Clinical evaluation under MDR is the ongoing, lifecycle process of generating, collecting, analysing, and assessing the clinical data pertaining to a device, defined in Article 2(44) and governed by Article 61 and Annex XIV. A clinical investigation is a specific, formal study involving one or more human subjects, defined in Article 2(45) and governed by Articles 62 to 82 and Annex XV of Regulation (EU) 2017/745, executed under EN ISO 14155:2020+A11:2024. Every MDR device needs a clinical evaluation. Not every device needs a clinical investigation. Conflating the two is the single most expensive conceptual error a MedTech founder can make.

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

TL;DR

  • Clinical evaluation is the broad, continuous process. Clinical investigation is a specific human-subject study. One is a lifecycle activity; the other is a discrete project with a protocol, ethics approval, and a sponsor.
  • MDR Article 61 and Annex XIV Part A govern clinical evaluation. MDR Articles 62 to 82 and Annex XV, together with EN ISO 14155:2020+A11:2024, govern clinical investigations.
  • Every medical device on the EU market needs a clinical evaluation under Article 61. A clinical investigation is only one possible data source feeding that evaluation.
  • For implantable and Class III devices, clinical investigations are required as a general rule under Article 61(4), with narrow exemptions in Article 61(5) and (6).
  • Founders who conflate the two routinely commit to six-figure study budgets that the Regulation never required in the first place.
  • The Annex XIV Part B post-market clinical follow-up (PMCF) process sometimes uses clinical investigations after CE marking, which is where the two concepts legitimately overlap.

Why this distinction matters before you write a single protocol

There is a specific moment in almost every MedTech startup conversation where the whole project can tip in the wrong direction. A founder reads the word "clinical" in the MDR for the first time, reaches for the nearest contract research organisation, and starts budgeting a study. Three months later, the runway has a hole in it and the clinical evaluation plan has not been written.

The mistake is not the intention to take clinical evidence seriously. The mistake is treating "clinical evaluation" and "clinical investigation" as synonyms. They are not. They belong to two different articles of the MDR, two different annexes, and two entirely different scopes of work. Mixing them up is how a startup ends up running a EUR 400,000 study that its Notified Body never asked for, while the clinical evaluation report that was actually required sits unwritten in a drawer.

This post is the definitional reference. If you remember nothing else from the Cat 3 cluster, remember the distinction on this page. Everything else in the clinical evidence workstream is downstream of it.

What clinical evaluation actually means under MDR

MDR Article 2(44) defines clinical evaluation as "a systematic and planned process to continuously generate, collect, analyse and assess the clinical data pertaining to a device in order to verify the safety and performance, including clinical benefits, of the device when used as intended by the manufacturer."

Three words in that definition carry the weight.

Systematic and planned. Clinical evaluation is not an ad hoc collection of whatever studies happen to exist. It is a structured process driven by a clinical evaluation plan (CEP) that pre-specifies the scope, data sources, appraisal criteria, and analysis methods. Annex XIV Part A paragraph 1 sets out the required content.

Continuously. Clinical evaluation does not end when CE marking is granted. It runs for the full lifecycle of the device, fed by PMCF data under Annex XIV Part B, by complaint handling, by new literature, and by updated scientific knowledge. A clinical evaluation report (CER) that is written once and filed away is already out of date.

Clinical data pertaining to a device. The scope is all clinical data relevant to the device and its intended purpose, whatever the source. Literature on the underlying technology, experience with an equivalent device, data from a clinical investigation on the device itself — all of it flows into the same process.

Governing provisions: MDR Article 61 (the core clinical evaluation article), Annex XIV Part A (the structured process and CER content), Annex XIV Part B (PMCF, which feeds the next evaluation cycle).

What clinical investigation actually means under MDR

MDR Article 2(45) defines a clinical investigation as "any systematic investigation involving one or more human subjects, undertaken to assess the safety or performance of a device." Four elements of that definition matter.

Systematic. A written plan, pre-specified endpoints, a defined statistical approach, controlled execution. Informal use of the device on a few willing subjects is not a clinical investigation — it is unauthorised clinical use.

One or more human subjects. Bench testing, simulated-use testing, and animal studies are not clinical investigations. The moment a human subject is enrolled for the purpose of generating safety or performance data on the device, the Article 62 framework applies.

