Conclusion
The disease entity endometriosis is enigmatic and presents a major challenge to developers of potential staging systems. This external validation study demonstrates that the AAGL 2021 endometriosis classification is not generalisable. One of the key strengths of the tool is for high stage disease to distinguish a high level of surgical complexity. While this is of limited utility when endometriosis is diagnosed intraoperatively, these findings suggest that a corresponding pre-operative endometriosis staging system might provide the ability to triage and appropriately plan for the anticipated level of surgical complexity. This finding is consistent with the performance of existing ultrasound-based endometriosis staging tools, particularly with higher stage disease (24). Despite this, survey data suggests that both patients (25) and gynaecologists (26) have limited awareness of non-surgical endometriosis diagnosis.
In the ongoing evolution of endometriosis staging and the search for a universally accepted tool, the AAGL system has some key weaknesses and important strengths. We support the assertion that the ideal staging system should incorporate both a pre-operative and intra-operative arm, predict surgical complexity, correlate well with clinical outcomes relevant to the patient (27) and demonstrate internal and external validity. A prospective external validation of the recently published AAGL system should follow, including a head-to-head comparison with existing and emerging endometriosis staging systems. Standardized surgical data collection would be advisable, as per the Consensus on Recording Deep Endometriosis Surgery statement (28).