Pipeline for the flagship project (WP2)

This analysis is broken up into Part 1, analyses deployed to analysts with indiviudal-level data access in each biobank, and Part 2, analyses done on summary statistics to draw conclusions across biobanks. In each step, this README text explains what parts of the scripts need to be adjusted to your file paths and dataset.

Dependencies

These scripts assume you have plink-1.9 and R v4.1.0 or higher installed on your biobank computing system. Required R libraries: data.table, tidyverse/dplyr

Citation

Jermy, B., Läll, K., Wolford, B.N. et al. A unified framework for estimating country-specific cumulative incidence for 18 diseases stratified by polygenic risk. Nat Commun 15, 5007 (2024). https://doi.org/10.1038/s41467-024-48938-2

License

This code is available under MIT license.

Contact

If you have questions please contact brookewo@ntnu.no. Issues can be raised with the Git Issues feature.

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Part 1: Biobank-specific analyses

Step 1: Define phenotypes

Step 1a: Run UKBPhenotyper.R

• Run UKBBPhenotyper.R (can be found within Phenotyping folder) to define the phenotypes required for this analysis. Note this will require you to also download the file UKBB_definitions_demo_TEST.csv. The script assumes ICD code individual level data is in long format.

• Please check your ICD codes are in the correct format within the individual level data before applying the code.

• Phenotypes of interest after running this script are (you can subset the file to just these):

  1. C3_CANCER (All cancers)
  2. K11_APPENDACUT (Appendicitis)
  3. J10_ASTHMA (Asthma)
  4. I9_AF (Atrial fibrillation)
  5. C3_BREAST (Breast cancer
  6. I9_CHD (Coronary heart disease)
  7. C3_COLORECTAL (Colorectal cancer)
  8. G6_EPLEPSY (Epilepsy)
  9. GOUT (Gout)
  10. COX_ARTHROSIS (Hip osteoarthritis)
  11. KNEE_ARTHROSIS (Knee osteoarthritis)
  12. F5_DEPRESSIO (Major depressive disorder)
  13. C3_MELANOMA_SKIN (Malignant skin melanoma)
  14. C3_PROSTATE (Prostate cancer)
  15. RHEUMA_SEROPOS_OTH (Rheumatoid arthritis)
  16. T1D (Type 1 diabetes)
  17. T2D (Type 2 diabetes)
  18. ILD (Interstitial lung disease)
  19. C3_BRONCHUS_LUNG (Lung cancer)

• To make sure the script can separate between ICD 10 and ICD 9 codes, it places a '10x' or a '9x' at the start of the code according to whether the code is ICD9 or 10.

• The regex pattern then searches for strings starting with 10x or 9x before identifying the codes themselves.

• Note: if an individual does not have any of the ICD codes highlighted in the above definitions, they will not be included within the final dataset. These controls must be manually added to the final phenotype file.

Step 1b: Construct phenotype file

• The phenotype file will include all variables required to construct hazard ratios, i.e. genetic principal components, ancestry allocation, variables that allow you to control for technical artefacts (genotype batch, cohort etc.). Please use whatever variables currently exist within your biobank. These do not need to be harmonised.

• To learn more about the variables that are required, please read: https://docs.google.com/document/d/1GbZszpPeyf-hyb0V_YDx828YbM7woh8OBJhvzkEwo2g/edit Note: you can currently ignore the requirement to define smoking and education.

Step 1c: Run baseline_stats.R (in Phenotyping folder)

• We want to calculate summary statistics on the phenotype file
• Execute Phenotyping/baseline_stats.R after setting custom variables:

1. Line 10 - Specify phenotype filename.
2. Line 11 - Specify biobank name/acronym
3. Line 12 - Specify output directory.
4. Line 14 - Add phenotype names as strings only if you are missing any phenotypes in your dataset.
5. Line 15 - Logical variable specifying if birth is the baseline (default is that START_OF_FOLLOWUP is another recruitment date)

• Output files are "_baseline_summary_stats.csv" and "_age_quartiles.csv".

Step 2: Download Adjusted Summary Statistics

• All pre-adjusted summary statistics can be found here. Email brookewo@ntnu.no for access.

• Download the pre-adjusted summary statistics created using MegaPRS that correspond to the build of the genome for your biobank.

• hg19 files found here / hg38 files found here. Hg19 contains rsids whereas hg38 contains variant IDs in the format CHR_POS_REF_ALT.

Step 3: Merge variant IDs to match those within the .bim file.

Note - only to be performed if the genome build is hg38 and the variant ID structure is CHR_POS_REF_ALT.

• Run script hg38_biobankadjustments.R

• This script is required for all biobanks which have a genome build of hg38/where the variant ID structure within the bim file is in the form CHR_POS_REF_ALT.

