IVDs), pharmaceuticals, and biotechnology develop products that directly impact human health and safety. Given the high level of risk, these industries must follow structured and well-documented development processes that ensure product safety, efficacy, and regulatory compliance.
Two of the most common methodologies used in product development are the Waterfall model and the Agile methodology. Each has distinct strengths and weaknesses, especially when applied in regulated environments. In this article, we explore how these methodologies apply to the medical and IVD sectors—and how a hybrid approach is often the most practical path forward.
Waterfall Model: Structured and Sequential
The Waterfall model follows a linear and sequential flow of activities where progress is made step by step. It’s especially well-suited for regulated product development where traceability, documentation, and formal reviews are essential.
| Phase | Description | Key Elements & Examples |
|---|---|---|
| User Needs | Understand what the end user (e.g., clinician, patient, lab technician) expects from the product. |
- Gathered via interviews, surveys, observations - Documented as high-level needs (e.g., "portable", "fast results") |
| Design Inputs | Convert user needs into detailed, testable, and measurable engineering requirements. |
- Functional specs (what it does) - Performance criteria (speed, accuracy) - Regulatory standards (ISO 13485, IEC 60601) - Risk controls (linked to ISO 14971) |
| Design Process | Actual development stage involving architecture, prototyping, and engineering. |
- Includes software and hardware design - Uses tools like CAD, PCB layout, UML, HMI designs - Iterative refinement of design |
| Design Outputs | Tangible results of the design process that are ready for testing and manufacturing. |
- Drawings, BOMs, source code, software builds - Labeling and Instructions for Use (IFU) - Must be documented in the Design History File (DHF) |
| Design Verification | Ensure that the design outputs correctly implement the design inputs. |
- Bench testing, simulations, software testing - Use of IEC 62304 (software) or IEC 61010 (safety) - Requires test protocols, results, traceability matrix |
| Design Validation | Confirm that the final product meets the actual needs of the users in real-world scenarios. |
- Simulated or clinical use environment - Usability testing per IEC 62366 - May involve clinical trials or pilot studies |
| Design Reviews | Formal, structured evaluations of each phase to ensure design completeness and risk control. |
- Conducted at major project milestones - Includes RA, QA, Clinical, Engineering, etc. - Ensures alignment with regulatory and quality expectations |
Regulatory Fit:
- Aligns perfectly with ISO 13485 design control clauses.
- Supports FDA premarket submissions (510(k), PMA).
- Easier to audit and manage with tools like DHF, DMR, and Trace Matrix.
Limitations:
- Inflexible once in execution—iterating mid-process may mean restarting verification/validation.
- Long timelines before feedback is gathered from actual users.
- Risks becoming "document-heavy" and stalling innovation.
Agile Model: Iterative and Flexible
Agile is a modern, iterative development model that enables flexibility and rapid prototyping. Work is divided into short cycles called sprints, with each sprint delivering a potentially usable piece of the product. While originally used in software, it’s increasingly adapted for hardware-software co-development in medtech, especially in SaMD (Software as a Medical Device) and IVDs.
- Product Backlog & User Stories
- Requirements written as User Stories
(e.g., “As a lab tech, I want to upload results easily…”).
- Prioritized backlog based on value, risk, and
regulatory needs.
- Sprint Planning
- Define sprint goals (2–4 weeks).
- Select backlog items for development and assign
tasks.
- Design & Development (Per Sprint)
- Code, hardware sketches, UI/UX prototypes
created collaboratively.
- Continuous integration (CI) ensures rapid builds
and testing.
- Emphasis on cross-functional involvement (QA/RA,
clinical, marketing).
- Verification & Testing (Within Sprints)
- Each feature is tested before sprint ends (unit,
integration, automated tests).
- Some tests may serve dual purposes: engineering + design verification.
- Sprint Review / Demonstration
- Team presents working increment to stakeholders
for review.
- Retrospective & Process Improvement
- Discuss what went well, what didn’t, and how to
improve next sprint.
- Release / Continuous Delivery
- Working software (or prototypes) can be deployed for stakeholder feedback or early validation activities.
Regulatory Fit:
- Supports early risk mitigation, frequent usability testing, and real-world feedback.
