Software used in or as a medical device directly influences diagnostic and therapeutic outcomes. Therefore, regulatory authorities such as the U.S. FDA and the European Union (EU MDR 2017/745) mandate that manufacturers demonstrate that software is validated for its intended use, ensuring that it performs consistently, safely, and effectively.
- SIMD (Software in a Medical Device): This can be defined as embedded software that operates as part of a physical device.
- SaMD (Software as a Medical Device): This can be defined as Standalone software that performs a medical function independently of any hardware.
Two Categories: SIMD vs. SaMD
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Aspect
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SIMD – Software in a Medical Device
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SaMD – Software as a Medical Device
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Definition
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Software that is part of a medical device and directly controls or influences its functions.
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Software intended for medical purposes without being part of a hardware medical device.
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Examples
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X-ray acquisition software, ventilator control software, infusion pump firmware.
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AI-based diagnostic apps, ECG interpretation software, cloud-based radiology analysis platforms. |
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Standards
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IEC 62304, IEC 60601-1, IEC 62366-1, ISO 14971
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IEC 62304, IEC 82304-1, ISO 14971
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Validation Focus
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Integration with hardware, real-time performance, safety interlocks.
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Clinical algorithm accuracy, cybersecurity, interoperability, and usability.
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Testing Environment
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Conducted on the integrated device under controlled test setups.
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Conducted in simulated or actual user environments (servers, mobile apps, etc.).
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Software Verification and Validation Report & Plan Template
Full report & plan template for software validation in medical devices.
The Software Validation Life Cycle
Validation is performed throughout the life cycle, not just at the end.
Typical phases include:
1. User Needs & Intended Use DefinitionAt this stage, the manufacturer defines what the software is meant to do and why it exists from a clinical and user perspective. This involves capturing high-level expectations that reflect real-world usage and clinical intent.
Once user needs are defined, they are converted into technical, measurable requirements.
This document is the blueprint that guides design, development, and testing.
This also helps us to define what the software must do to satisfy user needs and comply with applicable standards.
In this phase, the logical and physical structure of the software is created defining how it will meet the requirements. This is also used to design a clear, modular, and testable software architecture that supports safety, maintainability, and scalability.
4. Implementation & Unit VerificationAt this stage, developers translate the design into code. Each software component or module is implemented, verified, and tested individually, also used to ensure that each software module performs correctly and fulfills its design intent before integration.
5. Integration & System TestingAfter all modules are verified individually, they are integrated to test the complete software as a system.
This phase confirms that all components work together as expected and that the software meets overall system requirements it also involves validating interactions between modules, and between software and hardware (for SIMD).
Validation is the most critical phase it ensures the entire software system fulfills its intended use in the real or simulated environment.
While verification confirms that the software was built correctly, validation confirms that the right software was built. This Phase is also used to provide documented evidence that the software satisfies user needs and intended use in actual conditions of use.
After product release, the software enters the maintenance phase — which continues throughout its life cycle. Changes such as bug fixes, performance enhancements, or cybersecurity patches require revalidation to ensure ongoing compliance and safety.
Plays a major role to maintain software in a validated state throughout its lifecycle and ensure that any modification does not impact its intended performance or safety.
Types of Testing in Software Validation
Software validation relies on multiple layers of testing — each designed to address specific risks, requirements, and interfaces.
Below is a detailed breakdown of testing types for both SIMD and SaMD, including their objectives, methodologies
A. Unit Testing
Unit testing is conducted to verify that each individual software unit or component performs its intended function correctly and meets the defined design requirements before integration.
SIMD Focus (Software in a Medical Device)
Unit testing for SIMD targets embedded modules that interact with hardware or perform device-specific control logic. Each module is evaluated independently to confirm accurate output, stability, and error handling under controlled conditions.
Key Aspects:
- Verification of functional modules such as control logic, sensor communication, or image pre-processing.
- Simulation of hardware signals to validate module behavior.
- Testing of boundary conditions, safety interlocks, and exception handling routines.
- Execution of test cases against predefined acceptance criteria from the design specifications.
Example:
In a ventilator system, unit testing verifies that the “Pressure Regulation” module maintains airway pressure within the specified tolerance under simulated patient conditions.
SaMD Focus (Software as a Medical Device)
For SaMD, unit testing focuses on validating algorithmic correctness and data processing logic within independent software modules. It ensures mathematical accuracy, input validation, and predictable performance.
Key Aspects:
- Verification of computational algorithms, statistical methods, or AI inference functions.
- Testing of data validation and error-handling mechanisms for abnormal inputs.