• Due to the nature of the conversion to hg38 within the pre-adjusted summary statistics, we cannot be sure what the REF or ALT allele is within your bim file as we have relied on those within the summary statistics themselves. As such, both combinations are currently saved within the sum stats.

• The script reads in your bim file and identifies which variant ID is contained within your bim file and the summary statistics and creates a final snp list for the adjusted summary statistics.

• For this script to work you will have to:

  1. Line 9 - Adjust the path within the 'bim' variable to read in your biobanks bim file.
  2. Line 19 - Adjust the path to the location of the adjusted summary statistics downloaded during step 1. Note: I have assumed you have mainted the same filename structure as when you downloaded the files.
  3. Line 40 - Adjust the path to the location where you wish to save the amended summary statistics. Recommended to just overwrite the original summary statistics so keep the same path as specified in line 19. You may want to test the code before saving initially just to make sure it is behaving as expected.

Step 4: Compute PRS using Plink

• Note: if you use a job scheduler which allows multiple jobs to be submitted, please adjust the script below and create a single job for each phenotype. This script assumes an interactive job and loops over phenotypes which will be much much slower than running in parallel.

If your plink files are not split by chromosome

• Run script GeneratePRS.sh

• For this script to work you will have to:

  1. Line 8 - Specify the path where PRS are to be saved.
  2. Line 9 - Specify the path of the downloaded summary statistics from Step 2.
  3. Line 10 - Specify the path to the directory where the allele frequencys are stored.
  4. Line 11 - Optional: If you want to speed up computation and calculate PRS on a subset of SNPs, i.e. hapmap, you can specify the list here.
  5. Line 12 - Specify the path to the directory where the genotypes are stored (it is likely line 8 and line 10 will have the same path).
  6. Line 19 - Specify the path to plink. If you do not have plink2 installed, also change to the version used by your biobank.
  7. Line 20 - Change 'genotype_plink_files' to the name of your genotype files.
  8. Line 21 - Optional: Name of your SNP list file.
  9. Line 22 - Change 'frequency_file' to the name of your file containing allele frequencies.
  10. Line 24 - Select 19 or 38 depending on the build of your biobanks genome. Also remove square brackets surrounding the number.

• Note: If you do not have a file containing allele frequencies, we recommend producing one before computing PRS as otherwise plink will redo this step for every phenotype.

If your plink files are split by chromosome

Step 4a: Run script GeneratePRS_IndividualChr.sh

• For this script to work you will have to:
  1. Line 8 - Specify the path where PRS are to be saved.
  2. Line 9 - Specify the path of the downloaded summary statistics from Step 2.
  3. Line 10 - Specify the path to the directory where the allele frequencys are stored.
  4. Line 11 - Optional: If you want to speed up computation and calculate PRS on a subset of SNPs, i.e. hapmap, you can specify the list here.
  5. Line 12 - Specify the path to the directory where the genotypes are stored (it is likely line 8 and line 10 will have the same path).
  6. Line 19 - Specify the path to plink. If you do not have plink2 installed, also change to the version used by your biobank.
  7. Line 20 - Change 'genotype_plink_files' to the name of your genotype files. When the plink filename refers to the number of the chromosome, replace this with a ${j} to allow the script to run through the chromosomes.
  8. Line 21 - Optional: Name of your SNP list file.
  9. Line 22 - Change 'frequency_file' to the name of your file containing allele frequencies.
  10. Line 24 - Select 19 or 38 depending on the build of your biobanks genome. Also remove square brackets surrounding the number.

Step 4b: Run script PRSSummationOverChr.R

• This script simply sums over the PRS found in individual chromosomes to get the total PRS.

• For this script to work you will have to:

  1. Line 10, 18 and 31 - Specify the file path of the chromosome specific score files.

Step 5: Calculate hazard ratios between PRS and Phenotype - survival analysis

• Note: the scripts have five assumptions.
  1. You have a phenotype file with case control assignments and dates of first diagnosis for each phenotype. More generally, you have the same column names as specified in the phenotype file specifications.
  2. You have been able to allocate genetic ancestry for the participants within your biobank. This does not have to be harmonized, any approach taken by your biobank will suffice for this analysis.
  3. You have kept the same short hand names for the phenotypes as within FinnGen (column B).
  4. You have kept the same naming structure for the PRS files as when you downloaded them.
  5. A SEX column exists in your phenotype file and it is coded as a factor with two levels 'male' and 'female' and 'female' is the reference.

Step 5a: Run script HazardRatioperStandardDeviation.R - Can be found within the PRS folder.