To assess the safety or performance of a device. The purpose of the study is regulatory-grade evidence about the device itself.

The device is the subject of the study. The investigation is centred on the device's own performance or safety profile.

Governing provisions: MDR Article 62 (general requirements), Articles 63 to 82 (informed consent, sponsor obligations, authorisation, adverse event reporting, end-of-investigation reporting, and related procedures), Annex XV (content of the clinical investigation plan, investigator's brochure, device documentation, and reporting), and the harmonised Good Clinical Practice standard EN ISO 14155:2020+A11:2024.

A startup does not get to scale any of this down because it is small. A two-person company running a 20-subject investigation has the same sponsor obligations as a multinational running a 2,000-subject multi-centre Class III trial.

What each one contains

Two different beasts, two different document sets.

A clinical evaluation contains a clinical evaluation plan (CEP) specifying scope, intended purpose referencing Article 2(12), claims to be substantiated, data sources, and appraisal methodology; a structured literature search and appraisal; where applicable, an equivalence assessment under MDCG 2020-5; where applicable, the results of clinical investigations on the device itself; an analysis and conclusions section linked to the general safety and performance requirements of Annex I; and a clinical evaluation report (CER) that is updated throughout the lifecycle of the device based on PMCF data collected under Annex XIV Part B.

A clinical investigation contains a clinical investigation plan (CIP) built to Annex XV requirements; an investigator's brochure; device documentation; ethics committee approval from each member state where the study runs; competent authority notification or authorisation depending on the class and purpose; informed consent documentation under Article 63; site contracts and monitoring plans; adverse event reporting procedures under Article 80; an end-of-investigation report under Article 77; and data archiving in line with EN ISO 14155:2020+A11:2024.

The CER is a document. The clinical investigation is a project with its own documents, people, sites, timelines, budget, and liabilities.

When each one is required

Clinical evaluation is required for every single medical device on the EU market. There are no exemptions. Article 61(1) obliges the manufacturer to confirm conformity with the relevant general safety and performance requirements under the conditions of normal use, to evaluate undesirable side-effects, and to assess the acceptability of the benefit-risk ratio, based on clinical data providing sufficient clinical evidence. A Class I device needs a clinical evaluation. A Class III implantable needs one too. What changes with the risk class is the scope and depth of the evaluation, not whether it is done.

Clinical investigation is required for implantable devices and Class III devices as a general rule under Article 61(4), with specific exemptions defined in Article 61(5) and (6). For devices that are neither implantable nor Class III, a new clinical investigation is not automatically required; the clinical evaluation can often be built from literature, equivalence, and harmonised standards without a new human-subject study, provided the evidence is sufficient for the claims in the intended purpose. Our pillar posts What Is Clinical Evaluation Under MDR? and What Is a Clinical Investigation Under MDR? walk through each side in depth.

The practical consequence: every founder has to write a clinical evaluation. Only some founders have to run a clinical investigation. The ones who confuse the two often end up doing both — the investigation they did not need, and the evaluation they still owe.

How they relate: the investigation feeds the evaluation

The relationship between the two is hierarchical. Clinical evaluation is the container. Clinical investigation is, at most, one of the things that goes into the container.

Annex XIV Part A describes the clinical evaluation process in terms of three legitimate data sources: scientific literature, clinical data from an equivalent device, and clinical data from clinical investigations on the device itself. When a clinical investigation under Article 62 and Annex XV produces results, those results are appraised and analysed inside the clinical evaluation process, alongside the literature and equivalence data, and the conclusions feed the CER.

A clinical investigation is never a standalone deliverable under MDR. Its only purpose is to generate data that the clinical evaluation needs. A study that is run without a clear hypothesis tied to a specific claim in the intended purpose — and a specific gap in the clinical evidence that the literature and equivalence routes cannot close — is a study that will struggle to earn its place in the CER, no matter how much it cost.

When a clinical investigation feeds a clinical evaluation

There are three clean moments where the two genuinely intersect.

Pre-market, when the device is implantable or Class III and no exemption under Article 61(5) or (6) applies. The general rule of Article 61(4) triggers. The clinical investigation is designed, authorised, and executed to generate the pivotal evidence for the CER before CE marking.

