BioProject to study, via the ENA portal

Route id: bioproject->study:ena_filereport Provider: EBI ENA portal Direction: PRJNA/PRJEB/PRJDB → SRP/ERP/DRP

curl -s 'https://www.ebi.ac.uk/ena/portal/api/filereport?accession=PRJNA988806&result=read_run&fields=secondary_study_accession&format=tsv&limit=0'

Measured

Corpus: reprocessed-prj, all 12,755 BioProjects. Surveyed: 2026-09-15.

Resolved	12,732
Empty	23
Failed	0
Distinct studies	12,748

12,748 studies for 12,732 projects. Close to one-to-one, but not exactly: a handful of projects carry more than one secondary study accession, so code that treats the mapping as a function will drop data on those. The 23 empties are the same projects every ENA route finds nothing for.

Why this direction is asked at all

A study accession is what ArrayExpress declares in its IDF and what several older tools take as their handle, so a BioProject has to be convertible to one. It is also the cheapest way to confirm that a project is EBI-visible at all: result=read_run rows are runs, so a study returned here is a study with data behind it.