Response

The summative usability validation referenced in §20 of the CEP was conducted as a standalone human factors validation study in October 2025, in accordance with IEC 62366-1:2015 §5.9 and the FDA Final Guidance on Applying Human Factors and Usability Engineering to Medical Devices (February 2016). The study was not embedded within a specific clinical investigation but was designed as an independent evaluation of the device's user interface for both intended user groups. The CEP (R-TF-015-001) has been updated to reflect the completed status of this evaluation. Red-lined documentation is provided.

The study is fully documented in the following records:

• R-TF-025-004 Summative Evaluation Protocol
• R-TF-025-005 Summative Evaluation Observation Form
• R-TF-025-006 Summative Evaluation Questionnaires (HCP and ITP versions)
• R-TF-025-007 Summative Evaluation Report

Methodology

The study enrolled 36 participants across the two intended user groups: 18 healthcare professionals (HCPs) and 18 IT professionals (ITPs). HCP participants comprised 10 nurses (55.6%), 5 dermatologists (27.8%), and 3 general practitioners (16.7%). ITP participants comprised software engineers, DevOps engineers, backend developers, API integration specialists, and systems integrators. HCP testing was conducted in person at a rented event space in Valencia, Spain, on 22 October 2025. ITP testing was conducted remotely via video conference between 14 and 25 October 2025. To maximise ecological validity, HCP participants used their own personal smartphones to capture images and interact with the device.

Critical tasks were defined in R-TF-025-004 and tested through the following scenarios:

• HCP Scenario 1 (Simulated Use: No Lesion): Participants photographed a skin area with no lesion and interpreted the device output.
• HCP Scenario 2 (Simulated Use: Lesion): Participants photographed a skin lesion and interpreted the device output, including clinical findings.
• HCP Scenario 3 (Knowledge Assessment): Four questions assessing comprehension of report contents, malignancy probability interpretation, detected conditions, and understanding that the device is not intended for diagnosis.
• ITP Scenario 1 (Simulated Use): Seven tasks covering access to the IFU, API authentication, sending and receiving requests, verifying response fields, and checking the API version.
• ITP Knowledge Assessment: Six questions on endpoint URLs, JSON response handling, and error handling procedures.

Results

HCP simulated use scenarios 1 and 2 achieved 100% success (18/18). ITP simulated use achieved 100% success across all 7 tasks (18/18). ITP knowledge assessment achieved 100% success across all 6 questions (18/18). HCP knowledge assessment (Scenario 3) achieved variable results: Q1 94.4%, Q2 100%, Q3 100%, Q4 72.2%. A total of 1 use error, 3 close calls, and 2 use difficulties were observed, all in HCP Scenario 3. No use problems were observed during simulated use or in ITP testing.

System Usability Scale (SUS) scores were 82.5 for HCPs and 85.2 for ITPs, both classified as "Excellent" and exceeding the target threshold of 70 ("Good").

The use problems observed in HCP Scenario 3 (particularly Q4, where 72.2% of participants correctly identified that the device output is not a diagnosis) have been subjected to root cause analysis and residual risk assessment in accordance with R-TF-025-004, §14.7 and EN 62366-1 §5.9. This detailed analysis, including the assessment of associated risks and mitigations, is documented in the updated R-TF-025-007. Red-lined documentation is provided.

The summative evaluation concludes that the device can be used safely and effectively by all intended user groups in the intended use environments.

Relevant commits

• 81dc5d93e (2026-03-08, Taig Mac Carthy): Updated R-TF-015-001 (CEP) §20 Usability Engineering from future tense to past tense, reflecting the completed summative evaluation (October 2025). Documents the rationale for conducting it as a standalone HF validation study rather than embedded in a clinical investigation, and references R-TF-025-004 through R-TF-025-007.