Pre-market, for any device where literature and equivalence cannot answer the specific clinical question. Even for lower-risk devices, there are situations where the only honest source of evidence is a targeted investigation on the device itself. The investigation is scoped to the specific gap and nothing more.

Post-market, as part of PMCF under Annex XIV Part B. PMCF can include post-market clinical investigations when the PMCF plan calls for them — for example, to confirm long-term performance, to investigate a signal from vigilance data, or to gather data on specific subgroups. PMCF investigations are still clinical investigations under Article 2(45) and still subject to the Article 62 framework and EN ISO 14155:2020+A11:2024. They are not a lighter regulatory category.

In all three cases, the investigation exists to feed the evaluation. The evaluation is the thing that actually demonstrates conformity. The investigation is one of the ways it does so.

Common confusions to retire before they cost you money

"We need a clinical trial" used as shorthand for "we need clinical evidence." Clinical evidence is the broad Article 61 requirement. A clinical investigation is one way to produce some of it. Treating the two as equivalent is how six-figure study budgets get approved before the clinical evaluation plan has been written.

"The CER is the clinical investigation report." No. The clinical evaluation report is the Annex XIV Part A output document summarising the entire evaluation process across all data sources. The clinical investigation report is the Article 77 end-of-investigation document describing a single study. Two different documents, two different purposes.

"We can skip the clinical evaluation if we run an investigation." The opposite of true. If you run an investigation, the clinical evaluation still has to be done; the investigation results just become one of its inputs. The evaluation is the obligation. The investigation is one possible contribution.

"A Class I device does not need clinical evaluation." Wrong. Every device needs a clinical evaluation. The scope and the depth scale with risk class and novelty, but the obligation itself does not disappear at Class I.

"Equivalence avoids clinical evaluation." Equivalence is a data source inside the clinical evaluation, not a replacement for it. The evaluation process, the CEP, and the CER still exist. What changes is where the clinical data comes from.

"We will do the clinical investigation first and write the CER later." The investigation results have to be appraised and analysed inside the clinical evaluation framework set by the CEP. If the CEP did not exist before the investigation was designed, the appraisal criteria were not pre-specified, and the CER will struggle at Notified Body review.

The practical impact for founders

The practical takeaway is about sequencing and budget control.

Sequence the clinical evaluation plan before anything else in the clinical workstream. The CEP is the cheapest document in the entire MDR project, and it determines whether the most expensive activities — clinical investigations — are actually needed, and if so, what question they need to answer. A founder who writes the CEP first and the study protocol second will spend a fraction of what a founder who does it the other way around spends.

Budget the clinical evaluation and the clinical investigation as separate line items. They are different work, with different people, different timelines, and different risk profiles. Rolling them into a single "clinical budget" hides the place where the Evidence Pass discipline produces its biggest savings: the decision about whether to run an investigation at all.

Talk to the Notified Body about the clinical evaluation strategy before you commission a study. The Notified Body's view on whether literature and equivalence can carry the clinical evaluation is the most valuable piece of information you can get before spending money. Some will push back on literature-only routes even when they are technically defensible; some will accept them readily. Find out which situation you are in before the protocol is written.

The Subtract to Ship angle: keep the words separate, keep the work separate

The Subtract to Ship Evidence Pass starts with a definitional discipline: say clinical evaluation when you mean the process, and say clinical investigation when you mean the study. Never use one word to mean the other. The moment the vocabulary blurs, the scope blurs, and the budget blurs with it. Our methodology pillar The Subtract to Ship Framework for MDR Compliance covers the Evidence Pass in full.

The pass then runs in a specific order. First, write the clinical evaluation plan with the intended purpose tightly defined. Second, identify which general safety and performance requirements actually need clinical evidence. Third, for each one, evaluate literature, then equivalence, then clinical investigation in that order. Fourth, only design a clinical investigation for the gaps the first two sources cannot close — and scope each investigation to the single question it exists to answer, nothing more.

This is not a trick for avoiding required work. When the Regulation requires an investigation, the investigation happens and it is done properly under Article 62, Annex XV, and EN ISO 14155:2020+A11:2024. The Evidence Pass is the discipline of not running an investigation when the Regulation does not require one, and of not confusing the container with one of its possible contents.

Reality Check — Where do you stand?

