Scientific Validity: The Gate Most IVD Files Never Pass

Written by HATEM RABEH, MD, MSc Ing

Your Clinical Evaluation Expert And Partner

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Scientific validity is the first checkpoint in IVD clinical performance evaluation. It is also the one most manufacturers misunderstand or document poorly.

I have reviewed technical files where analytical performance data spans fifty pages, but scientific validity receives three sentences copied from a reference textbook. The manufacturer assumes it is obvious. The reviewer does not.

This is not a theoretical problem. It is a gating issue. If you cannot demonstrate that your measurand is scientifically established for the intended use, the rest of your clinical evidence becomes irrelevant.

What Scientific Validity Actually Means

Scientific validity is defined in IVDR Annex XIII as the ability of a measurand, biomarker, or test to accurately identify or predict the physiological or pathological condition of interest.

It is not about your device. It is about the biological relationship between what you measure and what you claim to detect, predict, or monitor.

If you develop an assay for a novel cardiac biomarker, you must show that this biomarker correlates with myocardial damage or cardiovascular risk. If you measure glucose in interstitial fluid, you must show that interstitial glucose reflects blood glucose in a clinically meaningful way.

The evidence comes from independent scientific literature, not from your own device data.

Why Reviewers Check This First

The logic is straightforward. If the biological relationship is not scientifically established, then measuring it accurately is meaningless.

You can build a perfectly precise and reproducible assay. If the target you measure has no proven clinical relevance, the device has no clinical value.

I have seen manufacturers invest years optimizing analytical performance for markers that lack sufficient scientific validity evidence. When the file reaches the Notified Body, the question is immediate: where is the proof that this biomarker works?

This is not a documentation problem. It is a strategic misstep. Scientific validity should be confirmed early, before significant development investment.

The Evidence Structure Reviewers Expect

Scientific validity evidence must come from peer-reviewed literature, meta-analyses, consensus statements, or clinical guidelines.

Single studies are rarely sufficient unless the measurand is well-established. Reviewers want convergence across multiple independent sources.

For well-known markers like HbA1c or troponin, scientific validity is straightforward. You reference established clinical guidelines and authoritative reviews. The link between the marker and the condition is documented globally.

For novel or emerging biomarkers, the burden increases significantly.

You need mechanistic studies showing the biological pathway. You need clinical studies demonstrating correlation with the disease state. You need prospective data linking the marker to patient outcomes.

If the marker is very new, you may need to acknowledge that scientific validity is still emerging. This shifts your intended use, your claims, and your risk classification.

MDCG 2022-2 makes this clear: the level of scientific validity evidence required depends on the novelty of the measurand and the clinical context.

What Goes Wrong in Practice

The most common mistake is confusing scientific validity with analytical validity.

Analytical validity proves your device measures the marker accurately. Scientific validity proves the marker itself is clinically meaningful.

Manufacturers demonstrate their assay measures troponin with excellent precision. They assume this proves clinical utility. It does not. They still need to show that elevated troponin indicates myocardial injury and predicts cardiac events.

For established markers, this step feels redundant. But the evidence must still be documented explicitly in the clinical evaluation report.

Another issue is referencing outdated literature or isolated studies.

A single positive study from 1998 does not establish scientific validity in 2025. Reviewers look for current evidence, systematic reviews, and clinical adoption reflected in guidelines.

If subsequent studies contradict the original findings, or if the marker fell out of clinical use, your file has a problem.

When Scientific Validity Is Uncertain

What if your marker is novel and the evidence is limited?

You have two options.

First, you can generate the scientific validity evidence yourself through clinical studies. This is resource-intensive and regulatory complex because you are proving the biology, not just the device.

Second, you can narrow your claims and position the device as investigational or for research use only until the marker gains broader clinical acceptance.

This is not failure. It is regulatory realism.

I have worked with manufacturers who spent two years trying to force a scientific validity argument with insufficient data. The file was rejected repeatedly. When they repositioned the device scope, the path forward became clear.

Regulatory agencies and Notified Bodies will not approve clinical claims based on speculative biology. They require established science.

How This Connects to the Broader Clinical Performance File

Scientific validity is the first element in Annex XIII of the IVDR. It is not isolated.

Once scientific validity is established, you move to analytical performance. Can your device measure the valid marker accurately and reliably?

Then clinical performance. Does your device produce results that match the clinical truth in real-world conditions?

Finally, clinical benefit. Do those results improve patient outcomes or clinical decision-making?

Each step depends on the previous one.

If scientific validity collapses, the entire structure collapses.

This is why reviewers check it first. It is the foundation. If the foundation is weak, nothing built on top will stand.

Practical Steps for Your File

Start by defining your measurand precisely. What are you measuring? What is the biological entity or process?

Then gather independent evidence that this measurand is linked to the condition, disease state, or physiological parameter you claim.

Structure the evidence logically: mechanistic rationale, clinical correlation studies, consensus statements, guideline incorporation.

If the marker is well-established, this section can be concise but must still be explicit.

If the marker is novel, this section becomes a substantial literature review with critical appraisal.

Include a clear statement of scientific validity in your clinical evaluation report. Do not leave it implicit.

Finally, align your intended use and claims with the strength of scientific validity evidence. Do not overclaim.

Why This Matters Beyond Compliance

Scientific validity is not a bureaucratic hurdle. It protects clinical utility and patient safety.

If a marker is not scientifically valid, clinicians may make decisions based on meaningless data. That is a patient risk.

Regulatory requirements force manufacturers to confirm that what they measure actually matters clinically.

This discipline improves device design, sharpens clinical claims, and reduces post-market failures.

When I review a file with strong scientific validity documentation, I know the manufacturer understands their device’s clinical role. When it is weak or missing, I know the project is built on assumptions.

Scientific validity is where clinical thinking begins. It is not paperwork. It is the first real question: does this marker tell us something true about the patient?

If the answer is yes, and you can prove it, the rest of the file has a chance. If the answer is uncertain, stop and resolve it before moving forward.

Next time, we will look at analytical performance—how you prove your device measures that valid marker accurately and reliably. That is where most manufacturers feel more comfortable. But without scientific validity established first, analytical performance evidence is just precise measurement of the irrelevant.