Alternative Site Testing (AST) Physiology

Alternative Site Testing (AST) allows patients to measure blood glucose from the forearm or palm to reduce pain, as these sites have fewer nerve endings than fingertips. However, AST is limited by physiological lag time. Fingertips have high blood flow and arteriovenous shunts, making their capillary blood closely match arterial glucose levels. In contrast, forearm blood perfusion is slower. During rapid glucose changes (e.g., after eating or insulin injection), forearm results can lag behind systemic levels by 20–45 minutes. This creates a safety risk, particularly during hypoglycemia, where a forearm test might read normal while the patient is actually low. Consequently, AST is enabled by low-volume electrochemical strips (sub-1 $\mu$L) but is clinically restricted to steady-state conditions only.

1 min read

Advanced

2 glossary terms

1 citations

Alternative Site Testing (AST) Physiology

Introduction

Ditch the pain of fingerprick tests! Alternative Site Testing (AST) offers a gentler way to measure blood glucose levels. It uses the forearm or palm instead of fingertips.

Physiology of AST

Fingertips are perfect for accurate readings due to their high concentration of nerve endings and rich blood supply. In contrast, the forearm has fewer nerve endings and slower blood flow.

Limitations of AST

AST has a major limitation: physiological lag time. During rapid glucose changes, forearm results can lag behind by 20-45 minutes. This lag time poses a safety risk, especially during hypoglycemia.

Technology and Innovation

Innovators use low-volume electrochemical strips to make AST possible. However, AST is only safe for steady-state conditions due to the risk of inaccurate readings during rapid glucose changes.

References

FDA Guidance: Blood Glucose Monitoring Test Systems for Prescription Point-of-Care UseSource

Alternative Site Testing (AST) Physiology

Alternative Site Testing (AST) Physiology

Introduction

Physiology of AST

Limitations of AST

Technology and Innovation

References

Was this article helpful?

Related Articles

Environmental Interference Correction

Evolution of Electron Mediators

Wired Enzyme Technology

Capillary Action and Sample Volume Physics

Explore More Topics

History &

Manufacturers &

Research Topics