> For the complete documentation index, see [llms.txt](https://docs.nested-knowledge.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.nested-knowledge.com/guides/write-a-search-query/clinicaltrials.gov.md).
# ClinicalTrials.gov
Learn how to write a ClinicalTrials.gov search query.
ClinicalTrials.gov is a registry of clinical trials. This includes trials still underway, trials that never resulted in a publication, or trial-level design and outcome data reported directly by the sponsor. It's a companion to your published-literature searches (PubMed, EuropePMC, Embase).
You can search ClinicalTrials.gov in Nested Knowledge two ways: write a query directly, or copy one you've already built on the ClinicalTrials.gov website. Both are covered below.
### Write A Query
Use AND, OR, and NOT with keywords to narrow in on trials of interest. For example:
```
dizziness AND NOT exhaustion AND stroke
```
retrieves trials with "dizziness" and "stroke" anywhere in the record — title, description, interventions, conditions, or other indexed fields — while excluding any trial that mentions "exhaustion." Use parentheses once your logic has more than one or two operators, and quotation marks around any keyword that contains spaces.
#### Search Specific Fields With AREA
To search a specific part of the record rather than the whole trial, add `AREA[AreaName]` before your term:
```
AREA[ConditionSearch]dizziness AND NOT AREA[ConditionSearch]exhaustion AND AREA[ConditionSearch]stroke
```
restricts that same search to trials where these terms appear specifically as studied Conditions. Common area names:
* **BasicSearch** — the default when no area is specified; searches all common fields
* **ConditionSearch** — indexed conditions, condition MeSH terms, title, and keywords
* **InterventionSearch** — indexed interventions, intervention MeSH terms, arm labels, keywords, and more
* **OutcomeSearch** — all registered outcome fields (Primary, Secondary, Other)
* **TitleSearch** — trial name and acronym
Combine areas across a single query:
```
AREA[ConditionSearch]stroke AND AREA[InterventionSearch]Trevo AND AREA[OutcomeSearch]mortality
```
finds trials studying mortality in stroke patients treated with the Trevo device. ClinicalTrials.gov's [full list of AREAs](https://www.clinicaltrials.gov/data-api/about-api/search-areas) covers more specialized fields, like DesignAllocation or OverallStatus, useful for narrower protocols:
```
AREA[DesignAllocation]Randomized AND AREA[OverallStatus]Completed AND AREA[InterventionSearch]Trevo
```
#### Other Operators
Beyond AND/OR/NOT/parentheses/quotes/AREA, ClinicalTrials.gov supports operators like RANGE for date-bounded searches:
```
AREA[ConditionSearch]COVID-19 and AREA[StartDate]RANGE[01/01/2022, MAX]
```
retrieves the most recent COVID-19 trials. See ClinicalTrials.gov's [operator reference](https://www.clinicaltrials.gov/api/gui/ref/expr) for the complete list.
### Test Your Search Before Running It
Copy your search string into the "Other Terms" field at [clinicaltrials.gov](https://www.clinicaltrials.gov/) to preview result volume and quality before running an Automatic Search in Nested Knowledge. Nested Knowledge's API integration uses the current ClinicalTrials.gov platform; testing against ["Classic ClinicalTrials.gov"](https://classic.clinicaltrials.gov/) — being retired — can return results that differ by roughly 1% due to differences between the two versions.
### Copy A Query You've Already Built
If you've already built a search on the ClinicalTrials.gov website and want it running on a schedule in Nested Knowledge instead of re-running it manually:
1. Enter your search terms as usual on ClinicalTrials.gov, then select **Search**.
2. In the search bar, select **Advanced Search**.
3. Select **Expert Search**, in the top right.
4. Copy the query now shown in the correct syntax, and paste it into [Automatic Search](/review-workflow/literature-search/add-search/automatic-search.md) in Nested Knowledge.
### Search Results In Your Nest
Run ClinicalTrials.gov searches from **Automatic Search**. Results are automatically marked as Related Reports, since a trial registration and its eventual publication typically describe the same underlying study.
### FAQs
Should I search ClinicalTrials.gov instead of PubMed, or alongside it?
Alongside it. ClinicalTrials.gov covers trial registrations, not journal publications — the two sources answer different questions and most reviews that need trial-level completeness run both.
Why does my ClinicalTrials.gov search return different counts when I test it on the website versus running it in Nested Knowledge?
Testing against "Classic ClinicalTrials.gov" instead of the current platform is the most common cause — the two versions can differ by about 1%. Confirm you're testing on the current site.
Can I use the same query syntax as PubMed here?
No — ClinicalTrials.gov uses AREA-based field search rather than PubMed's `[FIELD]` tags, so a query needs rewriting to move between the two.
---
# Agent Instructions
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## Querying This Documentation
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Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:
```
GET https://docs.nested-knowledge.com/guides/write-a-search-query/clinicaltrials.gov.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.
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Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.