• For this script to work you will have to:
  1. Line 20 - Amend "path/to/pheno_file" to the path of your phenotype file. See assumption 1.
  2. Line 25 - Amend "path/to/PRS" to the path of your score file.
  3. Lines 31 - Change 'ENTER_ID' to correspond to the ID column within your biobank, i.e. FINNGENID. Note: there may be redundant info taken by choosing the two columns. If this is the case, just select one of the IDs.
  4. Line 41 - If each section does not subset individuals to those of european ancestries, remove and subset to each ancestry yourself.
  5. Lines 53,60,61 - Add to the formula any variables you would normally use to control for technical artefacts within your genotype data, i.e. genotype batch/assessment centre.
  6. Line 95 - Amend "file/path/to/output/HRperSD_[ENTER_BIOBANK_NAME].csv" to your chosen output.

Step 5b: Run script HazardRatioperSD_AgeStratified.R - Can be found within the PRS folder.

• For this script to work you will have to:
  1. Line 42 - Amend "path/to/pheno_file" to the path of your phenotype file. See assumption 1.
  2. Line 47 - Amend "path/to/PRS" to the path of your score file.
  3. Lines 53 - Change 'ENTER_ID' to correspond to the ID column within your biobank, i.e. FINNGENID. Note: there may be redundant info taken by choosing the two columns. If this is the case, just select one of the IDs.
  4. Line 63 - If each section does not subset individuals to those of european ancestries, remove and subset to each ancestry yourself.
  5. Line 90 - Add to the formula any variables you would normally use to control for technical artefacts within your genotype data, i.e. genotype batch/assessment centre.
  6. Line 114 - Amend "file/path/to/output/HRperSD_[ENTER_BIOBANK_NAME].csv" to your chosen output.

Step 5c: Run script HazardRatioperSD_AgeandSexStratified.R - Can be found within the PRS folder.

• For this script to work you will have to:
  1. Line 42 - Amend "path/to/pheno_file" to the path of your phenotype file. See assumption 1.
  2. Line 47 - Amend "path/to/PRS" to the path of your score file.
  3. Lines 53 - Change 'ENTER_ID' to correspond to the ID column within your biobank, i.e. FINNGENID. Note: there may be redundant info taken by choosing the two columns. If this is the case, just select one of the IDs.
  4. Line 63 - If each section does not subset individuals to those of european ancestries, remove and subset to each ancestry yourself.
  5. Line 94 - Add to the formula any variables you would normally use to control for technical artefacts within your genotype data, i.e. genotype batch/assessment centre.
  6. Line 118 - Amend "file/path/to/output/HR_AgeStratified_[ENTER_BIOBANK_NAME].csv" to your chosen output.

Step 5d: Run script HazardRatio_SexInteraction.R - Can be found within the PRS folder.

• For this script to work you will have to:
  1. Line 20 - Amend "path/to/pheno_file" to the path of your phenotype file. See assumption 1.
  2. Line 25 - Amend "path/to/PRS" to the path of your score file.
  3. Lines 31 - Change 'ENTER_ID' to correspond to the ID column within your biobank, i.e. FINNGENID. Note: there may be redundant info taken by choosing the two columns. If this is the case, just select one of the IDs.
  4. Line 41 - If each section does not subset individuals to those of european ancestries, remove and subset to each ancestry yourself.
  5. Line 53 - Add to the formula any variables you would normally use to control for technical artefacts within your genotype data, i.e. genotype batch/assessment centre.
  6. Line 95 - Amend "file/path/to/output/HR_SexInteraction_[ENTER_BIOBANK_NAME].csv" to your chosen output.

Step 5e: Run script HazardRatio_FullSample.R - Can be found within the PRS folder.

• For this script to work you will have to:
  1. Line 27 - Amend "path/to/pheno_file" to the path of your phenotype file. See assumption 1.
  2. Line 32 - Amend "path/to/PRS" to the path of your score file.
  3. Lines 38 - Change 'ENTER_ID' to correspond to the ID column within your biobank, i.e. FINNGENID. Note: there may be redundant info taken by choosing the two columns. If this is the case, just select one of the IDs.
  4. Line 48 - If each section does not subset individuals to those of european ancestries, remove and subset to each ancestry yourself.
  5. Line 68 - Add to the formula any variables you would normally use to control for technical artefacts within your genotype data, i.e. genotype batch/assessment centre.
  6. Line 107 - Amend "file/path/to/output/HR_FullSample[ENTER_BIOBANK_NAME].csv" to your chosen output.

Step 5f: Run script HazardRatio_SexStratified.R - Can be found within the PRS folder.

