How to Read an Exosome Certificate of Analysis (COA)

When evaluating an extracellular-vesicle product, you'll often hear the term Certificate of Analysis, or COA.

At first glance, a COA can look intimidating.

It may contain lot numbers, particle concentrations, laboratory methods, sterility results, specifications and terminology that isn't immediately meaningful if you don't work in a laboratory.

But the basic purpose is straightforward:

Learning how to read one can help you move beyond marketing claims and look at the actual information supplied about a product.

What Is a Certificate of Analysis?

A Certificate of Analysis is a quality document associated with a product, material or manufacturing lot.

Depending on the manufacturer and product, it may contain information such as:

• product identification
• lot or batch number
• manufacturing or testing information
• analytical methods
• specifications
• measured results
• particle concentration
• particle-size information
• sterility or microbiological testing
• other quality-control results

Not every COA contains the same tests or uses the same format.

That's important.

A COA isn't valuable simply because a document called a “COA” exists. The useful information is what was actually tested, how it was tested, and what the results show.

Start With the Product and Lot Number

One of the first things to look for is product identification.

A COA should make it possible to determine which product or material the document describes.

Then look for the lot or batch number.

This matters because testing is often performed on material associated with a particular production lot.

If you're evaluating a specific vial or product, a useful question is:

A generic COA from some unrelated batch doesn't provide the same batch-specific information.

That's one reason Express Biologics emphasizes batch-specific COA availability.

Look at What Was Actually Tested

Next, don't simply scan the page looking for words like “passed.”

Look at the tests themselves.

Depending on the EV preparation and the manufacturer's testing program, a COA may report information related to:

Particle concentration

How many detectable particles were measured within a specified volume or sample.

Particle-size distribution

Information about the sizes of particles detected in the preparation.

Characterization

Additional analytical information used to describe the extracellular-vesicle preparation.

Sterility or microbiological testing

Testing intended to evaluate microbial contamination.

Other quality-control measurements

Additional specifications established by the manufacturer for the particular product.

The exact testing panel can vary considerably between products and manufacturers.

Particle Count: Don't Just Look for the Biggest Number

Particle concentration is one of the easiest COA results to notice because the numbers can be enormous.

You might see something expressed as:

which means:

50 billion particles per milliliter.

But as we explain in Understanding Exosome Concentration and Particle Count, a particle number needs context.

Ask:

• Is this concentration or total particle count?
• What volume does the number represent?
• What analytical method produced the measurement?
• Is particle-size information also reported?
• What other characterization was performed?

A larger particle number by itself doesn't automatically tell you that one EV preparation is superior to another.

Particle Count Doesn't Automatically Equal Exosome Count

This distinction is especially important when reading EV documentation.

Some analytical techniques detect particles based on physical properties such as their size, movement or light-scattering behavior.

That does not necessarily mean that every detected particle has individually been demonstrated to be an exosome.

As discussed in Exosomes vs. Extracellular Vesicles: What's the Difference?, “exosome” has a more specific biological meaning than simply “a very small particle.”

Current EV research guidance therefore emphasizes combining multiple characterization approaches rather than relying on one measurement alone. MISEV2023 discusses complementary characterization of EV preparations, including particle concentration, size and EV-associated components.

Look at the Analytical Method

A number becomes much more informative when you know how it was measured.

For particle concentration and size, one technique you may encounter is nanoparticle tracking analysis (NTA).

As we discussed in the previous article, NTA follows the movement of nanoscale particles suspended in liquid and can estimate particle-size distribution and concentration.

Other analytical approaches can also be used for EV characterization.

This matters because different measurement techniques have different capabilities and detection limitations.

So rather than asking only:

“How many particles are there?”

also ask:

“How did the laboratory determine that number?”

That one question provides substantially more context.

Understand the Difference Between a Specification and a Result

COAs may present information in columns such as:

The exact terminology varies, but the underlying idea is important.

A specification describes the manufacturer's established criterion or acceptable range for that test.

A result reports what was measured for the particular lot being documented.

If a result is marked Pass, that generally means it met the applicable acceptance criterion established for that test.

