How to read the RCT registry
A reader's guide to what each randomized-controlled-trial entry shows — and what it does not.
The American Society of Hirudotherapy maintains a registry of randomized controlled trials (RCTs) relevant to medicinal leech therapy. The registry is a research and education resource: it catalogues what each study reported so that clinicians, researchers, and students can appraise the primary literature for themselves. This page explains how to read an entry — and, just as importantly, how not to read one.
A study result is not a protocol
A single RCT — or even several — describes what happened to a specific group of participants, under specific conditions, measured against specific endpoints. That is not a clinical protocol, a treatment recommendation, or a promise of any outcome for any individual. The registry does not tell you what to do for a patient.
Every entry must be read together with its limitations. A positive finding in a small, unblinded trial is a hypothesis to be tested further, not a conclusion to act on. ASH publishes these entries to make the evidence legible, not to endorse any use of leech therapy. Nothing in the registry is medical advice.
What each entry shows
Every registry entry is structured around the same fields so that two trials can be compared on equal footing. Here is what each field means and how to weigh it.
Study design
How the trial was built: randomization method, presence and type of a control or comparator arm, and blinding (open-label, single-blind, or double-blind). Design drives how much confidence a result deserves. A randomized, double-blind, placebo-controlled trial supports a stronger inference than an open-label trial where participants knew their assignment. Note that sham-blinding is difficult with leech therapy, so many entries are open-label by necessity — a limitation, not a flaw to ignore.
Endpoints
What the trial actually measured. The primary endpoint is the outcome the study was designed and powered to detect; secondary endpoints are additional measures that are exploratory by comparison. Distinguish patient-relevant endpoints (pain, function, quality of life) from surrogate or laboratory measures. Beware reading a positive secondary endpoint as if it were the trial's main result — it was not powered for that, and the finding may be due to chance.
Sample size
How many participants were enrolled and analyzed. Small trials are more vulnerable to chance findings, baseline imbalance between arms, and the effect of a few dropouts. A small sample does not make a result wrong, but it widens the uncertainty around any effect estimate. Where the entry reports a confidence interval, read its width, not just whether it crossed the no-effect line.
Limitations
The constraints that bound what the trial can support: short follow-up, single-center enrollment, lack of blinding, selective reporting, attrition, narrow eligibility criteria, or conflicts of interest. The limitations field is not boilerplate — it is the part of the entry that tells you how far the result can travel. Readers are expected to appraise limitations before drawing any conclusion. A result you cannot appraise is a result you cannot rely on.
How an entry's evidence grade fits in
Each entry carries a GRADE-aligned evidence badge. The badge summarizes the strength of the design, but trial design alone does not determine the grade — sample size, blinding, and consistency with other trials all matter. A single RCT can be downgraded for small N or unblinded design. For the full framework, see how ASH grades evidence.
Aggregates multiple RCTs with formal quality assessment. The strongest synthesis of trial evidence in the registry.
Single-trial evidence. May be downgraded for small N, unblinded design, or selection bias — read the limitations field.
Observational design. Suggests an association but does not establish causation.
Single-patient observation. Hypothesis-generating only.
Citation-integrity status
Every cited trial carries a citation-integrity badge that tells you whether its identifier has been checked. This is a transparency feature: it lets you know how much to trust the link between the entry and the paper it claims to cite, before you rely on it.
Verified (PubMed)
The PubMed Identifier has been resolved against PubMed E-utilities and the title matches the claim. You can rely on the identifier pointing to the paper the entry describes. (A parallel DOI ✓ status applies when a DOI, rather than a PMID, has been confirmed.)
Unverified — pending review
The identifier is on file but has not been re-verified since the last citation audit. Treat it as suspect: open the PubMed link and confirm the title matches the claim before relying on the identifier. The state of this cleanup is tracked publicly at the PMID audit status page.
ASH does not silently revise citations. When a fabricated or mismatched identifier is found, the correction is logged in the public changelog rather than quietly overwritten.
Reading an entry responsibly
- Start with the design and the limitations, not the headline result. A result is only as trustworthy as the trial that produced it.
- Read the primary endpoint as the trial's real finding; treat secondary endpoints as exploratory.
- Weigh the sample size and the confidence interval, not just whether a p-value crossed a threshold.
- Check the citation-integrity badge before relying on a cited paper; follow the link and confirm the title for any entry marked unverified.
- Do not convert a result into a protocol. The registry catalogues evidence; it does not recommend, prescribe, or endorse any treatment. Clinical decisions belong to a qualified clinician and an individual patient.
Related pages
RCT Registry
Browse the catalogued randomized controlled trials with their design, endpoints, and citation-integrity status.
Open the registry →How Evidence Is Graded
The Tier A/B/C framework and GRADE-aligned ratings used across every entry.
Read the framework →