Class IIa devices sit in the middle of the MDR clinical evidence ladder. Article 61 still requires a clinical evaluation, and Article 61(11) still requires it to be proportionate to the nature, classification, intended purpose and risks of the device — but a Notified Body is now reviewing the clinical evaluation report as part of conformity assessment, and the evidence bar is higher than Class I. For most Class IIa devices, sufficient clinical evidence can be built from a structured literature review, equivalence under MDCG 2020-5, compliance with harmonised standards for the underlying technology, and a PMCF plan that continues to generate data after CE marking. A new clinical investigation is sometimes necessary, but it is not the default. Getting the evidence strategy right is where Class IIa startups either ship on budget or burn a year and several hundred thousand euros on work the Regulation never required.

By Tibor Zechmeister and Felix Lenhard. Last updated 10 April 2026.

TL;DR

  • MDR Article 61(1) requires clinical evaluation for every device. Class IIa is not a quiet middle ground — the Notified Body reviews the clinical evaluation report during conformity assessment.
  • Article 61(11) governs proportionality: the scale of the clinical evaluation and its documentation must match the nature, classification, intended purpose and risks of the device.
  • For Class IIa, the practical evidence hierarchy runs from literature and state of the art, through equivalence under MDCG 2020-5, through harmonised standards for the underlying technology, through a PMCF plan that keeps generating data after CE marking — with a new clinical investigation reserved for the cases where nothing else produces sufficient evidence.
  • PMCF is not optional for Class IIa. Annex XIV Part B applies, and the PMCF plan must be in the technical documentation before CE marking.
  • A Graz-based company we worked with subtracted 2-3 clinical investigations, EUR 400,000-500,000, and 1-1.5 years of timeline by making the evidence argument correctly — the same discipline applies when it is a Class IIa device rather than a Class I.

Why Class IIa is where the evidence strategy either works or explodes

Class IIa is the point where most startups first meet a Notified Body with real authority over their clinical evaluation. Class I self-certified, you wrote the clinical evaluation report and kept it in the technical documentation. Class IIa, the same clinical evaluation report is now being read by an auditor whose signature decides whether you ship. The default reaction — and we see it often — is to panic-scale the evidence work. Commission a clinical investigation "because IIa." Run three literature searches because two felt thin. Write a 180-page clinical evaluation report because the previous one was 60. The budget triples. The timeline stretches. The Regulation never asked for any of it.

The opposite failure is just as common. Founders carry the Class I habit into Class IIa and keep the clinical evaluation report at the same scale they had before. The Notified Body reviewer opens it, sees the gap between the claimed intended purpose and the evidence on the page, and issues a major non-conformity. Now the clinical evaluation has to be redone under review pressure, which is the most expensive way to do it.

Sufficient clinical evidence for Class IIa sits between those two failures. It is more than Class I. It is less than Class III. The Regulation tells you how to find the right level — but only if you read Article 61 the way it is actually written.

What "proportionate" means for Class IIa

Article 61(11) is the clause that makes this possible. It states that the clinical evaluation and its documentation shall be updated throughout the life cycle of the device concerned with clinical data obtained from the implementation of the manufacturer's PMCF plan in accordance with Part B of Annex XIV and the post-market surveillance plan referred to in Article 84, and that the level and type of evidence must be appropriate in view of the characteristics of the device and its intended purpose. That language — appropriate in view of the characteristics of the device and its intended purpose — is the proportionality principle.

For Class IIa the principle lands in a specific place. Class IIa devices are, as a category, medium-risk. They include most non-invasive devices that channel or store body fluids, invasive devices of transient or short-term use, active therapeutic devices intended to administer or exchange energy at low levels, active devices for diagnosis, and a large share of software that falls under Rule 11. The risk profile is real but not extreme. A bad Class IIa device can harm a patient, but the harm is typically recoverable and the mechanisms are usually well-understood from prior clinical experience.

Proportionate for Class IIa means a clinical evaluation that is rigorous enough for a Notified Body reviewer to follow the argument from intended purpose to GSPR coverage without gaps, that is grounded in a defensible literature base or equivalence argument, and that continues to generate data after CE marking through a PMCF plan that actually runs. It does not mean a pre-market clinical investigation by default. It does not mean the same scale of evidence a Class III implant requires. It means a clinical evaluation that matches the specific device in front of you.

The trap is that "proportionate" gets read as "light." It is not. It is "matched." A Class IIa software device that makes diagnostic suggestions in oncology may need substantial clinical data. A Class IIa adhesive with decades of literature behind it may need very little new data beyond a structured literature review. Same class, different evidence bars. The Regulation does not flatten that difference, and the Notified Body will not flatten it either.