- Use of automated testing frameworks to ensure consistency and reproducibility.
- Evaluation of precision, rounding, and output accuracy for diagnostic computations.
Example:
In a cardiac analysis application, unit testing verifies that the “QRS Detection” module accurately identifies heartbeats and computes heart rate within the required tolerance.
Tools & Methods:
- Static analysis tools, unit testing frameworks.
- Code coverage and boundary value testing.
Expected Outputs:
- Unit Test Plan and Test Case Specifications
- Test Logs and Results (Pass/Fail)
- Defect Reports (if applicable)
- Unit Test Summary Report
B. Integration Testing
Integration Testing is conducted to verify that combined software modules interact correctly, exchange data seamlessly, and function as an integrated unit according to the design architecture.
SIMD Focus (Software in a Medical Device)
Integration testing for SIMD validates the correct interaction between embedded software modules and hardware interfaces. It ensures that communication, timing, and control signals operate reliably within the system environment.
Key Aspects:
- Verification of data and command flow between modules such as detectors, sensors, actuators, and control logic.
- Testing of hardware-software synchronization, interface protocols, and real-time performance.
- Use of hardware simulators or integration benches to replicate actual device behavior.
- Identification of timing or communication errors during concurrent module operation.
Example:
In a patient monitoring system, integration testing confirms that sensor data is accurately acquired, processed, and displayed without delay or data loss.
SaMD Focus (Software as a Medical Device)
Integration testing for SaMD ensures that independent software components—such as algorithms, databases, and user interfaces—interact seamlessly and maintain data integrity across interfaces.
Key Aspects:
- Verification of interoperability between modules via APIs, web services, or middleware.
- Testing of data exchange mechanisms, authentication flows, and error handling during inter-module communication.
- Validation of consistency in data formatting, storage, and retrieval operations.
- Assessment of performance under typical and peak data loads to ensure stable system behavior.
Example:
In a remote diagnostic application, integration testing ensures that patient data processed by the analytical module is accurately transmitted and displayed in the clinician’s dashboard.
Expected Outputs:
- Integration Test Plan and Test Case Specifications
- Test Execution Logs and Communication Trace Records
- Interface Verification Reports and Results
- Defect and Deviation Reports (if any)
- Traceability Matrix (Design Input ↔ Integration Test)
- Integration Test Summary Report
Tools & Methods:
- Hardware-in-loop (HIL) simulations for SIMD.
- API testing tools for SaMD.
C. System Testing
System Testing is very important it’s conducted to validate the software’s complete, end-to-end functionality against defined system requirements, ensuring overall performance, safety, and compliance under realistic operating conditions.
SIMD Focus (Software in a Medical Device)
System testing for SIMD is performed on the fully integrated device, evaluating the interaction of software, hardware, and user interfaces as a complete system. It confirms that the device operates safely and effectively in all intended scenarios.
Key Aspects:
- Verification of all functional workflows, including startup, operation, and shutdown sequences.
- Validation of safety interlocks, alarm handling, and fault recovery mechanisms.
- Assessment of real-time performance, response accuracy, and user interface functionality.
- Execution of scenario-based tests covering both normal and abnormal operating conditions.
- Confirmation of compliance with applicable standards such as IEC 60601-1 and IEC 62304.
Example:
In a dialysis control system, system testing verifies that the software correctly manages fluid flow, pressure, and alarm functions throughout the treatment cycle.
SaMD Focus (Software as a Medical Device)
System testing for SaMD ensures that the complete software application performs as intended in its operational environment—whether on local servers, mobile devices, or cloud platforms. It validates full data flow, usability, and system-level security.
Key Aspects:
- Validation of end-to-end workflow, from data input to result generation and output display.
- Testing across all supported platforms, configurations, and operating systems.
- Verification of data integrity, error handling, and system recovery after failures.
- Evaluation of user interface consistency, performance, and compatibility.
- Confirmation of compliance with IEC 82304-1 and cybersecurity requirements.
Example:
In a telehealth diagnostic platform, system testing verifies that patient data can be uploaded, analyzed, and reported to the clinician accurately and within the defined response time.
Approach:
- Functional testing, boundary testing, and scenario-based validation.
- Verification of alarms, error handling, and recovery sequences.
Expected Outputs:
- System Test Plan and Detailed Test Case Specifications
- Test Execution Records and Functional Test Logs
- Performance and Safety Verification Results
- Non-conformance and Deviation Reports (if any)
- Traceability Matrix (System Requirements ↔ System Tests)
- System Test Summary Report
D. Verification Testing
Verification Testing is conducted to confirm that the software design and implementation accurately fulfill the specified design inputs and technical requirements, providing objective evidence that the product was built correctly in accordance with its specifications.