- Requires supporting infrastructure for traceability (e.g., JIRA, Azure DevOps + Polarion/Greenlight Guru).
- Must explicitly document:
- Requirements → design → verification/validation → risk controls
- Document versions, design review sign-offs
- Regulatory deliverables embedded in sprints (e.g., Sprint 5 = Verification Sprint)
- Without discipline, documentation may lag behind.
- Not intuitive for regulators unless structured with compliant templates.
- High dependency on tools to maintain traceability and audit-readiness.
The Hybrid Approach: Best of Both Worlds
The Hybrid model combines the traceability and control of Waterfall with the responsiveness of Agile. Most modern medtech companies use this model, especially when dealing with both software and hardware components.
How It Works:
- Waterfall for Planning: Use a traditional, structured approach for the high-level stages—user needs, design inputs, risk management planning, and regulatory documentation. This creates a robust foundation that meets compliance expectations.
- Agile for Execution: Within the execution phase, use Agile sprints to rapidly prototype, develop, test, and refine product components. This allows responsiveness to feedback without compromising regulatory structure.
- Design Controls Embedded in Agile: Incorporate regulatory artifacts—such as traceability matrices, risk assessments, and validation protocols—within Agile workflows using appropriate software tools.
| Phase | Waterfall Elements | Agile Elements |
|---|---|---|
| Planning | Define user needs, risk assessments, regulatory strategy, standards mapping | Product vision, high-level epics, MVP definition |
| Design Inputs | Formalize engineering specs & test criteria | Create Agile epics & user stories from inputs |
| Development | Structured milestones for design outputs | Sprint-based execution for rapid prototyping |
| Verification | Waterfall-like test protocols for formal verification | Continuous testing during sprints |
| Validation | Final usability & clinical studies | Early user feedback via prototypes |
- Use Agile for R&D and Waterfall for Regulatory Packaging
- Document traceability in sprint deliverables
- Plan design reviews at both the sprint and phase level
- Apply risk-based approach to documentation depth
- Use tools that support hybrid workflows (e.g., code repo + eQMS + design control software)
| Model | Best For | Key Challenges | Compliance Strategy |
|---|---|---|---|
| Waterfall | Hardware-dominant, high-risk devices | Slow iteration, late testing | Robust planning, documentation templates |
| Agile | Software/UX-centric, low-mod risk SaMD | Traceability, doc management | Integrate eQMS tools, maintain trace matrix |
| Hybrid | Mixed systems (e.g., IVDs, connected devices) | Coordination overhead | SOP alignment, formal sprint gates |
Choosing the right product development methodology isn’t about picking sides—it’s about aligning your process with both regulatory obligations and product innovation goals. Waterfall offers structure and predictability, Agile offers speed and adaptability, and the Hybrid approach offers the regulatory safety net with the flexibility to innovate.
Best For: Hardware-dominant, high-risk devices where formal approvals and documentation are critical.
Challenges: Linear structure limits flexibility. Testing comes late in the cycle, leading to potential delays.
Compliance Strategy: Use planning templates, detailed design reviews, and early regulatory involvement.
- ✔ Great for pacemakers, infusion pumps, ventilators
- ๐ Heavy documentation load
- ๐ Predictable, but rigid
Best For: Software-heavy or UX-focused medical apps like SaMD, mobile platforms, or diagnostic dashboards.
Challenges: Maintaining traceability and documentation pace with development sprints can be tough.
Compliance Strategy: Pair Agile tools (Jira, Trello) with eQMS and trace matrix to stay audit-ready.
- ๐ Fast iterations, early feedback loops
- ๐จ๐ป Ideal for AI/ML or health-monitoring apps
- ๐ Continuous verification approach
Best For: Mixed systems like IVDs, smart diagnostics, or devices with both software and hardware components.
Challenges: Coordination and version control across teams using both Agile and Waterfall workflows.
Compliance Strategy: Use formal sprint gates, align SOPs across departments, and maintain unified DHF structure.
- ⚖ Balance speed with control
- ๐ Ensures integrated documentation
- ๐งฌ Great for connected devices & combo products
