Multi-Sample Analysis

As of March 2022, PharmCAT only takes a single-sample VCF. If a multi-sample VCF is provided, only the first sample will be annotated. However, PharmCAT can generate a PGx report in a matter of seconds for a preprocessed VCF. The fast runtime of PharmCAT allows you to batch-annotate VCFs, with a little help from a bit of scripting, to scale from a few dozen samples to a biobank-scale cohorts in an efficient manner.

This documentation shares concrete examples of how to use PharmCAT to batch process multiple samples in a High-Performance Computing (HPC) environment. We expect readers to be familiar with using both PharmCAT's VCF Preprocessor and the core PharmCAT tool.

Need an interactive tutorial? we have a tutorial available that walks you through working with real genetic data sets.

Table of contents

  1. Example using the Stanford Sherlock HPC
    1. Preprocessing the data
      1. Case 1 - single-sample VCFs
      2. Case 2 - multi-sample VCF
      3. Case 3 - multi-sample VCF divided by chromosome or into consecutive genetic blocks
    2. Running PharmCAT
      1. Batch outside calls
    3. Running individual components
      1. Named Allele Matcher
      2. Phenotyper - use the Named Allele Matcher JSON data
      3. Reporter
    4. Extracting PharmCAT JSON content into TSV
      1. Example command
  2. Example with the Penn Medicine Biobank
    1. Preprocessing the data
    2. Running PharmCAT
    3. Reading the PharmCAT calls into Python
  3. Reference

Example using the Stanford Sherlock HPC

This part uses the VCFs on multiple GeT-RM samples1 generated from the 30x high-coverage WGS sequencing performed by the New York Genome Center (NYGC)2. The job was run on the Stanford Sherlock cluster, a High-Performance Computing (HPC) cluster which uses Slurm as an open-source resource manager and job scheduler. The scripts to run PharmCAT on the Stanford Sherlock cluster is written in shell programming language and can be easily adapted to another HPC environment supported by a different job scheduler.

Preprocessing the data

This section provides examples for working with different types of input VCFs.

Case 1 - single-sample VCFs

If your genetic data is already stored in single-sample VCFs, you are one step closer to running the PharmCAT. We recommend the users to still run the PharmCAT VCF Preprocessor to ensure the appropriate variant representation format, which can be achieved by the following command.

On the command line:

$ python3 pharmcat_vcf_preprocessor.py -vcf <single_sample_vcf>

For example:

$ cd PharmCAT-tutorial/
$ cat data/single_sample_vcf_list.txt
data/PharmCAT_tutorial_get-rm_wgs_30x_grch38.NA18526.vcf.bgz
data/PharmCAT_tutorial_get-rm_wgs_30x_grch38.NA18565.vcf.bgz
data/PharmCAT_tutorial_get-rm_wgs_30x_grch38.NA18861.vcf.bgz

Sample script:

# run the preprocessor iteratively across single-sample VCFs
for SINGLE_VCF in $(cat data/single_sample_vcf_list.txt)
do
  # run the PharmCAT VCF Preprocessor for a single-sample VCF
  python3 pharmcat_vcf_preprocessor.py -vcf "$SINGLE_VCF"
done

Case 2 - multi-sample VCF

Population- or biobank-scale VCFs most likely come in multi-sample format. The PharmCAT VCF Preprocessor is designed to help the users with this case and produce multiple single-sample VCFs that PharmCAT requires. The simplest command to preprocess a multi-sample VCF is as follows.

On the command line:

$ python3 pharmcat_vcf_preprocessor.py -vcf <multi_sample_vcf>

Sample script:

python3 pharmcat_vcf_preprocessor.py -vcf data/PharmCAT_tutorial_get-rm_wgs_30x_grch38.vcf.bgz

Case 3 - multi-sample VCF divided by chromosome or into consecutive genetic blocks

As sometimes seen with large-scale genetic studies, the genetic data may be divided into multiple by-chromosome VCFs or VCFs with consecutive genetic blocks. The PharmCAT VCF Preprocessor can manage this type of genetic data sets by taking a list of VCFs as the input.

