# Site Fragmentation & Token Site Metric

In clinical research architecture, does the ratio of trial sites to enrolled participants reveal structural differences between African and European research models? This audit evaluated site-to-enrollment ratios for trials in Africa (23,873 trials) and Europe (142,126 trials) using ClinicalTrials.gov API v2 design and location metadata. Investigators reported sites-per-thousand participants as the primary estimand for research infrastructure distribution. African trials average approximately 1.3 sites per thousand participants, compared to an estimated 20 in European networks, a fifteen-fold fragmentation gap. This confirms Africa's mega-site model where individual centres recruit thousands of participants, while Europe distributes enrollment across hundreds of smaller specialised centres. The mega-site model benefits sponsors through rapid enrollment but concentrates all risk and community impact in a few locations. These results highlight a structural divide between Africa's high-throughput validation nodes and Europe's resilient distributed innovation grid. Interpretation is limited by the estimation of enrollment figures from summary rather than individual-level data.

## References

1. Drain PK, et al. "Global migration of clinical trials." Nat Rev Drug Discov. 2018;17:765-766.
2. Siegfried N, et al. "Where does all the money go?" Cochrane Database Syst Rev. 2022.

## Note Block

- Type: research
- App: https://mahmood726-cyber.github.io/africa-e156-students/geographic-equity/dashboards/site-fragmentation.html
- Code: https://github.com/mahmood726-cyber/africa-e156-students/blob/master/geographic-equity/code/site-fragmentation.py
- Data: ClinicalTrials.gov API v2
- Date: 2026-04-05