SIMD Focus (Software in a Medical Device)
Verification testing for SIMD ensures that embedded software components, control logic, and hardware communication functions perform exactly as defined in the design documentation. It validates that all system safety features and performance criteria are met before integration into the clinical environment.
Key Aspects:
- Verification of embedded control logic, communication interfaces, and timing sequences.
- Validation of safety mechanisms such as interlocks, limit checks, and error recovery routines.
- Assessment of compliance with hardware interface specifications and signal protocols.
- Review of traceability between design inputs, code implementation, and test evidence.
- Execution of both automated and manual verification tests against acceptance criteria.
Example:
In a radiation therapy console, verification testing confirms that beam enable signals remain disabled when safety interlocks are active.
Expected Outputs:
- Verification Test Plan and Detailed Test Cases
- Test Execution Records and Logs
- Traceability Matrix (Design Input → Verification Result)
- Verification Test Summary Report
SaMD Focus (Software as a Medical Device)
Verification testing for SaMD confirms that the software design, algorithms, and data flow implementations conform precisely to the functional and performance specifications defined in the SRS and design documents.
Key Aspects:
- Verification of algorithm outputs, data handling logic, and computational accuracy.
- Validation of interface consistency, error-handling procedures, and data exchange mechanisms.
- Review of compliance with design control documentation and risk control measures.
- Execution of verification test cases covering all functional branches and decision paths.
- Assessment of reproducibility and precision of analytical results.
Example:
In a clinical decision support tool, verification testing confirms that the diagnostic score generated by the algorithm matches the accuracy requirement specified in the SRS (e.g., ≥95%).
Output:
Verification report with test cases mapped to each design input, ensuring traceability.
E. Validation Testing
Validation testing is used to demonstrate that the complete software system fulfills its intended use and user needs under actual or simulated use conditions, ensuring the product performs safely, effectively, and as intended in its operational environment.
SIMD Focus (Software in a Medical Device)
Validation testing for SIMD is conducted on the fully assembled medical device, assessing the integrated performance of software, hardware, and user interface in real or simulated clinical environments. It ensures the system performs its intended function reliably and supports safe clinical operation.
Key Aspects:
- Execution of real-world use scenarios replicating clinical workflows and operator interactions.
- Evaluation of usability, functional completeness, and consistency with user needs.
- Verification of safety features, interlocks, and fail-safe responses during actual device use.
- Assessment of compliance with performance and clinical outcome requirements.
- Documentation of user feedback and validation traceability to intended use statements.
Example:
In a patient monitoring device, validation testing confirms that clinicians can continuously monitor and record patient vitals accurately under typical hospital conditions.
Expected Outputs:
- Validation Test Plan and Protocols
- Test Execution Records and User Evaluation Reports
- Validation Summary Report
- Evidence of Traceability to User Needs and Intended Use
SaMD Focus (Software as a Medical Device)
Validation testing for SaMD confirms that the standalone software performs its medical function accurately, consistently, and safely across its intended platforms and user environments. It often includes clinical performance validation using representative or retrospective datasets.
Key Aspects:
- Testing under real or simulated operational conditions using representative user scenarios.
- Clinical validation comparing algorithmic or analytical results against reference standards or expert consensus.
- Evaluation of usability, interoperability, and cybersecurity in deployment environments.
- Verification of data integrity, accuracy, and reliability across all supported configurations.
- Documentation of test results demonstrating conformance with intended clinical performance.
Example:
In a retinal image analysis software, validation testing confirms that the algorithm accurately detects signs of diabetic retinopathy when compared to ophthalmologist-reviewed reference images.
Expected Outputs:
- Validation Test Protocols and Reports
- Clinical Validation Summary (if applicable)
- Usability and Human Factors Evaluation Report
- Final Validation Summary Report
Outcome:
Validation Report demonstrating that user needs, performance claims, and regulatory expectations are met.
F. Regression testing
To ensure that modifications, updates, or bug fixes introduced during maintenance or change control do not adversely affect the existing functionality, performance, or safety of the software.
SIMD Focus (Software in a Medical Device)
Regression testing for SIMD focuses on validating that updates to embedded software—such as firmware revisions, calibration improvements, or minor feature enhancements—do not introduce unintended effects or compromise safety-critical functions.
Key Aspects:
- Re-execution of previously validated test cases after software or firmware changes.
