How the Freestyle Libre 3 Could Revolutionize Diabetes Management in Cats: What Veterinarians Need to Know

Managing diabetes in cats can be a complex challenge, particularly when it comes to accurately monitoring blood glucose levels. Traditional methods often involve frequent blood tests, which can be invasive and stressful for both the cat and its owner. Enter the FreeStyle Libre 3 (FSL3) Continuous Glucose Monitoring System—an innovative device that has shown promise in humans but has not yet been fully evaluated for its use in cats. A recent study is changing that by investigating the accuracy of the FSL3 in feline patients, offering veterinarians new insights into how this system could transform diabetes care for cats.

What is the FreeStyle Libre 3?

The FreeStyle Libre 3 (FSL3) is a continuous glucose monitoring system that measures interstitial glucose concentration (IG) rather than directly testing blood glucose. It has gained popularity in human medicine due to its smaller size and increased accuracy compared to previous versions. The system offers real-time glucose readings and eliminates the need for multiple daily blood tests, which is a game-changer for diabetic human patients. But how does it perform in cats?

The Study: Testing FSL3's Accuracy in Cats

The study, conducted by Antonio M. Tardo and colleagues, evaluated the accuracy of the FSL3 in seven healthy, purpose-bred cats with experimentally induced hypoglycemia. The researchers compared the interstitial glucose concentrations measured by the FSL3 with blood glucose concentrations obtained using a more traditional method (AlphaTrak2) during hyperinsulinemic-hypoglycemic clamps.

The primary aim was to assess the accuracy of the FSL3 in detecting glucose levels, especially in hypo- and euglycemic states (low and normal glucose levels, respectively). The study analyzed 474 paired measurements to determine how well the FSL3 performed across different glycemic states.

Results: What We Learned About FSL3's Performance

The results showed that the FSL3 provided strong correlation with blood glucose in stable glycemia (r = 0.86), meaning that when blood glucose levels were steady, the system worked quite well. However, the accuracy was less reliable when blood glucose levels were changing. In these instances, the FSL3 still showed moderate correlation (r = 0.73) but was less precise.

While the system didn’t achieve perfect analytical accuracy, it was clinically accurate—meaning that, in most cases, the device gave readings that were clinically acceptable for veterinary use. The Parkes Error Grid analysis (EGA), a tool used to determine clinical accuracy, showed that 99-100% of the results fell into zones A + B, which are considered clinically safe and acceptable.

A Glycemic-Dependent Bias: What Does it Mean for Cats?

The FSL3 did show some biases depending on the glycemic state of the cat. Specifically, the system tended to underestimate blood glucose in euglycemia (normal glucose levels) and mild hypoglycemia (slightly low glucose levels). For example, in the range of 91-120 mg/dL, the system underestimated blood glucose by -11.7 mg/dL on average. This was also the case for mild hypoglycemia (66-90 mg/dL), where the underestimation averaged -5.5 mg/dL.

However, the system performed differently in more marked hypoglycemia (glucose levels below 55 mg/dL), where it tended to overestimate blood glucose levels. For example, in the range of 46-55 mg/dL, the system overestimated blood glucose by 6.3 mg/dL, and in severe hypoglycemia (below 45 mg/dL), the overestimation was even higher at 15.7 mg/dL.

What Does This Mean for Cats with Diabetes?

While the FSL3 offers a convenient, non-invasive way to monitor glucose levels in cats, veterinarians should be mindful of its glycemic-dependent bias. In practice, this means that the system may underestimate glucose levels when a cat is in a normal or mildly low state, but it overestimates in severe hypoglycemia. For veterinarians, this insight is crucial for ensuring that the FSL3 is used safely, especially in cases where precise glucose control is essential.

Conclusion: A Step Forward for Diabetic Cat Care

Despite the bias issues, the study highlights that the FreeStyle Libre 3 offers an excellent tool for routine glucose monitoring in diabetic cats, particularly for managing hypoglycemia and euglycemia. With its real-time glucose data and ease of use, the system could significantly improve the quality of life for both diabetic cats and their owners. However, as with any diagnostic tool, understanding its limitations is key to using it safely and effectively.

For veterinarians, recognizing the glycemic-dependent bias of the FSL3 will ensure its clinical application remains safe and effective. As the technology continues to improve, it could revolutionize how diabetes is managed in cats, providing a less invasive, more accurate alternative to traditional blood glucose monitoring.