Algorithm Change Protocol (ACP) is terminology from FDA’s 2019 proposed AI/ML framework, not the component name in current final guidance. The August 18, 2025 final PCCP guidance, originally issued December 4, 2024, describes three components: Description of Modifications, Modification Protocol, and Impact Assessment. The Modification Protocol covers data management, retraining practices, performance evaluation, and update procedures. Only modifications consistent with the FDA-authorized PCCP may be implemented without an otherwise required new marketing submission. No standard 30-page length is specified.

Why it matters

Common pitfalls

•Treating the ACP as a high-level outline, FDA expects specific protocols with quantitative criteria.
•Omitting subgroup analysis methodology, disparate performance changes across patient subgroups are a focus area.
•Failing to specify rollback procedures, what happens when an update doesn't meet acceptance criteria in production?

Sources

FD&C Act section 515C (21 U.S.C. 360e-4), PCCPs · U.S. Code
MDCG Software Guidance · MDCG
FDA - Software as a Medical Device (SaMD) · FDA

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MedTech terminology is full of pairs that look interchangeable but carry very different regulatory, clinical, and commercial consequences. Picking the wrong framework, pathway, or standard early in a project can add months to a submission, invalidate clinical evidence, or trigger an audit finding. Side-by-side comparison is the fastest way to surface those differences before they become costly mistakes.

Each comparison on this page pulls from the same vendor-neutral, sourced definitions used throughout the MedTech Terms glossary. You see the one-line summary, the formal definition, why it matters in practice, common pitfalls, and the primary sources (FDA guidance, EU MDR/IVDR articles, ISO/IEC standards, MDCG documents, IMDRF principles) that back each entry. That makes the comparison defensible in regulatory strategy memos, design reviews, and submission narratives.

Common comparison patterns

Regulatory pathway choice - 510(k) vs PMA, 510(k) vs De Novo, Abbreviated vs Special 510(k).
Quality systems - QSR vs ISO 13485, QMSR vs QSR.
Software classification - SaMD vs SiMD, Locked vs adaptive AI.
EU frameworks - MDR vs IVDR, CE Mark vs UKCA.
Cybersecurity artifacts - SPDX vs CycloneDX SBOM, CVE vs CVSS.
Post-market actions - Recall vs field action, Removal vs correction.

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MedTech Terms is a vendor-neutral community resource sponsored by Blue Goat Cyber. Definitions are written for educational use and are not legal or regulatory advice.