- Verification of hardware-software interaction, communication stability, and interlock functionality.
- Assessment of system responses in both normal and fault conditions to detect side effects.
- Use of automated or semi-automated test scripts for consistent validation across builds.
- Documentation of all test results to demonstrate that unchanged features perform as before.
Example:
In an infusion pump system, regression testing ensures that updates to the flow-rate control algorithm do not affect dose accuracy or alarm behavior.
Expected Outputs:
- Regression Test Plan and Impact Assessment
- Test Execution Logs and Comparative Results
- Defect or Deviation Reports (if any)
- Regression Test Summary Report
SaMD Focus (Software as a Medical Device)
Regression testing for SaMD validates that new releases, algorithm updates, or security patches maintain the integrity, accuracy, and usability of the software across all supported environments.
Key Aspects:
- Identification of impacted modules based on change control documentation.
- Re-testing of core functionalities, data processing, and reporting modules after updates.
- Verification that algorithmic accuracy and clinical performance remain consistent with prior validated versions.
- Execution of automated test suites to compare results across releases.
- Confirmation that integration and interoperability with external systems remain unaffected.
Example:
In a cloud-based diagnostic platform, regression testing confirms that deploying a new security patch does not alter report generation accuracy or data transmission performance.
Expected Outputs:
- Regression Test Protocols and Automated Test Results
- Change Impact Analysis and Traceability Records
- Version Comparison Logs
- Regression Test Summary Report
Tools:
- Automated regression frameworks.
G. Usability (Human Factors) Testing – IEC 62366-1
Usability testing is to confirm that the software interface minimizes the likelihood of use errors and effectively supports intended users in their clinical environment, in alignment with usability engineering principles and IEC 62366-1 requirements.
SIMD Focus (Software in a Medical Device)
Usability testing for SIMD focuses on evaluating how healthcare professionals interact with the device’s embedded software interface. It ensures that operational workflows are intuitive, warnings are clear, and system feedback promotes safe and efficient use.
Key Aspects:
- Assessment of the operator interface, including touchscreen menus, console layouts, and system prompts.
- Evaluation of the clarity and visibility of alarms, notifications, and warning messages.
- Observation of task completion time, error frequency, and user satisfaction during simulated clinical use.
- Validation of system design for workflow efficiency and reduction of cognitive load.
- Documentation of usability issues and associated risk mitigations in the usability engineering file.
Example:
In a patient monitoring system, usability testing ensures that alarm messages are clearly distinguishable and critical warnings are immediately noticeable to clinicians.
Expected Outputs:
- Usability Test Plan and Protocols
- Task Analysis and Observation Records
- User Feedback and Error Logs
- Usability Validation Summary Report
SaMD Focus (Software as a Medical Device)
For SaMD, usability testing evaluates the overall user experience of the software application, focusing on intuitive design, readability, and efficient navigation. It ensures that the interface supports accurate interpretation of results and reduces the risk of user error.
Key Aspects:
- Evaluation of screen layout, terminology, and navigation flow for clarity and consistency.
- Testing with representative end users to assess ease of use, comprehension, and satisfaction.
- Verification that outputs, alerts, and instructions are easily understandable and clinically relevant.
- Assessment of accessibility across different devices (mobile, desktop, tablet).
- Recording of use-related risks and verification of mitigation effectiveness.
Example:
In a clinical data analysis application, usability testing confirms that the report summaries are easily interpretable and that navigation between patient records is seamless.
Expected Outputs:
- Usability Study Protocols and Participant Data
- Observational Notes and Error Metrics
- Human Factors Evaluation Report
- Final Usability Validation Summary
`Outcome:
Human Factors Validation Report including user study feedback and risk mitigation evidence.
H. Performance & Stress Testing
To ensure that the software performs efficiently, remains stable, and sustains its required performance levels under conditions of maximum or prolonged operational load, without degradation in functionality or data integrity.
SIMD Focus (Software in a Medical Device)
Performance and stress testing for SIMD assesses how the integrated software-hardware system behaves under demanding operational scenarios. It ensures that the embedded software maintains responsiveness, reliability, and stability during high workload or extended use.
Key Aspects:
- Evaluation of device performance under continuous operation or rapid workflow transitions.
- Measurement of response times, data throughput, and processing efficiency.
- Assessment of system behavior under prolonged exposure, including temperature or memory stress.
- Verification of error handling and recovery during overload conditions.
- Monitoring of system logs to detect bottlenecks or performance degradation.
