ClinVar API Reference

Base URLs

• NCBI E-utilities: https://eutils.ncbi.nlm.nih.gov/entrez/eutils
• ClinVar web API (VCV): https://www.ncbi.nlm.nih.gov/clinvar
• NCBI Variation Services: https://api.ncbi.nlm.nih.gov/variation/v0

Authentication

• E-utilities: No key required, but strongly recommended. Register at https://www.ncbi.nlm.nih.gov/account/ to get an api_key.
• Without key: 3 requests/second. With key: 10 requests/second.
• Append &api_key=YOUR_KEY to all E-utility requests.

Rate Limits

• Without API key: 3 req/sec
• With API key: 10 req/sec

Key Endpoints

1. Search ClinVar (esearch)

GET https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=clinvar&term={query}&retmode=json

Example — search for BRCA1 pathogenic variants:

GET https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=clinvar&term=BRCA1[gene]+AND+pathogenic[clinical_significance]&retmode=json&retmax=10

Returns JSON with idlist of ClinVar Variation IDs.

2. Fetch ClinVar Records (esummary)

GET https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esummary.fcgi?db=clinvar&id={id_list}&retmode=json

Example:

GET https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esummary.fcgi?db=clinvar&id=37088,37087&retmode=json

Returns JSON with clinical significance, variant name, gene, conditions, review status.

3. Full Record (efetch)

GET https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=clinvar&id={id}&rettype=vcv&is_variationid&retmode=xml

Note: ClinVar efetch returns XML only (no JSON for efetch).

4. Resolve HGVS/SPDI before searching ClinVar

NCBI Variation Services normalizes variants; it has no /clinvar suffix endpoint. Use GET https://api.ncbi.nlm.nih.gov/variation/v0/hgvs/{hgvs}/contextuals, then /spdi/{spdi}/rsids. Search ClinVar with the resolved rsID (or a validated HGVS expression) using ESearch. An rsID can represent multiple alternate alleles: compare accession, assembly, position and alleles in the ClinVar record. SPDI positions are zero-based; HGVS genomic positions are one-based.

5. ClinVar VCV/RCV Direct Access

GET https://www.ncbi.nlm.nih.gov/clinvar/variation/{variation_id}/?redir=vcv

This returns HTML. For programmatic access, use E-utilities or the Variation Services API.

Useful Search Qualifiers

• [gene] — gene symbol (e.g., BRCA1[gene])
• [clinical_significance] — pathogenic, likely_pathogenic, benign, uncertain_significance
• [molecular_consequence] — missense, nonsense, frameshift, etc.
• [review_status] — criteria_provided_single_submitter, reviewed_by_expert_panel, etc.
• [condition] — disease name

Response Format

• esearch/esummary: JSON (with retmode=json)
• efetch: XML only for ClinVar
• Variation Services: JSON

esummary Response Key Fields

{
  "result": {
    "37088": {
      "uid": "37088",
      "title": "NM_003238.6(TGFB2):c.687C>A (p.Cys229Ter)",
      "germline_classification": {
        "description": "Pathogenic",
        "last_evaluated": "2025/09/08 00:00",
        "review_status": "criteria provided, single submitter",
        "fda_recognized_database": "",
        "trait_set": [
          {
            "trait_xrefs": [
              {
                "db_source": "MedGen",
                "db_id": "C3553762"
              },
              {
                "db_source": "MONDO",
                "db_id": "MONDO:0013897"
              },
              {
                "db_source": "OMIM",
                "db_id": "614816"
              }
            ],
            "trait_name": "Loeys-Dietz syndrome 4"
          }
        ]
      },
      "genes": [
        {
          "symbol": "TGFB2",
          "geneid": "7042",
          "strand": "+",
          "source": "submitted"
        }
      ]
    }
  }
}

Somatic clinical impact and oncogenicity are separate classifications; inspect somatic_clinical_impact and oncogenicity when present. Do not conflate these with germline classification or discard conflicting submissions.

Notes

• Combine esearch + esummary for search-then-fetch workflows.
• For bulk downloads, use ClinVar FTP: https://ftp.ncbi.nlm.nih.gov/pub/clinvar/