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skills/FreedomIntelligence/OpenClaw-Medical-Skills/tooluniverse-gwas-study-explorer

tooluniverse-gwas-study-explorer

1
FreedomIntelligence/OpenClaw-Medical-Skills·Biology Medicine and Bioinformatics·Audit pending·Snapshot c5ed34cc5302

Summary

This source did not publish a separate summary. Review SKILL.md before using the skill.

SKILL.md

GWAS Study Deep Dive & Meta-Analysis

Compare GWAS studies, perform meta-analyses, and assess replication across cohorts


Overview

The GWAS Study Deep Dive & Meta-Analysis skill enables comprehensive comparison of genome-wide association studies (GWAS) for the same trait, meta-analysis of genetic loci across studies, and systematic assessment of replication and study quality. It integrates data from the NHGRI-EBI GWAS Catalog and Open Targets Genetics to provide a complete picture of the genetic architecture of complex traits.

Key Capabilities

  1. Study Comparison: Compare all GWAS studies for a trait, assessing sample sizes, ancestries, and platforms
  2. Meta-Analysis: Aggregate effect sizes across studies and calculate heterogeneity statistics
  3. Replication Assessment: Identify replicated vs novel findings across discovery and replication cohorts
  4. Quality Evaluation: Assess statistical power, ancestry diversity, and data availability

Use Cases

1. Comprehensive Trait Analysis

Scenario: "I want to understand all available GWAS data for type 2 diabetes"

Workflow:

  • Search for all T2D studies in GWAS Catalog
  • Filter by sample size and ancestry
  • Extract top associations from each study
  • Identify consistently replicated loci
  • Assess ancestry-specific effects

Outcome: Complete landscape of T2D genetics with replicated findings and population-specific signals

2. Locus-Specific Meta-Analysis

Scenario: "Is the TCF7L2 association with T2D consistent across all studies?"

Workflow:

  • Retrieve all TCF7L2 (rs7903146) associations for T2D
  • Calculate combined effect size and p-value
  • Assess heterogeneity (I² statistic)
  • Generate forest plot data
  • Interpret heterogeneity level
  • Outcome: Quantitative assessment of effect size consistency with heterogeneity interpretation

    3. Replication Analysis

    Scenario: "Which findings from the discovery cohort replicated in the independent sample?"

    Workflow:

    • Get top hits from discovery study
    • Check for presence and significance in replication study
    • Assess direction consistency
    • Calculate replication rate
    • Identify novel vs failed replication

    Outcome: Systematic replication report with success rates and failed findings

    4. Multi-Ancestry Comparison

    Scenario: "Are T2D loci consistent across European and East Asian populations?"

    Workflow:

    • Filter studies by ancestry
    • Compare top associations between populations
    • Identify shared vs population-specific loci
    • Assess allele frequency differences
    • Evaluate transferability of genetic risk scores

    Outcome: Ancestry-specific genetic architecture with transferability assessment


    Statistical Methods

    Meta-Analysis Approach

    This skill implements standard GWAS meta-analysis methods:

    Fixed-Effects Model:

    • Used when heterogeneity is low (I² < 25%)
    • Weights studies by inverse variance
    • Assumes true effect size is the same across studies

    Random-Effects Model (recommended when I² > 50%):

    • Accounts for between-study variation
    • More conservative than fixed-effects
    • Better for diverse ancestries or methodologies

    Heterogeneity Assessment:

    The I² statistic measures the percentage of variance due to between-study heterogeneity:

    I² = [(Q - df) / Q] × 100%
    
    where Q = Cochran's Q statistic
          df = degrees of freedom (n_studies - 1)
    

    Interpretation Guidelines:

    • I² < 25%: Low heterogeneity → fixed-effects appropriate
    • I² = 25-50%: Moderate heterogeneity → investigate sources
    • I² = 50-75%: Substantial heterogeneity → random-effects preferred
    • I² > 75%: Considerable heterogeneity → meta-analysis may not be appropriate

    Sources of Heterogeneity

    Common reasons for high I²:

    1. Ancestry differences: Different allele frequencies and LD structure
    2. Phenotype heterogeneity: Trait definition varies across studies
    3. Platform differences: Imputation quality and coverage
    4. Winner's curse: Discovery studies overestimate effect sizes
    5. Cohort characteristics: Age, sex, environmental factors

    Recommendations:

    • Perform subgroup analysis by ancestry
    • Use meta-regression to investigate sources
    • Consider excluding outlier studies
    • Apply genomic control correction

    Study Quality Assessment

    Quality Metrics

    The skill evaluates studies based on:

    1. Sample Size:

    • Power to detect associations (80% power requires n > 10,000 for OR=1.2)
    • Precision of effect size estimates
    • Ability to detect modest effects

    2. Ancestry Diversity:

    • Single-ancestry vs multi-ancestry
    • Population stratification control
    • Transferability of findings

    3. Data Availability:

    • Summary statistics available for meta-analysis
    • Individual-level data vs summary-level
    • Imputation quality scores

    4. Genotyping Quality:

    • Platform density and coverage
    • Imputation reference panel
    • Quality control measures

    5. Statistical Rigor:

    • Genome-wide significance threshold (p < 5×10⁻⁸)
    • Multiple testing correction
    • Replication in independent cohort

    Quality Tiers

    Tier 1 (High Quality):

    • n ≥ 50,000
    • Summary statistics available
    • Multi-ancestry or large single-ancestry
    • Imputed to high-quality reference
    • Independent replication

    Tier 2 (Moderate Quality):

    • n ≥ 10,000
    • Standard GWAS platform
    • Adequate power for common variants
    • Some data availability

