Hypothesis: Afternoon CGM metrics will outperform fasting glucose for early detection of clinically meaningful steroid-induced hyperglycemia during autoimmune flare treatment

Steroid-induced hyperglycemia in autoimmune disease is often missed because many monitoring workflows still prioritize fasting glucose, even though morning prednisone commonly drives post-lunch and late-afternoon dysglycemia.

Hypothesis In adults receiving systemic glucocorticoids for rheumatic or autoimmune flare management, continuous glucose monitoring (CGM)-derived afternoon metrics (for example, 12:00-20:00 mean glucose or time-above-range) will detect clinically meaningful steroid-induced hyperglycemia earlier and with higher sensitivity than fasting glucose alone.

Why this is plausible

• Glucocorticoids increase hepatic gluconeogenesis and peripheral insulin resistance.
• Prednisone-pattern exposure often produces a delayed daily glucose peak, so fasting values can remain misleadingly acceptable.
• Autoimmune flare care frequently involves repeated bursts, tapers, or pulse therapy, magnifying this blind spot.

Testable design

• Prospective multicenter cohort of patients with RA, SLE, vasculitis, PMR, or inflammatory myopathy starting >=20 mg/day prednisone-equivalent or pulse steroids.
• Compare fasting glucose, pre-dinner capillary glucose, and CGM afternoon area-under-curve against a reference definition of clinically important steroid hyperglycemia.
• Primary endpoint: sensitivity for detection within the first 72 hours.
• Secondary endpoints: infection, treatment interruption, rescue insulin, and calibration by baseline HbA1c.

Falsification criteria This hypothesis would be weakened if fasting glucose performs equivalently to afternoon CGM metrics for early detection and outcome prediction after adjustment for baseline diabetes status and steroid dose.

Limitations

• CGM availability may vary by setting.
• Inpatient and outpatient steroid patterns differ.
• Signal may depend on steroid formulation and timing.

References

1. Clore JN, Thurby-Hay L. Glucocorticoid-Induced Hyperglycemia. Endocr Pract. 2009;15(5):469-474. DOI: 10.4158/EP08331.RAR
2. Roberts A, James J, Dhatariya K, et al. Management of hyperglycaemia and steroid (glucocorticoid) therapy. Diabet Med. 2018;35(8):1011-1017. DOI: 10.1111/dme.13675
3. Mertens B, et al. A Practical Guide for the Management of Steroid Induced Hyperglycaemia in the Hospital. J Clin Med. 2021;10(10):2154. DOI: 10.3390/jcm10102154