How ASH grades evidence
The Tier A/B/C framework and GRADE-aligned ratings used across every page.
Every condition, RCT, compound, and biographical entry on hirudotherapysociety.org carries a regulatory-status badge (the colored tag near the page title) and, where applicable, an evidence-quality rating. This page explains what those badges mean.
The three-tier framework
ASH classifies every clinical use of medicinal leech therapy into one of three tiers:
FDA-cleared
The FDA has cleared Hirudo medicinalis as a medical device (K040187, June 21 2004) for venous congestion in surgical flaps. This is the only formally cleared indication. Tier A entries can refer to this clearance without off-label disclaimers.
Example: Venous Congestion in Surgical Flaps, Digit Replantation, Ear Replantation.
Off-label with clinical evidence
Uses outside the FDA-cleared indication that have at least one randomized controlled trial (RCT) or systematic review supporting clinical efficacy. Includes off-label disclaimer language and individualized informed-consent expectation.
Example: Knee Osteoarthritis (multiple RCTs), Chronic Venous Insufficiency, Lateral Epicondylitis.
Investigational
Mechanistic rationale and limited human evidence (case series, small pilots, or preclinical extrapolation). Tier C entries include explicit framing that hirudotherapy is investigational for this use, with patient-discussion expectations covering evidence limits.
Example: Fibromyalgia, Vitiligo, Chronic Tinnitus, Stroke Rehabilitation.
Preclinical / Mechanistic
Pages describing biology, biochemistry, mechanism-of-action research, or omics discovery science. Not a clinical efficacy claim. Common in /science/*, /leech-biology/*, and /research/genome*.
GRADE-aligned evidence ratings
On RCT pages, the evidence-quality badge follows the GRADE Working Group framework. Trial design alone doesn't determine grade — size, blinding, and consistency all matter.
Sources from FDA 510(k) submission file. Top tier for regulatory framing.
Aggregates multiple RCTs with quality assessment. Used for top-of-page recommendations.
Single-trial evidence. May be downgraded for small N, unblinded design, or selection bias.
Observational design. Suggests effect but does not establish causation.
Single-patient observation. Hypothesis-generating only.
In-vivo animal model. Suggests biological plausibility, not human efficacy.
Cell-culture or cell-free assay. Mechanism-of-action evidence only.
Biochemistry, structural biology, computational modeling. Pre-clinical context.
Pre-modern medical literature. Educational reference, not current clinical guidance.
Practice guideline or scope-of-practice statement from a professional society.
Editorial integrity
- PMID verification: Every PMID cited is verified to resolve to a real PubMed paper with title matching the claim. Three fabricated PMIDs were caught and corrected in May 2026 — documented in the public changelog.
- "What this does NOT mean" required: Every Tier B/C condition page carries an explicit
WhatThisDoesNotMeanBoxclarifying evidence limits in patient language. - FDA framing fixed-baseline: Every Tier A page references the exact device clearance (K040187, NRN, Unclassified Pre-Amendment). No inflated claims.
- Drug-vs-leech distinction: FDA-approved drugs derived from leech (bivalirudin, lepirudin, desirudin) are NOT the same as whole-leech therapy. Pages describing the drugs carry explicit separation.
- Public corrections queue: Errata are logged in the changelog, not silently revised. All commit history is on public GitHub.