On the command line:

$ python3 pharmcat_vcf_preprocessor.py -vcf <list_of_input_vcf>

Sample script:

# run the PharmCAT VCF Preprocessor for multiple VCFs with non-overlapping genetic regions of the same cohort
python3 pharmcat_vcf_preprocessor.py -vcf data/input_vcf_list.txt

Running PharmCAT

After running the PharmCAT VCF Preprocessor you should have multiple single-sample VCFs named like <base_filename>.<sample_id>.preprocessed.vcf.

Use the following command to batch annotate multiple VCFs using PharmCAT.

On the command line:

$ java -jar <path_to_the_latest_pharmcat_jar> -vcf <single_sample_vcf>

Sample script:

# running multiple samples
for SINGLE_SAMPLE in $(cat data/test_get-rm_samples.txt)
do
  # always use the latest PharmCAT
  java -jar pharmcat.jar -vcf results/pharmcat_ready/${SINGLE_SAMPLE}.preprocessed.vcf
done

The output is a set of PGx reports in HTML format named as pharmcat.<sample_id>.report.html.

Batch outside calls

To incorporate outside PGx calls with PharmCAT for multiple samples, the users have to prepare the outside PGx calls of each sample in separate files and supply the individual file as outside calls to the PharmCAT.

Running individual components

You can run the individual modules of PharmCAT on multiple samples in a similar manner to how you run the whole PharmCAT pipeline. This is useful if you are interested in understanding population PGx and specifically obtaining PGx frequencies (named alleles, diplotypes, or metabolizer phenotypes) in your cohort. To do so, you can run the following commands against your data.

Named Allele Matcher

On the command line:

$ java -jar <path_to_the_latest_pharmcat_jar> -matcher -vcf <sample.vcf>

Sample script:

for SINGLE_SAMPLE in "$(cat data/test_get-rm_samples.txt)"
do
  java -jar pharmcat.jar -matcher -vcf results/pharmcat_ready/${SINGLE_SAMPLE}.preprocessed.vcf
done

Phenotyper - use the Named Allele Matcher JSON data

On the command line:

$ java -jar <path_to_the_latest_pharmcat_jar> -phenotyper -pi <sample.match.json>

Sample script:

for SINGLE_SAMPLE in "$(cat data/test_get-rm_samples.txt)"
do
  java -jar pharmcat.jar -phenotyper -pi results/pharmcat_ready/${SINGLE_SAMPLE}.preprocessed.match.json
done

Reporter

On the command line:

$ java -jar <path_to_the_latest_pharmcat_jar> -reporter -ri <sample.phenotype.json> -reporterJson

Sample script:

for SINGLE_SAMPLE in "$(cat <sample_list.txt>)"
do
  java -jar pharmcat.jar -reporter -ri ${SINGLE_SAMPLE}.preprocessed.phenotype.json -reporterJson \
    -t "Report for ${SINGLE_SAMPLE}"
done

These commands yield Named Allele Matcher, Phenotyper, and Reporter results for each individual separately in the format of JSON files. We encourage the users to explore and perform data analysis using the rich content in these JSON files, which can be easily achieved using auxiliary JSON libraries and data analysis packages in R or python.

Extracting PharmCAT JSON content into TSV

We also provide an accessory python script under src/scripts/json2tsv/ that extracts and organizes the content from the PharmCAT JSON outputs into a tab-separated values (TSV) file. Here is an example TSV that the users will obtain from the provided Python script.