• For this script to work you will have to:
  1. Line 28 - Amend "path/to/pheno_file" to the path of your phenotype file. See assumption 1.
  2. Line 33 - Amend "path/to/PRS" to the path of your score file.
  3. Lines 39 - Change 'ENTER_ID' to correspond to the ID column within your biobank, i.e. FINNGENID. Note: there may be redundant info taken by choosing the two columns. If this is the case, just select one of the IDs.
  4. Line 49 - If each section does not subset individuals to those of european ancestries, remove and subset to each ancestry yourself.
  5. Lines 74,111 - Add to the formula any variables you would normally use to control for technical artefacts within your genotype data, i.e. genotype batch/assessment centre.
  6. Lines 144 and 145 - Amend "file/path/to/output/HR_[Male/Female]Sample[ENTER_BIOBANK_NAME].csv" to your chosen output.

Step 5g: Run script HazardRatio_AgeStratified.R - Can be found within the PRS folder.

• For this script to work you will have to:
  1. Line 49 - Amend "path/to/pheno_file" to the path of your phenotype file. See assumption 1.
  2. Line 54 - Amend "path/to/PRS" to the path of your score file.
  3. Lines 60 - Change 'ENTER_ID' to correspond to the ID column within your biobank, i.e. FINNGENID. Note: there may be redundant info taken by choosing the two columns. If this is the case, just select one of the IDs.
  4. Line 70 - If each section does not subset individuals to those of european ancestries, remove and subset to each ancestry yourself.
  5. Line 104 - Add to the formula any variables you would normally use to control for technical artefacts within your genotype data, i.e. genotype batch/assessment centre.
  6. Line 149 - Amend "file/path/to/output/HR_AgeStratified_[ENTER_BIOBANK_NAME].csv" to your chosen output.

Step 5h: Run script HazardRatio_AgeandSexStratified.R - Can be found within the PRS folder.

• For this script to work you will have to:
  1. Line 49 - Amend "path/to/pheno_file" to the path of your phenotype file. See assumption 1.
  2. Line 54 - Amend "path/to/PRS" to the path of your score file.
  3. Lines 60 - Change 'ENTER_ID' to correspond to the ID column within your biobank, i.e. FINNGENID. Note: there may be redundant info taken by choosing the two columns. If this is the case, just select one of the IDs.
  4. Line 70 - If each section does not subset individuals to those of european ancestries, remove and subset to each ancestry yourself.
  5. Line 108 - Add to the formula any variables you would normally use to control for technical artefacts within your genotype data, i.e. genotype batch/assessment centre.
  6. Line 153 - Amend "file/path/to/output/HR_AgeStratified_[ENTER_BIOBANK_NAME].csv" to your chosen output.

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Part 2: Analyses on summary statistics

Step 1: Model selection

Decide the best model according to the hazard ratios from age and sex stratification (no stratification, sex stratification, age stratification and age and sex stratification). See the manuscript for requirements for choosing a model. ModelSelection_Age.R and ModelSelection_AgeandSex.R conduct model selection from the hazard ratios. Essentially, the scripts meta-analyse the European hazard ratios and fit a weighted linear regression to each quartile to see whether the slope is significant. Age and Sex stratification goes a step further by testing whether the slopes differ by sex.

.csv files for the hazard ratios, age quartiles, and output are hardcoded and should be changed to reflect your filepaths (lines 7, 12, 20, 26, 38, 44, 109, 197).

Step 2: Estimate lifetime risk

Once you have decided the appropriate model you will estimate lifetime risk. If ‘Age’ or ‘Age and Sex’ are the chosen models an extra couple of steps are required.

Age:

Age and Sex:
01_AgeandSexStrat_SplineFitting_Bootstrap.R and 01_AgeandSexStrat_SplineFitting.R This does the exact same thing as the ModelSelection scripts, however, it is country-specific. Once you have these hazard ratios you can place them into associated lifetime risk script and its bootstrap version. 02_AgeandSexStrat_LifetimeRiskEstimation_Bootstrap.R and 02_AgeandSexStrat_LifetimeRiskEstimation.R

Sex:
03_Sex_LifetimeRiskEstimation_Bootstrap.R and 03_Sex_LifetimeRiskEstimation.R

No stratification:
04_LifetimeRiskEstimation_Bootstrap.R and 04_LifetimeRiskEstimation.R

Age:
05_Age_SplineFitting_Bootstrap.R and 05_Age_SplineFitting.R
06_Age-LifetimeRiskEstimation_Bootstrap.R and 06_Age_LifetimeRiskEstimation.R

Using these as a template, you can adjust the scripts to the phenotype and the countries that have been assessed.

In terms of how the Lifetime Risk is estimated, the aim of the equation is to figure out the incidence per age and PRS group using the total incidence of this age group from the global burden of disease and the hazard ratio relative to the average PRS group (40-60%). In the equation, ‘I’ stands for total incidence and ‘I0’ is the baseline incidence (average PRS group). We assume the hazard ratio is equivalent to the incident rate ratio which allows us to calculate the incidence attributable to each group. To then convert this to lifetime risk, we use the method specified in the supplementary appendix of this paper.

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