    Tier 3 (Limited):

    • n < 10,000
    • Limited power
    • May miss modest effects
    • Use with caution

    Best Practices

    Before Meta-Analysis

    1. Check phenotype consistency: Ensure studies measure the same trait
    2. Verify ancestry overlap: High heterogeneity expected if ancestries differ
    3. Harmonize alleles: Align effect alleles across studies
    4. Quality control: Exclude low-quality studies or associations

    Interpreting Results

    1. Genome-wide significance: p < 5×10⁻⁸ (Bonferroni for ~1M independent tests)
    2. Replication threshold: p < 0.05 in independent cohort
    3. Direction consistency: Effect should be same direction across studies
    4. Heterogeneity: I² > 50% suggests caution in interpretation

    Common Pitfalls

    ❌ Don't:

    • Meta-analyze without checking heterogeneity
    • Ignore ancestry differences
    • Over-interpret nominal p-values
    • Assume replication failure means false positive

    ✅ Do:

    • Always report I² statistic
    • Perform sensitivity analyses
    • Consider ancestry-stratified analysis
    • Account for winner's curse in discovery studies

    Limitations & Caveats

    Data Limitations

    1. Incomplete Overlap: Studies may analyze different SNPs
    2. Cohort Overlap: Some cohorts participate in multiple studies (inflates significance)
    3. Publication Bias: Significant findings more likely to be published
    4. Winner's Curse: Discovery studies overestimate effect sizes
    5. Imputation Quality: Varies across studies and populations

    Statistical Limitations

    1. Heterogeneity: High I² may preclude meaningful meta-analysis
    2. Sample Size Differences: Large studies dominate fixed-effects models
    3. Allele Frequency Differences: Same variant has different effects across ancestries
    4. Linkage Disequilibrium: Fine-mapping needed to identify causal variants
    5. Gene-Environment Interactions: Not captured in standard meta-analysis

    Interpretation Guidelines

    When I² > 75%:

    • Meta-analysis results should be interpreted with extreme caution
    • Investigate sources of heterogeneity systematically
    • Consider ancestry-specific or subgroup analyses
    • Descriptive comparison may be more appropriate than meta-analysis

    When Studies Conflict:

    • Check for methodological differences
    • Verify phenotype definitions match
    • Investigate population stratification
    • Consider conditional analysis

    Scientific References

    Key Publications

    1. GWAS Best Practices:

      • Visscher et al. (2017). "10 Years of GWAS Discovery" American Journal of Human Genetics 101(1): 5-22
      • PMID: 28686856
      • DOI: 10.1016/j.ajhg.2017.06.005
    2. Meta-Analysis Methods:

      • Evangelou & Ioannidis (2013). "Meta-analysis methods for genome-wide association studies and beyond" Nature Reviews Genetics 14: 379-389
      • PMID: 23657481
    3. Heterogeneity Interpretation:

      • Higgins et al. (2003). "Measuring inconsistency in meta-analyses" BMJ 327: 557-560
      • PMID: 12958120
    4. Multi-Ancestry GWAS:

      • Peterson et al. (2019). "Genome-wide Association Studies in Ancestrally Diverse Populations" Nature Reviews Genetics 20: 409-422
      • PMID: 30926972
    5. Replication Standards:

      • Chanock et al. (2007). "Replicating genotype-phenotype associations" Nature 447: 655-660
      • PMID: 17554299

    Tools Used

    GWAS Catalog API

    • gwas_search_studies: Find studies by trait
    • gwas_get_study_by_id: Get detailed study metadata
    • gwas_get_associations_for_study: Retrieve study associations
    • gwas_get_associations_for_snp: Get SNP associations across studies
    • gwas_search_associations: Search associations by trait

    Open Targets Genetics GraphQL API

    • OpenTargets_search_gwas_studies_by_disease: Disease-based study search
    • OpenTargets_get_gwas_study: Detailed study information with LD populations
    • OpenTargets_get_variant_credible_sets: Fine-mapped loci for variant
    • OpenTargets_get_study_credible_sets: All credible sets for study
    • OpenTargets_get_variant_info: Variant annotation and allele frequencies

    Glossary

    Association: Statistical relationship between a genetic variant and a trait

    Credible Set: Set of variants likely to contain the causal variant (from fine-mapping)

    Effect Size: Magnitude of genetic association (beta coefficient or odds ratio)

    Fine-Mapping: Statistical method to identify causal variants within a locus

    Genome-Wide Significance: p < 5×10⁻⁸, accounting for ~1M independent tests

    Heterogeneity (I²): Percentage of variance due to between-study differences

    L2G (Locus-to-Gene): Score predicting which gene is affected by a GWAS locus

    LD (Linkage Disequilibrium): Non-random association of alleles at different loci

    Meta-Analysis: Statistical combination of results from multiple studies

    Replication: Independent confirmation of an association in a new cohort

    Summary Statistics: Per-SNP statistics (p-value, beta, SE) from GWAS

    Winner's Curse: Overestimation of effect size in discovery studies


    Next Steps

    After running this skill, consider:

    1. Fine-Mapping: Use credible sets from Open Targets to identify causal variants
    2. Functional Follow-Up: Investigate biological mechanisms of replicated loci
    3. Genetic Risk Scores: Calculate polygenic risk scores using validated loci
    4. Drug Target Identification: Use L2G scores to prioritize therapeutic targets
    5. Cross-Trait Analysis: Look for pleiotropy with related traits

    Version History

    • v1.0 (2026-02-13): Initial release with study comparison, meta-analysis, and replication assessment

    Created by: ToolUniverse GWAS Analysis Team Last Updated: 2026-02-13 License: Open source (MIT)

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