  1. Can you write, in one sentence each, what clinical evaluation and clinical investigation mean under MDR, without using the other term in either definition?
  2. Have you written a clinical evaluation plan (CEP) under Annex XIV Part A, or are you already designing a study without one?
  3. Do you know which MDR articles govern each concept — Article 61 and Annex XIV for evaluation, Articles 62 to 82 and Annex XV for investigations — and can you look them up without hesitation?
  4. If your device is not implantable and not Class III, have you honestly evaluated whether a clinical investigation is required at all, or is it assumed?
  5. If your device is implantable or Class III, do you know under which paragraph of Article 61(4) to (6) your situation falls?
  6. Have you budgeted the clinical evaluation work and any clinical investigation work as separate line items, so the subtraction discipline has something to work on?
  7. For any clinical investigation on the project plan, can you state in one sentence which specific gap in the clinical evidence it exists to close?
  8. Does your team use the two terms interchangeably in conversation, or has the vocabulary been locked in?

Frequently Asked Questions

What is the difference between clinical evaluation and clinical investigation under MDR? Clinical evaluation, defined in MDR Article 2(44), is the systematic and planned lifecycle process of generating, collecting, analysing, and assessing clinical data pertaining to a device to verify its safety, performance, and clinical benefits. It is governed by Article 61 and Annex XIV. Clinical investigation, defined in MDR Article 2(45), is a specific systematic study involving human subjects undertaken to assess the safety or performance of a device. It is governed by Articles 62 to 82 and Annex XV and executed under EN ISO 14155:2020+A11:2024. Clinical evaluation is the broad process; clinical investigation is one possible source of data that feeds it.

Does every medical device need a clinical evaluation under MDR? Yes. MDR Article 61 applies to every medical device placed on the EU market, without exemption. The scope and depth of the evaluation scale with risk class and novelty, but the obligation to perform a clinical evaluation itself does not disappear for any class of device, including Class I.

Does every medical device need a clinical investigation under MDR? No. Clinical investigations are required as a general rule for implantable and Class III devices under MDR Article 61(4), with specific exemptions in Article 61(5) and (6). For devices that are neither implantable nor Class III, a new clinical investigation is not automatically required; the clinical evaluation can often be built from literature, equivalence, and recognised standards.

Can the clinical evaluation report and the clinical investigation report be the same document? No. The CER is the Annex XIV Part A output summarising the full evaluation process across all data sources. The clinical investigation report is the Article 77 end-of-investigation document describing one specific study. The investigation report feeds into the CER as one of its inputs, but the two are distinct deliverables with distinct scopes.

Which one comes first — the clinical evaluation plan or the clinical investigation plan? The clinical evaluation plan comes first. The CEP defines the intended purpose, the claims to be substantiated, the data sources to be used, and the gaps that each source is expected to fill. Only once the CEP exists does it become clear whether a clinical investigation is required, and if so, what question it must answer. Designing a clinical investigation plan before the CEP exists is backwards and routinely produces studies that do not earn their place in the CER.

Is post-market clinical follow-up (PMCF) a clinical evaluation or a clinical investigation? PMCF, governed by Annex XIV Part B, is part of the ongoing clinical evaluation process. PMCF can include post-market clinical investigations when the PMCF plan calls for them, in which case those investigations are still subject to the Article 62 framework and EN ISO 14155:2020+A11:2024. PMCF itself is the evaluation activity; any PMCF study is an investigation feeding that activity.

Sources

  1. Regulation (EU) 2017/745 of the European Parliament and of the Council of 5 April 2017 on medical devices, Article 2(44) (definition of clinical evaluation), Article 2(45) (definition of clinical investigation), Article 61 (clinical evaluation), Articles 62 to 82 (clinical investigations), Annex XIV Part A (clinical evaluation), Annex XIV Part B (post-market clinical follow-up), Annex XV (clinical investigations). Official Journal L 117, 5.5.2017.
  2. 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 cluster in the Subtract to Ship: MDR blog. Authored by Felix Lenhard and Tibor Zechmeister. The distinction between clinical evaluation and clinical investigation is the first piece of vocabulary a founder has to lock in before the clinical workstream starts — because once the words blur, the budgets blur with them, and the Regulation does not care which one you meant.