The evidence hierarchy for Class IIa

The practical hierarchy of clinical data sources for Class IIa runs the same way it runs for Class I, but the bar at each step is higher.

State-of-the-art and literature review. A Class IIa clinical evaluation starts with a defined literature strategy that establishes the state of the art in the clinical field, benchmarks performance of devices in the same category, and identifies the relevant body of clinical evidence that either covers the device directly or supports the equivalence or literature argument. For Class IIa the literature review must be reproducible — documented search strategy, databases, date ranges, inclusion and exclusion criteria, appraisal methodology, and a traceable path from retrieved literature to the clinical evaluation conclusion. A Notified Body reviewer who cannot re-run the search from the documentation you provided will flag it. Annex XIV Part A specifies the process for clinical evaluation and the content of the clinical evaluation report; the literature pathway must fit that structure.

Equivalence under MDCG 2020-5. Equivalence is available for Class IIa but the bar is not trivial. MDCG 2020-5 (April 2020) requires equivalence to be demonstrated across technical, biological, and clinical characteristics, and the demonstration is evaluated in the round — partial equivalence on one dimension does not carry the argument. For Class IIa the equivalence pathway is genuinely usable when a closely comparable device with accessible clinical data already exists on the market, and the "sufficient level of access to data" question does not block the argument. When equivalence works, it removes the need to generate new clinical data for the aspects already covered by the equivalent device's evidence base. When it does not work, continuing to force it is the most expensive mistake a founder can make at this stage.

Harmonised standards for the underlying technology. Where the device relies on a technology or measurement method covered by a harmonised standard, compliance with that standard provides presumption of conformity with the GSPRs the standard addresses. That presumption reduces — but does not eliminate — the clinical data that has to be generated. This is the mechanism the Graz company used (see below) and it applies identically at Class IIa as it did at their class. The standards register is not only for the physical-safety GSPRs; where a measurement or functional standard is harmonised, its coverage carries into the clinical evaluation argument.

PMCF data as continuing evidence. Class IIa triggers a real PMCF obligation under Annex XIV Part B. The PMCF plan is part of the pre-market technical documentation. After CE marking, the PMCF activities generate new clinical data that updates the clinical evaluation. For Class IIa, a well-designed PMCF is often the mechanism by which the initial clinical evaluation — which may rely heavily on literature and equivalence — becomes stronger over the lifetime of the device. The PMCF is not decoration. It is part of how sufficient clinical evidence is maintained and strengthened after the device reaches the market.

New clinical investigation under EN ISO 14155:2020+A11:2024. For Class IIa a new clinical investigation is sometimes necessary and sometimes not. It is necessary when the literature, equivalence, and standards pathways together cannot produce sufficient evidence for the specific claims being made about the specific device — when, for example, the intended purpose introduces a genuinely new application that existing data does not address. When an investigation is required, EN ISO 14155:2020 (with Amendment A11:2024) is the standard for good clinical practice, and the investigation plan must match what the clinical evaluation needs to fill in, not a generic template.

Equivalence for Class IIa — where it actually works

Equivalence is the most misused pathway for Class IIa devices. The three characteristics MDCG 2020-5 requires — technical, biological, clinical — must all be satisfied, and the evaluation is not a checklist but a reasoned argument that a Notified Body reviewer will challenge. For software that contacts no tissue and contains no substance, biological equivalence is often trivially satisfied, but the technical and clinical dimensions remain non-trivial. For a physical device with patient contact, biological equivalence becomes the hardest piece — different materials, different manufacturing processes, different surface treatments can all break the argument even when the clinical use is identical.

Equivalence works best at Class IIa when the comparator device is from the same manufacturer (so the "sufficient level of access to data" question is answered internally), or when the comparator is a widely-published predicate with a rich independent literature base from which the relevant clinical data can be extracted. Equivalence works worst when the comparator is a competitor device whose clinical data is behind a paywall, inside a technical file you cannot access, or simply not published in enough detail to support the argument.

The honest advice for founders: before committing to an equivalence pathway for a Class IIa clinical evaluation, draft the equivalence table and test it against a skeptical reader. If the technical, biological, and clinical columns all survive, the pathway is real. If any column depends on "we assume" or "probably similar," the Notified Body reviewer will land on the same weak point, and the pathway fails on review. Better to find that out in a two-hour internal review than in a six-month back-and-forth with the NB.

PMCF as continuing evidence — what "lives after CE" means for Class IIa

Annex XIV Part B requires the PMCF plan to describe how post-market clinical follow-up will confirm the safety and performance of the device throughout its expected lifetime, how residual risks identified in the clinical evaluation will be monitored, and how the clinical evaluation will be updated with PMCF data.

