Method

How every figure on this site was produced, and what it can and cannot support.

The registry pull returned 192 interventional studies

The trial list comes from the ClinicalTrials.gov API version 2, pulled on 18 September 2026.

A study is included when it is registered as an interventional study and any one of its condition strings contains "essential tremor" or "tremor, essential", matched without regard to case. That filter returned 192 studies. 92 of them are completed.

A trial counts as having results posted to the registry when its record carries a results section. 35 of the 92 completed trials do. The other 57 are the trials carried into the literature search.

The twelve month window leaves 51 trials in the counts

Results take time to write up, so a trial that finished recently is not treated like one that finished years ago.

Each of the 57 trials is marked according to whether twelve months have passed between its recorded completion date and the data date. 51 trials are past that window and 6 are not, either because they finished within the last twelve months or because the registry records no completion date. Every headline count refers to the 51.

The search runs in two stages, and the second runs only when the first finds nothing

Stage A looks for the registration number. Stage B looks for the trial itself.

Stage A: search by registration number

1. PubMed, using the NCT number in the secondary source identifier field, written as the number followed by [si].
2. PubMed again, using the bare number as a free text term, which catches papers that print it in the abstract or the methods without indexing it.
3. Europe PMC, using the bare number, which indexes the full text of open access articles.

Stage B: search by trial specifics

Where no registration number was found, the trial was searched on its own particulars, taken from the registry record.

1. PubMed, by principal investigator surname combined with tremor, restricted to the completion year and the six years after it.
2. Europe PMC, by the intervention combined with the phrase "essential tremor", narrowed by the affiliation of a participating site.

Every hit returned by either stage was opened and read. Nothing was classified on a title alone.

The matching rule

A paper is recorded as the results publication for a trial only when at least three of these four criteria agree with the registry record.

1. The intervention.
2. The study design, including randomisation, blinding and control.
3. The sample size, within 25 per cent of the registered enrolment.
4. A participating site or a named investigator.

Where the registration number appears in the paper, the match basis is recorded as NCT ID match. Where the link rests on the criteria above alone, it is recorded as a specifics match, and the row says so.

Every trial ends in one of four outcomes

Each trial gets exactly one outcome, and the four are defined on the glossary page.

Results publication located: 30 trials, 1,178 participants

A paper reporting the trial’s results was found and met the matching rule. The reference is linked in the table.

Cited in literature only: 6 trials, 422 participants

The trial is referred to in the literature, for example in a review or another trial’s discussion, but no paper reporting its own results was found. The citing reference is linked so a reader can judge it.

No results publication located: 10 trials, 338 participants

Both stages of the search were run and no paper met the matching rule.

Uncertain: 5 trials, 44 participants

A candidate paper exists but the evidence is too thin to tie it to this registry record, for example where the registry entry covers a whole programme. The candidate is linked and the reasoning is in the data file.

What the method cannot support

These limits sit beside the counts on the tracker page as well, because they qualify them.

• No results publication located means the search above did not find one. It does not establish that results were never published. A paper can sit in a journal neither database indexes, or in a language or format the queries did not reach.
• Rows matched on specifics rather than on the registration number rest on agreement of design, site and sample size. That is a judgement, not an identity, and those rows are labelled so a reader can weigh them differently.
• Rows marked uncertain are uncertain. They are neither located nor not located, and they are reported as their own group rather than folded into either.
• The registry record is taken as given. 11 of the 192 registered studies carry no enrolment figure, so participant totals are sums over the trials that report one.
• Results posted to a registry and results published in a journal are different things. A trial can do either, both or neither, and the two are counted separately here.
• The searches were run on 18 September 2026. A paper appearing after that date is not reflected until the next update.
• This is a literature linkage audit, not a determination of anyone’s legal or regulatory reporting duty. Which trials fall under a given reporting requirement is a separate question this site does not address.

Updates and corrections are public

The dataset is refreshed on a weekly cycle and every change is recorded in a dated changelog in the repository.

If you know of a paper this search missed, the corrections page explains how to report it.