Sample Gene Phenotype Activity_Score Diplotype* DPYD_RYR1_Variants DPYD_RYR1_Variant_Functions DPYD_RYR1_Variant_Genotypes Haplotype_1 Haplotype_2 Haplotype_1_Functions Haplotype_2_Functions Haplotype_1_Variants Haplotype_2_Variants Missing_Positions Uncallable_Haplotypes
sample_1 ABCG2     rs2231142 reference (G)/rs2231142 reference (G)       rs2231142 reference (G) rs2231142 reference (G)            
sample_1 CYP3A5     *1/*1       *1 *1         99660516;99676198  
sample_1 SLCO1B1 Decreased Function   *1/*15       *1 *15 Normal function No function   21178615:C 21176804 *37
sample_1 CYP2C9 Normal Metabolizer 2.0         *1 *1 Normal function Normal function        
sample_1 RYR1 Uncertain Susceptibility   c.13513G>C (heterozygous) Reference;c.13513G>C Normal function;Normal function 38566986:C             38433867;38440747;38440796;<…truncated for visual clarity…> c.12115A>T;c.6349G>C;c.178G>T;<…truncated for visual clarity…>

[*] This column only shows the effectively phased DPYD and RYR1 diplotypes. If the column is empty, please check out other designated columns for DPYD or RYR1 variants.

Example command 

# the yaml file is under the PharmCAT/src/scripts/ folder
conda env create -f pharmcat_scripts.yaml
conda activate pharmcat_scripts
# extract json content into a tsv file
python3 json2tsv_pharmcat.py \
  -i </path/to/PharmCAT/output/folder/> \
  -a </path/to/pharmcat/allele/definition/json/*_translation.json> \
  -g CYP2C19,DPYD \
  -S <sample.txt> \
  -c -cp 4 \
  -o </results/>
Mandatory argument:
-i <path/to/PharmCAT/output/folder/>
Path to the directory that contains the PharmCAT Named Allele Matcher and Phenotyper JSON outputs.
Optional arguments:
-a </path/to/*_translation.json>
Path to the PharmCAT allele definition JSON files. Directory path should be included. Pattern matching is acceptable to read more than one sample.
-G gene1,gene2
A list of genes separated by comma. The script will only process results for these genes.
-S <txt_file>
A file of samples. One sample per line. The script will only process results for samples listed in this file.
-c
Enable concurrent mode.
-cp <num processes>
The maximum number of processes to use if concurrent mode is enabled.

Example with the Penn Medicine Biobank

This section provides an alternative example which is carried out on the Penn Medicine Biobank data. This example provides scripts that convert PharmCAT JSON files into a Python DataFrame and CSV/TSV

The Stanford and UPenn PharmCAT teams independently developed methods for post-processing multiple samples from PharmCAT. This method, developed by UPenn, takes the output JSON files from multiple PharmCAT runs and converts them to a DataFrame object for use in Python or export to CSV/TSV.

Preprocessing the data

Before proceeding, you should preprocess your multi-sample VCF or single sample VCFs using PharmCAT's VCF Preprocessor.

Running PharmCAT

Running PharmCAT on the single-sample VCFs is pretty straightforward. First you need to create a text file with all of all the output file names from the preprocessor. This can easily be generated with the command:

$ ls <preprocess_out_dir> | grep ".vcf$" > pharmcat_inputs.txt`

Verify that this contains all the samples by taking the line count (wc -l pharmcat_inputs.txt) and ensuring it equals the number of samples.

Then you need to use a for-loop to run PharmCAT repeatedly on each input file. The -reporterJson flag ensures that PharmCAT outputs JSON files for each sample containing the calls.

BASE_DIR="~/project/preprocess_out"  # the output directory from the preprocessor
OUT_DIR="pharmcat_out/"  # where to put the PharmCAT output
for i in $(cat pharmcat_inputs.txt) # a file with the filenames of your preprocessed VCFs
do
    SAMPLE=`echo  $i | cut -d "." -f 2` # the sample name is in the preprocessor output filename
    # always use the latest version of PharmCAT
    java -jar pharmcat.jar -vcf ${BASE_DIR}/${i} -bf ${SAMPLE} -reporterJson -o ${OUT_DIR}
done

Reading the PharmCAT calls into Python

Here is a exemplary python output for the PharmCAT Named Allele Matcher:

SAMPLE_ID CACNA1S CFTR CYP2B6 CYP2C19 rs12777823 CYP2C9 <…truncated for visual clarity…>
SAMPLE_1 Reference/Reference No CPIC variants found *1/*1 *1/*1 G/G *1/*1 <…truncated for visual clarity…>
SAMPLE_2 Reference/Reference No CPIC variants found *1/*1 *1/*1 G/G *1/*1 <…truncated for visual clarity…>
SAMPLE_3 Reference/Reference No CPIC variants found *1/*1 *1/*1 G/G *1/*1 <…truncated for visual clarity…>

Below is Python3 code for converting the report JSON files into Pandas DataFrames, which can be exported to CSV or processed further in python. Because of the long runtime of this process, we recommend saving the calls to CSV and loading the data from CSV when needed, instead of regenerating the DataFrames many times.