For Class IIa, the PMCF plan can take several forms — prospective follow-up studies, retrospective chart reviews, registry participation, user surveys, structured feedback collection from clinical users, literature surveillance for post-market signals, or combinations of all of these. The choice is driven by what the clinical evaluation identified as its weakest evidence points and what the PMCF can realistically strengthen. A PMCF plan that consists only of "monitor complaints and returns" is not a PMCF plan — that is PMS, which is a separate obligation, and conflating the two is a common finding at NB review.

The scale of PMCF for Class IIa is genuinely proportionate. A Class IIa device with decades of literature behind it and no novel claims may have a light, literature-surveillance-centred PMCF. A Class IIa device with a new application of an established technology may need an active PMCF study to close the specific evidence gap that literature and equivalence could not close pre-market. The point is that the PMCF plan is designed — not pulled from a template — and it is designed around the specific evidence gaps the clinical evaluation honestly identified.

A practical example — the Graz pattern applied to Class IIa

A few years ago we worked with a company in Graz building a device that combined two well-established measurement methods in a new way. The innovation was in the combination and the application, not in the underlying physics — the measurement methods themselves had been in clinical use for decades and were covered by recognised harmonised standards.

Their initial clinical strategy was the default one. They had been told to plan 2-3 clinical investigations to generate the clinical evidence for the technical file. The estimate was EUR 400,000-500,000. The timeline was 1 to 1.5 years of investigation work alone, on top of everything else the company had to do. For a startup at their stage, that was the difference between shipping and not shipping.

We ran the Evidence Pass (the third pass of the Subtract to Ship framework for MDR — see post 65). The question it asks is not "what is the cheapest evidence," it is "what does the Regulation actually require, and what is the cheapest legitimate pathway to that requirement?" In this case the answer was sitting in the GSPR chapter and the standards register. The measurement methods were covered by harmonised standards. Compliance with those standards gave presumption of conformity with the relevant GSPRs for the measurement aspects. What remained needing new clinical data was a smaller scope — not the measurement methods themselves, but the specific claims about the combined application.

We documented the argument. We cited the standards. We wrote the clinical evaluation around literature plus the standards-based presumption of conformity plus a targeted PMCF plan for the remaining open questions. The Notified Body reviewed it and accepted the approach. The 2-3 investigations never happened. EUR 400,000-500,000 stayed in the bank. The 1-1.5 years stayed in the runway.

The Graz story is told in this series as a Class I example, but the logic translates directly to Class IIa. The difference is only that for a Class IIa device the Notified Body reviews the clinical evaluation report under conformity assessment, which raises the quality bar for how the argument is written. The same evidence hierarchy — literature, equivalence, harmonised standards, PMCF, investigation as last resort — applies. The same discipline of matching evidence to the specific claim about the specific device applies. The same result is available: real regulatory compliance at a fraction of the default cost, because the default cost assumed work the Regulation never required.

A second practical example — when a Class IIa investigation is the right answer

Not every Class IIa device escapes a clinical investigation, and it is dishonest to pretend otherwise. Consider a Class IIa active therapeutic device that delivers a form of energy in a new anatomical context — the energy modality is established, the safety profile is understood from existing devices, but the specific application is novel and there is no predicate device from which equivalence can be argued. Literature covers the modality but not the application. Harmonised standards cover the electrical and basic safety aspects but not the clinical performance for the new context.

For this device, running the Evidence Pass honestly produces the conclusion that a targeted clinical investigation is necessary — not a three-arm, 500-patient confirmatory trial, but a focused investigation designed under EN ISO 14155:2020+A11:2024 to answer the specific clinical questions the other pathways cannot answer. The investigation is proportionate to the gap. The clinical evaluation report cites literature and standards for everything those sources cover, and the investigation data for the specific claim that only the investigation can support. The combined package is sufficient clinical evidence for the device.

The lesson is not that clinical investigations are always avoidable. The lesson is that they should be run when they are the only honest answer — not as the default, and not at a scale larger than what the specific evidence gap requires.

The Subtract to Ship angle — the Evidence Pass at Class IIa

The Evidence Pass (the third pass in the Subtract to Ship framework for MDR) asks one question before any clinical evidence work begins. What is the cheapest legitimate source of evidence that satisfies the relevant GSPR for this specific claim about this specific device? Work that question through the hierarchy — literature first, equivalence second, harmonised standards third, PMCF as the post-market backbone, and new clinical investigation as the last resort — and the default over-scoping that kills Class IIa projects disappears.

