Three Questions for Understanding Medical Devices: Purpose of Use, Operating Principle, Performance

Knowing the Product Name is Different from Understanding the Product

"This is a measuring device that uses a sensor."

This description alone makes it difficult to determine what is being measured, who will use the results, and under what conditions performance should be verified.

It is important to look at the listing of functions alongside the situations in which the product is used.

The FDA also guides on verifying whether a product qualifies as a medical device by first organizing its intended use and indications for use.

This is U.S. guidance and does not replace assessments by other countries.

FDA Product Classification Guidance

This article proposes three questions to help understand and explain products, rather than making specific item or classification judgments.

First, What is the Purpose of Use?

The purpose of use is different from a list of functions.

It describes what type of information the product provides or what treatment it is meant for.

In the case of a hypothetical measuring device, one may inquire beyond "it displays a value" to ask:

• What physical condition or quantity is being measured?
• Who uses it, medical professionals or the general public?
• Are the results observational information or do they support a specific judgment?
• What conditions are excluded for the intended target and environment?

Do not arbitrarily expand on aspects that have not yet been confirmed.

It is more important to separate the scope of release from future development.

Second, What Process Produces the Result?

The operating principle cannot be explained by just naming components.

When viewed in sequence from input to output, the roles become clear.

For example, the following structure can be applied:

Signal Acquisition → Signal Processing → Calculation or Transformation → Result Display → Delivery to User

These fixed steps do not apply to all medical devices.

Products that perform functions based on material properties or passive mechanisms require different ways to organize their principles.

Any dependencies on external equipment or software should also be indicated.

It must be clear where the product's own functionality ends to easily explain its impact when the configuration changes.

Third, Under What Conditions is Performance Claimed?

Specifications require not only numerical data but also conditions and grounds for those figures.

Below are review questions regarding a hypothetical measuring device, which are not a specific test criteria or acceptance limits.

Product Description	Additional Questions to Verify
Measurement Range	How is it indicated when it exceeds the range?
Accuracy	What criteria was used for comparison, and under what conditions was it evaluated?
Repeatability	How was the variation in repeated measurements verified?
Response Time	What starting and ending points were based for the measurement?
Operating Environment	Did you review the environmental effects such as temperature, humidity, and movement?

Just displaying more decimal places does not equate to higher accuracy.

The described units and actual measurement performance must be explained separately.

Distinguishing Items When Reading Performance Tables

Describing a product's performance with the single term "precise" can lead to mixing different characteristics.

When reading numbers, first check what they represent.

The following are questions for understanding products and are not common pass criteria.

Item	How to Read	Conditions to Consider
Display Unit	Spacing of numbers presented distinctly on the screen	Rounding, display method
Difference from Criteria	Confirm what was used as reference for result comparison	Reference value, method, evaluation range
Variation in Repeated Measures	Check how much the results vary under the same conditions	Repetition conditions, samples, number of measurements
Differences per User	Check for influences due to operation or installation methods	Training, usage methods, working conditions

Do not jump to conclusions about product defects or user errors when measurement results differ.

It is essential to separate equipment, sample conditions, installation, measurement order, and environment to review the cause of differences.

When performing quantitative statistical evaluations, appropriate methods and conditions must be separately determined based on the purpose.

Placing Product Descriptions and Grounds Side by Side

If one intends to write "measures stably in various environments" in the introduction of a hypothetical measuring device, one must first define what "various environments" means.

If test data only addresses specific indoor conditions, it should not be presented as if confirmed in other environments.

For internal review purposes, the following four columns can be created:

Assertion Phrase → Confirmed Conditions → Supporting Documentation and Version → Unconfirmed Range

For example, the function "automatically saves measurement results" opens up questions regarding the point of saving, guidance in case of saving failures, and the range that can be checked.

Simply stating the existence of the automatic saving function does not imply that all records are preserved without omission.

Checklist Questions for Readers of Medical Device Information

• Which model and configuration does this description pertain to?
• Whom do the results assist in making what type of judgment?
• Can the conditions and limitations of performance figures be identified?
• Do the introduction documents, usage guides, and evaluation materials describe the same scope?
• Is there any expression of unconfirmed details as if they are established performance?

These questions can be utilized both in the purchasing and development phases of the product.

Since each medical device has different operating mechanisms and assessment purposes, it is advisable to avoid directly comparing numbers from different products without conditions.

Connecting the Three Questions in One Sentence

"This product provides performance based on what principle for which user and subject under what conditions and grounds."

If filling in this sentence reveals ambiguous parts, seek answers from development specifications and evaluation materials rather than refining promotional phrases.

Also, confirm that product descriptions, testing plans, and usage guides do not refer to different scopes.

This article discusses the ways to read the principles, components, and performance of medical device categories.

MedQraft organizes the review scope so that product descriptions, permitting, and quality management materials are linked and coherent.