Behind the Science: A Patient’s Guide to the AAGL 2021 Endometriosis Classification Study
For years, the conversation around endometriosis severity has been dominated by the outdated ASRM “staging” system (I-IV). As many patients know all too well, this system often fails to capture the reality of their experience, especially when their pain level doesn’t match their assigned “stage.”
At ESSI, we believe in empowering our community with knowledge. That’s why we’re taking a deep dive directly into the landmark 2021 study that created the new AAGL Endometriosis Classification System. Understanding the science behind this new system is key to advocating for better care.
Why Was a New System Needed?
The primary authors of the study, led by Dr. Mauricio S. Abrao, noted that the old ASRM system had critical flaws. It was designed to predict fertility outcomes, not surgical difficulty. This meant that a small but deeply infiltrating lesion on the rectum could receive a similar score to a large but superficial lesion on the peritoneum, even though the surgeries required are worlds apart in complexity.
According to the study, this lack of a reliable surgical complexity score has complicated everything from surgical planning to equitable insurance reimbursement for the time and skill required in complex cases. The goal was to create a new, user-friendly system based on anatomy that could reliably correlate with surgical complexity.
How the AAGL Score Was Built on Expert Consensus
To build a system rooted in reality, the AAGL task force began by surveying 31 internationally recognized endometriosis specialists. These experts were asked to rate the surgical complexity of removing endometriosis from a wide range of specific anatomical sites—the bladder, rectum, ovaries, ureters, and more.
The average “difficulty score” for each location became the foundation of the new points-based system. This means, for the first time, the points assigned to a lesion directly reflect the real-world surgical skill and effort required to remove it, as determined by a consensus of world-leading surgeons.
What the Landmark Study Found
To validate their new system, the researchers prospectively applied it to 1,224 patients with histologically-proven endometriosis across three specialized centers in Brazil and Spain. They compared the new AAGL score against the actual complexity of the surgery performed.
The results were clear:
- High Correlation with Surgical Complexity: The AAGL score proved to be a reliable and reproducible tool for discriminating between four levels of surgical difficulty. The old ASRM score, when applied to the same patients, showed poor reproducibility.
- Correlation with Symptoms: The study found that a higher AAGL stage was significantly associated with more severe dysmenorrhea (painful periods), dyschezia (painful bowel movements), and a higher rate of infertility.
However, the authors honestly and correctly note that the new system’s correlation with pain symptoms was only comparable to the old ASRM system. It did not strongly correlate with non-cyclic pelvic pain. This confirms a crucial point: no classification system based on surgical findings alone can perfectly predict a patient’s unique pain experience.
What This Means For You, the Patient
The AAGL 2021 Endometriosis Classification system is a massive step forward. It provides a more accurate and objective language for your surgeon to describe the anatomical burden of your disease and the true complexity of the procedure required to treat it. This can aid in surgical planning, referrals to specialty centers, and fighting for appropriate insurance coverage.
While it correlates with certain pain symptoms better than the old system, it is fundamentally a surgical complexity score, not a pain score. The conclusion from the science is the same conclusion we hold at ESSI: your story, your symptoms, and your quality of life are, and always will be, the most important metrics in your care.