Example:
In a computed tomography (CT) system, performance testing confirms that image reconstruction and data storage remain stable during continuous scanning sessions.
Expected Outputs:
- Performance and Stress Test Plan
- Test Execution Records and Response Time Metrics
- System Resource Utilization Logs
- Performance Test Summary Report
SaMD Focus (Software as a Medical Device)
Performance and stress testing for SaMD evaluates the software’s ability to handle high data volumes, concurrent users, or intensive computation tasks, ensuring scalability, reliability, and consistent output accuracy.
Key Aspects:
- Simulation of multiple concurrent users or simultaneous data processing operations.
- Measurement of system response time, processing throughput, and database performance.
- Evaluation of cloud infrastructure behavior under heavy workloads.
- Verification of system stability, crash recovery, and data preservation during peak activity.
- Assessment of performance across different platforms or network conditions.
Example:
In a cloud-based diagnostic platform, stress testing validates that the server maintains acceptable response time and output accuracy when processing large imaging datasets simultaneously from multiple users.
Expected Outputs:
- Performance and Load Test Protocols
- System Metrics and Benchmark Reports
- Error and Stability Logs
- Final Performance Test Summary Report
I. Cybersecurity and Data Integrity Testing
To assess the robustness of the software’s security mechanisms in protecting data confidentiality, integrity, and availability throughout its operation and communication interfaces.
SIMD Focus (Software in a Medical Device)
Cybersecurity testing for SIMD ensures that embedded software and network-connected components are safeguarded against unauthorized access, tampering, or data compromise. It verifies that all communication channels and user access controls meet defined security requirements.
Key Aspects:
- Validation of secure communication interfaces, including DICOM and Ethernet ports.
- Verification of user authentication, role-based access control, and password management.
- Assessment of device behavior when unauthorized connections or data access attempts occur.
- Evaluation of encryption methods for data at rest and in transit.
- Confirmation of logging, alerting, and audit mechanisms for security-related events.
Example:
In a digital mammography system, cybersecurity testing confirms that all USB ports are restricted to authorized devices and that patient images cannot be accessed without authentication.
Expected Outputs:
- Cybersecurity Test Plan and Protocols
- Vulnerability Assessment and Penetration Test Reports
- Access Control and Authentication Test Logs
- Cybersecurity Validation Summary Report
SaMD Focus (Software as a Medical Device)
For SaMD, cybersecurity and data integrity testing focuses on the protection of patient data and system resilience in cloud-based or networked environments. It ensures that encryption, authentication, and secure data exchange mechanisms are effectively implemented and maintained.
Key Aspects:
- Verification of encryption standards (e.g., TLS/SSL) for secure data transmission and storage.
- Assessment of user authentication, session management, and access privileges.
- Execution of penetration testing, static and dynamic vulnerability scans, and OWASP compliance checks.
- Validation of audit trails, data integrity verification, and intrusion detection mechanisms.
- Evaluation of security update management and patch verification processes.
Example:
In a cloud-hosted clinical analytics platform, cybersecurity testing ensures that data transmission between users and servers is encrypted, and the system is resilient against common OWASP vulnerabilities.
Expected Outputs:
- Security and Penetration Test Reports
- Vulnerability Scan Results and Remediation Records
- Data Integrity Verification Logs
- Final Cybersecurity Compliance Report
Is Each Type of Testing is Necessary?
Each testing type serves a distinct purpose in verifying that the software is safe, reliable, and compliant. However, in practice, some tests may be combined or streamlined when their objectives overlap, as long as all functional, performance, and safety requirements are adequately verified.
A risk-based approach should guide the selection of testing activities:
- Critical functions and safety-related features require dedicated and detailed testing.
- Lower-risk or supporting functions may be verified through combined or integrated tests.
- The overall validation must still demonstrate full traceability from requirements to verified results.
Thus, while all testing categories are important, the extent and independence of each test should be determined by risk, software class, and intended use, ensuring efficiency without compromising regulatory compliance or product safety.
Software validation ensures that medical devices — whether embedded systems (SIMD) or standalone diagnostic platforms (SaMD) — deliver their clinical functions safely, effectively, and consistently throughout their lifecycle.
While SIMD validation emphasizes hardware-software integration and operational safety, SaMD validation focuses on clinical algorithm accuracy, cybersecurity, and user interface reliability.
An effective validation strategy demonstrates not only regulatory compliance but also the manufacturer’s commitment to patient safety, quality, and continuous improvement.
In an era where digital health and AI are transforming medical practice, mastering software validation principles is no longer optional — it’s a fundamental competence for every medical device organization.