It doesn't mean the word “Pass” independently proves every possible characteristic of the product.

Always look at what test actually passed.

What Does “Characterization” Mean?

Characterization is one of the most important concepts in extracellular-vesicle science.

As explained in How Are Exosomes Produced and Processed?, processing or purification and characterization aren't the same thing.

Processing concerns how material is separated and refined.

Characterization asks:

Researchers can examine characteristics such as:

• particle concentration
• particle-size distribution
• morphology
• EV-associated proteins
• proteins or other components that may indicate non-EV material
• additional physical or biochemical properties

MISEV2023 specifically addresses EV characterization and technique-specific reporting because no single measurement completely describes an extracellular-vesicle preparation.

We'll examine those techniques more closely in Understanding Extracellular Vesicle Characterization and Testing.

What About Sterility Testing?

For biologically derived materials, microbiological quality-control information provides another important category of documentation.

Depending on the manufacturing and testing program, documentation may include testing related to:

• sterility
• aerobic microorganisms
• anaerobic microorganisms
• other microbial or contamination controls

Sterility testing is a distinct quality-control function from EV characterization.

In other words:

Particle analysis asks questions about the particle population.

Microbiological testing asks questions about microbial contamination.

Those are different questions, and both can appear within a broader quality program.

Research examining manufacturing-quality systems for EV preparations likewise treats sterility testing as a distinct quality-control consideration.

What HydroKarma's Documentation Includes

HydroKarma/KWEHEALTH provides batch-specific documentation associated with its products.

According to KWEHEALTH's supplied COA documentation, its quality process includes donor screening and source-material controls as well as testing associated with manufactured lots.

The documentation describes donor screening that includes:

• communicable-disease serology
• medical-history review
• physical examination
• behavioral risk assessment
• additional information relevant to donor suitability

As we explain in How Are Exosomes Produced and Processed?, HydroKarma's process begins with human amniotic fluid rather than collecting extracellular vesicles from cultured-cell-conditioned media.

The supplied documentation also describes manufacturing using aseptic techniques within an ISO-certified controlled environment and quality-assurance/environmental monitoring associated with product lots.

That information provides context about the manufacturer's quality program in addition to the analytical measurements reported for the material itself.

What a COA Can Tell You

A well-documented COA can help answer questions such as:

• Which product and lot does this document describe?
• What tests were performed?
• What methods were used?
• What results were obtained?
• Did the reported results meet the manufacturer's stated specifications?
• What particle concentration or size information was reported?
• What quality-control testing is documented?

Those are useful questions.

But there are also limits.

What a COA Does Not Tell You

A COA shouldn't be treated as a universal scorecard for a product.

For example, a COA doesn't automatically establish:

• that every measured nanoparticle is an exosome
• that the largest particle count represents the best preparation
• that two manufacturers used identical analytical methods
• that two COAs are directly comparable simply because they report similar numbers
• that one analytical measurement completely characterizes an EV preparation

And analytical documentation by itself shouldn't be stretched into conclusions that the testing wasn't designed to establish.

This is why reading the method, units, specifications and results together is much more informative than focusing on a single number.

The Bigger Picture

A COA becomes much easier to understand once you realize it isn't supposed to answer one giant question:

“Is this a good product?”

Instead, it answers a collection of smaller, more useful questions:

• What material was tested?
• Which lot was tested?
• What did the manufacturer or laboratory measure?
• How was it measured?
• What result was obtained?
• What specification was applied?
• What other quality information accompanies the result?

That approach is much more useful than treating a COA as a marketing badge.

The Bottom Line

A Certificate of Analysis provides a window into the testing and documentation associated with a particular product or manufacturing lot.

When reading an extracellular-vesicle COA, pay particular attention to:

And remember that no single measurement tells the entire story.

Particle count can tell you how many detectable particles were measured.

Size measurements can describe the physical distribution of that particle population.

Additional characterization can provide more information about what is present.

Quality-control testing provides another layer of information about the manufactured lot.

The value of a COA isn't simply that it exists. The value is in understanding what the document actually shows.