Better Blood Tests for Diabetes in Low-Resource Settings

What This Study Found

Researchers tested whether the type of blood collection tube and storage conditions affect the accuracy of insulin and C-peptide measurements. They found that blood collected in EDTA tubes stayed accurate — above 90% of its original level — for up to 24 hours at room temperature. In contrast, plain serum tubes left unprocessed at room temperature caused C-peptide levels to drop to just 51% of the original reading, making those results unreliable.

Why Do Insulin and C-Peptide Tests Matter?

Insulin and C-peptide are two key substances measured in blood to understand how your body handles blood sugar. Doctors use these tests to:

• Determine what type of diabetes you have
• Figure out how much insulin your body is still making on its own
• Guide treatment decisions, such as whether you need insulin injections

These tests are especially important for telling apart Type 1 diabetes (where the body makes little or no insulin) from Type 2 diabetes (where the body still makes some insulin but doesn't use it well).

What Was the Problem Before This Study?

In many parts of the world — particularly in lower-income countries or rural areas — labs are not always nearby. Blood samples often need to be transported long distances to a central lab. Standard guidelines typically require samples to be kept cold and processed (centrifuged) quickly. Without refrigeration equipment or centrifuge machines at every collection point, many patients simply couldn't get these important tests done accurately.

What Did the Researchers Do?

The team drew blood from 10 healthy volunteers and tested different combinations of tube type, storage temperature, and whether the samples were spun in a centrifuge. They tracked how much the insulin and C-peptide levels changed over 24 hours compared to the original baseline reading. A change of more than 10% was considered clinically significant — meaning it could affect medical decisions.

What the Results Showed

The findings were clear:

• EDTA tubes at room temperature, unprocessed: Both insulin and C-peptide stayed above 90% of baseline for the full 24 hours — a reliable result.
• Plain serum tubes at room temperature, unprocessed: C-peptide dropped to just 51% of baseline. This is a dramatic and clinically significant decline.
• Plain serum tubes kept on ice and centrifuged: Results stayed accurate, but this requires equipment many sites don't have.

Why This Matters for Patients

This research is good news for anyone living in an area where access to advanced lab equipment is limited. It means that with the right type of blood tube — an EDTA tube — a blood sample can be collected at a local clinic and safely transported to a central lab within 24 hours without losing accuracy. More patients could receive the correct diabetes diagnosis and the right treatment plan as a result.

Getting the right diagnosis matters. Knowing whether your body still produces insulin can change everything about how your diabetes is managed — from the medications you take to your daily monitoring routine.

A Note on This Study's Limitations

The study included only 8 participants in the final analysis (two were excluded due to sample issues), so it is a small study. All participants were healthy adults, not people with diabetes. Larger studies in real-world clinical settings will help confirm these findings. Still, the results are consistent and clinically meaningful.

Understanding your diabetes type and how much insulin your body produces is a foundation of good diabetes management. If you're looking for trusted diabetes supplies and resources to support your care, visit mdsdiabetes.com to explore our full range of products.

Full Citation

Mubiru, Mukasa, Sekitoleko (2025). EDTA tubes are suitable for insulin and C-peptide measurement in resource-limited settings and can be stored at room temperature for up to 24 hours. PloS One. PMID: 40587435. DOI: 10.1371/journal.pone.0312065