Subtraction at Class IIa means cutting clinical investigations that are not needed, cutting literature searches that go beyond the claims, cutting equivalence arguments that cannot survive a skeptical reader, and cutting PMCF plans that are templates rather than designed activities. It does not mean cutting the clinical evaluation itself. The obligation under Article 61 is absolute. The scale of work to meet it is proportionate. Getting that distinction right is the work.

Reality Check — Where do you stand?

  1. Have you written the intended purpose of your Class IIa device in narrow, specific language that the clinical evidence on your desk actually supports — or are there claims that have no backing data?
  2. Does your clinical evaluation report follow the Annex XIV Part A structure, and can a Notified Body reviewer reproduce your literature search from the documentation as written?
  3. If you are using equivalence, have you tested the technical, biological, and clinical columns against a skeptical internal reader before committing to the pathway?
  4. For every GSPR your device must meet, can you point to the specific source — literature, equivalence, harmonised standard, or investigation data — that demonstrates conformity?
  5. Is your PMCF plan designed around the specific evidence gaps the clinical evaluation identified, or is it a generic template with "monitor complaints" as its substance?
  6. Have you run the Evidence Pass — literature, equivalence, harmonised standards — before concluding that a clinical investigation is required?
  7. If a clinical investigation is required, is it scoped to the specific evidence gap, or has it expanded into a confirmatory trial larger than the Regulation needs?

Frequently Asked Questions

Do Class IIa devices always need a clinical investigation under MDR? No. MDR Article 61 does not mandate clinical investigations for Class IIa as a class. It requires sufficient clinical evidence, proportionate to the device, via a documented clinical evaluation. For many Class IIa devices, literature, equivalence under MDCG 2020-5, and compliance with harmonised standards together produce sufficient evidence without a new investigation. A clinical investigation is required only when the other pathways cannot close the specific evidence gap for the claims being made.

What does "proportionate" mean for Class IIa clinical evaluation? Article 61(11) requires the clinical evaluation and its documentation to match the nature, classification, intended purpose and risks of the device. For Class IIa this means the evidence bar is higher than Class I but lower than Class III, and it is set by the specific device rather than by the class label. A Class IIa device with decades of literature behind it needs less new data than a Class IIa device introducing a novel application of an established technology.

Can a Class IIa clinical evaluation rely on equivalence under MDCG 2020-5? Yes, when equivalence can genuinely be demonstrated across technical, biological, and clinical characteristics as MDCG 2020-5 requires. The equivalence argument must survive a skeptical reading on all three dimensions. Equivalence is most usable at Class IIa when the comparator is from the same manufacturer or has a rich public literature base, and least usable when the comparator device's data is not accessible in enough detail to support the argument.

Is PMCF required for Class IIa devices? Yes. Annex XIV Part B applies at Class IIa, and the PMCF plan must be part of the pre-market technical documentation. The plan must be designed around the specific evidence gaps the clinical evaluation identified, not assembled from a template. A PMCF plan that consists only of complaint monitoring is not PMCF — that is PMS, which is a separate obligation under Article 83 and Annex III.

How does the Notified Body's role change the clinical evaluation at Class IIa versus Class I? For Class I baseline devices, the clinical evaluation is prepared under the manufacturer's own responsibility with no Notified Body review of the clinical evaluation report in the routine conformity assessment. For Class IIa, the Notified Body reviews the clinical evaluation report as part of conformity assessment under the applicable Annex IX or Annex XI procedure. The underlying Article 61 obligation is the same; the quality bar for how the evaluation is written and documented is higher because a trained reviewer will read every page.

Sources

  1. Regulation (EU) 2017/745 of the European Parliament and of the Council of 5 April 2017 on medical devices, Article 61 (clinical evaluation), Article 61(10) (justification where clinical data is not appropriate), Article 61(11) (proportionality and life-cycle update), Annex II (technical documentation), Annex VIII (classification), Annex XIV Part A (clinical evaluation) and Part B (PMCF). Official Journal L 117, 5.5.2017.
  2. MDCG 2020-5 — Clinical Evaluation — Equivalence: A guide for manufacturers and notified bodies, April 2020.
  3. EN ISO 14155:2020 + A11:2024 — Clinical investigation of medical devices for human subjects — Good clinical practice.

This post is part of the Clinical Evaluation & Clinical Investigations series in the Subtract to Ship: MDR blog. Authored by Felix Lenhard and Tibor Zechmeister. Class IIa is where proportionality stops being a slogan and becomes the specific difference between a clinical evaluation that ships and one that burns a year of runway — the Evidence Pass exists to make that difference visible before the invoices do.