Weekly Blood Spot Testing Shows Promise for Tracking Beta Cell Preservation in Type 1 Diabetes

When Type 1 diabetes is diagnosed, some insulin-producing beta cells often remain and continue working for months or even years. Measuring how well these cells are preserved is crucial for understanding whether new treatments are working. Currently, the gold standard test is a mixed-meal tolerance test (MMTT)—a procedure where patients eat a special meal and doctors measure C-peptide levels (a marker of insulin production) at specific times over two hours. While reliable, this test requires office visits and can be inconvenient for patients.

Researchers have long searched for simpler alternatives that could be done at home or in everyday settings. Two candidates are a urine test and dried blood spot testing, which requires only a small finger prick and can be collected frequently without special equipment.

The USTEKID trial tested whether these simpler methods could replace the traditional MMTT while evaluating ustekinumab, an experimental treatment for newly diagnosed Type 1 diabetes. Researchers collected C-peptide samples using all three methods: traditional mixed-meal tolerance tests at weeks 28 and 52, urine tests after each meal test, and dried blood spots collected weekly for the first six months and then monthly through month 12.

The results showed clear differences in how early each method could detect changes. The urine test did not show meaningful changes in C-peptide levels during the first six months, only declining by month 12. The traditional mixed-meal test showed differences between the treatment and control groups, but only by week 52.

The dried blood spot method, however, detected a difference between the treatment and control groups by week 20—more than four months earlier than the traditional test. The frequent sampling schedule also provided a clear picture of how C-peptide levels were changing over time in both groups.

These findings suggest that dried blood spot testing—when done frequently—may be more sensitive than traditional methods at detecting early signs of beta cell preservation. This sensitivity could help researchers identify whether a treatment is working sooner in the trial process, potentially allowing for faster decision-making about continuing or modifying studies.

The simplicity of dried blood spot collection also opens possibilities for more frequent monitoring without requiring patients to visit clinics repeatedly. Weekly testing via finger pricks at home is considerably less burdensome than repeated mixed-meal tolerance tests.

However, the research team notes that six months of weekly dried blood spot data could predict 12-month results in the control group but not reliably in the group receiving the experimental treatment—suggesting that the method still has limitations and that longer-term data may be needed when a treatment is actively changing beta cell function.

While these results are encouraging, dried blood spot testing is not yet ready to completely replace traditional methods in clinical practice. The findings from USTEKID demonstrate promise, but additional studies will be needed to confirm whether this approach works reliably across different patient populations and different types of interventions.

For now, this research highlights how thoughtful study design—including frequent, simple measurements—can provide clearer and faster insights into whether new treatments are preserving beta cell function in Type 1 diabetes.

Source: Diabetes care. Evidence type: PubMed indexed literature. Type1Cure is an information and intelligence hub, not a medical advice service. This article summarizes published research and does not provide diagnosis, treatment, or personal medical guidance. Always talk to your own care team before changing anything about your Type 1 diabetes management.