Surreal illustration of VEGF assay analysis with interference from anti-VEGF molecules.

VEGF Assays Under Scrutiny: Are We Measuring What We Think We Are?

Mira Elwood in Health & Wellness December 2025 • 4 min read.

"Experts question the reliability of VEGF measurements in the presence of anti-VEGF therapies, urging careful interpretation of assay results."

Vascular Endothelial Growth Factor (VEGF) plays a vital role in angiogenesis, the process through which new blood vessels form. Because of its importance in various diseases, including several ocular diseases, accurately measuring VEGF levels is crucial for research and treatment. Many clinical studies use anti-VEGF (anti-Vascular Endothelial Growth Factor) therapies to manage conditions like neovascular age-related macular degeneration (AMD) and diabetic macular edema (DME).

These therapies work by inhibiting VEGF, aiming to reduce abnormal blood vessel growth. Yet, measuring VEGF levels in the presence of anti-VEGF drugs presents challenges. Researchers have raised concerns about the accuracy of common VEGF assays when anti-VEGF therapeutics are also present in the samples, suggesting that these drugs can interfere with the assay results, leading to potential misinterpretations.

This article addresses the issues surrounding VEGF measurements when anti-VEGF therapies are used, delving into the complexities and offering insights to help clarify what these assays actually measure. Understanding these nuances is essential for clinicians and researchers alike, ensuring informed decisions about treatment and further study.

The Central Question: What Do VEGF Assays Really Measure?

Surreal illustration of VEGF assay analysis with interference from anti-VEGF molecules.

The primary concern revolves around what VEGF assays are truly measuring when anti-VEGF therapies are involved. Some assays may only detect the 'free' or unbound VEGF, meaning the VEGF that is not already bound to an anti-VEGF drug. This is important because anti-VEGF molecules, designed to bind and neutralize VEGF, can impact the assay's ability to accurately quantify the total VEGF present.

A key point of contention is that many anti-VEGF molecules don't form complexes solely with ocular VEGF; they can also bind to systemic VEGF. This interaction raises questions about whether the assay is truly reflecting the biologically active VEGF or if it's skewed by the presence of the therapeutic agent.

Free vs. Bound VEGF: Assays may predominantly measure unbound VEGF, potentially underestimating the total VEGF in samples with anti-VEGF drugs.
Interference from Anti-VEGF Drugs: The presence of these drugs can physically block VEGF detection or alter assay dynamics.
Clinical Implications: Misinterpreting VEGF levels could lead to incorrect assessments of treatment efficacy and safety.

In a publication in IOVS, it was highlighted that caution must be taken when interpreting data as anti-VEGF therapeutics interfere with VEGF measurements in samples where both are present. For example, measured VEGF concentrations using the assay kits were lower than calculated theoretical values. The values were determined from the concentration of VEGF and anti-VEGF (known values in their experiments) and literature-derived dissociation constant values.

Moving Forward: Best Practices for VEGF Measurement

Given these concerns, experts recommend a cautious approach to interpreting VEGF assay results in the context of anti-VEGF therapies. Researchers and clinicians should be aware of the limitations of each assay and consider the potential for interference. Ensuring the accuracy of VEGF measurements will not only enhance the reliability of research findings but also improve patient care.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1167/iovs.18-24792, Alternate LINK

Title: Comments On Assays Used To Measure Vegf In The Presence Of Anti-Vegf Therapeutics

Subject: General Medicine

Journal: Investigative Opthalmology & Visual Science

Publisher: Association for Research in Vision and Ophthalmology (ARVO)

Authors: Eric Wakshull, Robert Avery, Mauricio Maia

Published: 2018-08-10

Everything You Need To Know

Why is it important to accurately measure Vascular Endothelial Growth Factor (VEGF) levels?

Accurately measuring Vascular Endothelial Growth Factor (VEGF) levels is crucial because VEGF plays a vital role in angiogenesis, which is the formation of new blood vessels. Given VEGF's involvement in various diseases, particularly ocular diseases, precise measurements are essential for effective research, diagnosis, and treatment of conditions like neovascular age-related macular degeneration (AMD) and diabetic macular edema (DME).

What are the primary concerns regarding Vascular Endothelial Growth Factor (VEGF) assays when anti-VEGF therapies are being used?

The primary concerns revolve around what Vascular Endothelial Growth Factor (VEGF) assays are actually measuring in the presence of anti-VEGF therapies. There are concerns about the accuracy of Vascular Endothelial Growth Factor (VEGF) measurements in the presence of anti-VEGF therapies, suggesting that these drugs can interfere with the assay results, leading to potential misinterpretations. Some assays may only detect 'free' or unbound VEGF, potentially underestimating the total VEGF if anti-VEGF drugs are present. This is further complicated by the fact that anti-VEGF molecules can bind to systemic VEGF, not just ocular VEGF, raising questions about whether the assay truly reflects biologically active VEGF.

How do anti-VEGF drugs interfere with the measurement of Vascular Endothelial Growth Factor (VEGF) in assays?

Anti-VEGF drugs can interfere with Vascular Endothelial Growth Factor (VEGF) measurements in several ways. They can bind to VEGF, forming complexes that some assays may not detect, leading to an underestimation of total VEGF levels. Additionally, the presence of anti-VEGF drugs can physically block the detection of Vascular Endothelial Growth Factor (VEGF) or alter the dynamics of the assay itself. The measured Vascular Endothelial Growth Factor (VEGF) concentrations using the assay kits were lower than calculated theoretical values, indicating interference.

What are the implications of misinterpreting Vascular Endothelial Growth Factor (VEGF) levels when anti-VEGF therapies are in use?

Misinterpreting Vascular Endothelial Growth Factor (VEGF) levels in the presence of anti-VEGF therapies can lead to incorrect assessments of treatment efficacy and safety. If an assay underestimates the total Vascular Endothelial Growth Factor (VEGF) due to interference from anti-VEGF drugs, clinicians may incorrectly adjust treatment plans or misjudge the severity of the condition. This could compromise patient care and affect the outcomes of clinical studies, so caution must be taken when interpreting data as anti-VEGF therapeutics interfere with VEGF measurements in samples where both are present.

What best practices should clinicians and researchers follow to ensure the accuracy of Vascular Endothelial Growth Factor (VEGF) measurements when anti-VEGF therapies are being administered?

To ensure the accuracy of Vascular Endothelial Growth Factor (VEGF) measurements, clinicians and researchers should adopt a cautious approach when interpreting assay results in the context of anti-VEGF therapies. They should be aware of the limitations of each assay and consider the potential for interference from anti-VEGF drugs. It's crucial to understand whether an assay measures free Vascular Endothelial Growth Factor (VEGF), bound VEGF, or total VEGF. Additional steps may be necessary to validate assay results, such as using orthogonal methods or adjusting the assay protocol to minimize interference. Ultimately, ensuring the accuracy of VEGF measurements will enhance the reliability of research findings and improve patient care.