Feasibility of medicinal leech therapy for symptomatic knee osteoarthritis in a US outpatient setting: ASH-Registry pilot study
American Society of Hirudotherapy Clinical Investigators (2024) · Journal of Alternative and Complementary Medicine (preprint) · n=45
Study Profile
- Design
- multicenter (3 ASH-affiliated US clinics), open-label, single-arm prospective cohort with historical control comparison
- Sample size (n)
- 45
- Intervention
- Two sessions of 4-6 Hirudo medicinalis leeches periarticular knee, 28 days apart, performed by FDA-510(k)-trained certified hirudotherapists
- Comparator
- Propensity-matched historical controls from BARI knee OA registry (oral NSAID + topical capsaicin standard care, n=90)
- Primary endpoint
- WOMAC pain at week 12 with safety as co-primary endpoint
- Primary result
- WOMAC pain reduction 47% in leech cohort vs 21% in matched historical controls at week 12 (between-group difference 26%, p<0.001); zero infections, zero major bleeding events
- Effect size (Cohen's d)
- 0.82
- Follow-up duration
- 6 months
Key Findings
- First US-based prospective hirudotherapy study with multicenter design
- Effect size consistent with European RCTs (Cohen's d ≈ 0.82)
- Demonstrated operational feasibility in US outpatient practice under FDA 510(k) K040187 framework
- Zero infections with mandatory ciprofloxacin prophylaxis and Biopharm Leeches Ltd FDA-cleared sourcing
- Patient satisfaction (TSQM-9) very high — 88% would recommend to a friend
Limitations
- Not a true RCT — single-arm with propensity-matched historical controls
- Small sample (n=45)
- ASH-affiliated clinics — selection bias toward CAM-favorable patient population
- Six-month follow-up too short for long-term outcomes
- Pre-print — full peer review pending at time of publication
Clinical Implications
The ASH 2024 US feasibility study is the first US-based prospective evidence for hirudotherapy in knee OA under the FDA 510(k) K040187 clearance framework. The effect size matches European RCTs, supporting the conclusion that the therapy translates to US clinical practice. The study also documents zero infections under standard ciprofloxacin prophylaxis — addressing the most common safety concern raised by US clinicians unfamiliar with the modality. This feasibility study is the foundation for the planned 2026-2028 US multicenter RCT.
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