Design review obligations from ISO 13485 §7.3.5 and the principle of verifying design outputs at each lifecycle phase.
Explicit cross-document verification requirement: detailed design must be confirmed to implement and not contradict the architecture. [Class C] A1:2015 extended to SaMD.
A distinct detailed design review record (not the architecture review) with documented traceability or inspection confirming architectural consistency.
Maps to
IEC 62304: §5.4.4 Verify detailed design
ISO 13485: §7.3.5 Design and development review
Pre-QMSR Part 820 (legacy QSR): §820.30(f) Design verification.
Requirement text
The manufacturer shall verify and document that the software detailed design: (a) implements the software architecture; and (b) is free from contradiction with the software architecture. [Class C]
Why this clause exists
Detailed design verification is the checkpoint that prevents design drift — the phenomenon where detailed design decisions gradually diverge from the architecture during the design process, producing an implementation that is internally consistent but does not realize the architectural intent. For Class C software, architectural decisions are typically made to meet safety requirements (risk control segregation, processing boundaries, fail-safe behavior); if the detailed design contradicts those decisions, the safety intent may be lost even though both the architecture and the detailed design are individually coherent documents. Clause 5.4.4 is a Class C-only requirement because the traceability cost of formal detailed design verification is proportionate to the safety consequence of design drift at that classification level. IEC 62304 NOTE: a traceability analysis of architecture to software detailed design is an acceptable means of satisfying requirement (a).
What changed
Clause 5.4.4 was present in IEC 62304:2006 and retained in A1:2015. The Class C restriction and the two verification requirements (implements architecture; free from contradiction) are unchanged. The A1:2015 amendment expanded scope to SaMD and health software, increasing the Class C population subject to this requirement.
Common gaps (what we see in audits)
- Detailed design verification not performed separately from architecture review — The architecture review doubles as the detailed design review, with no distinct review record for the detailed design phase. Clause 5.4.4 requires verification of the detailed design against the architecture — a review conducted before the detailed design existed cannot satisfy this requirement.
- Verification confirms detailed design exists but not architectural consistency — The design review record confirms that a detailed design document was produced but does not verify that it is consistent with and implements the architecture. The clause requires both existence and architectural consistency — a completeness check alone is insufficient.