# Need to give a list of sample IDs
sample_list = [x.strip() for x in open("sample_ids.txt", "r").readlines()]
# PharmCAT output directory
base_dir = "~/project/pharmcat_out/"

# The following list specifies which genes should be pulled from the PharmCAT output. Be sure to include any new genes that get added to PharmCAT if they are relevant to you.
genelist = ["CACNA1S","CFTR","CYP2B6","CYP2C19","rs12777823","CYP2C9","CYP3A5","CYP4F2","DPYD","IFNL3/4","NUDT15","RYR1","TPMT","UGT1A1","VKORC1","SLCO1B1"]
columns = ["PID"] + genelist


for pid in sample_list:
    pid = str(pid)
    # Load in the JSON
    sample_file = "{0}/{1}.report.json".format(base_dir, pid.strip())
    sample_json = json.load(open(sample_file, "r"))

    # Build a dictionary that stores the genotype and phenotype for each gene from the JSON
    gene2genotype = dict([(key, "NA") for key in genelist])
    gene2phenotype = dict([(key, "NA") for key in genelist])
    for genotype in sample_json["genotypes"]:
        gene = genotype["gene"]
        # since there can be multiple genotypes called due to ambiguity, join them with ';'
        gene2genotype[gene] = ";".join(set(genotype["calls"]))
        gene2phenotype[gene] = ";".join(set(genotype["phenotype"]))

    # Optional section: code to extract rs12777823 for Warfarin (remove rs12777823 from genelist if deleting this section)
    for call in sample_json["geneCalls"]:
        if call["gene"] == "CYP2C9":
            for variant in call["variantsOfInterest"]:
                if variant["dbSnpId"] == "rs12777823":
                    gene2genotype["rs12777823"] = variant['call']
                    if gene2genotype["rs12777823"] is None:
                        gene2genotype["rs12777823"] = "NA"
                    gene2genotype["rs12777823"] = gene2genotype["rs12777823"].replace("|", "/")

    # Convert the dictionaries into DataFrames
	genotypes = pd.DataFrame(columns=columns)
	phenotypes = pd.DataFrame(columns=columns)
    ## Convert the dictionary into lists corresponding to DataFrame rows (one per sample)
    geno_row = [pid.strip()] + [gene2genotype[gene] for gene in gene2genotype]
    pheno_row = [pid.strip()] + [gene2phenotype[gene] for gene in gene2phenotype]

    ## Add each row to the DataFrames
    genotypes = genotypes.append(pd.Series(geno_row, index=genotypes.columns), ignore_index=True)
    phenotypes = phenotypes.append(pd.Series(pheno_row, index=phenotypes.columns), ignore_index=True)

    # Optional section: re-encode phenotypes from Warfarin-related genes
    phenotypes["CYP4F2"] = genotypes["CYP4F2"].apply(lambda x: "*3" in x).replace({False:"not actionable", True:"actionable"})
    phenotypes["VKORC1"] = genotypes["VKORC1"].apply(lambda x: "variant" in x).replace({False:"not actionable", True:"actionable"})
    phenotypes["IFNL3/4"] = genotypes["IFNL3/4"].apply(lambda x: "variant" in x).replace({False:"not actionable", True:"actionable"})
    phenotypes["rs12777823"] = genotypes["rs12777823"].apply(lambda x: "A" in x).replace({False:"not actionable", True:"actionable"})

genotypes = genotypes.set_index("PID")
phenotypes = phenotypes.set_index("PID")

# Output the DataFrames as CSV
genotypes.to_csv("genotypes.csv")
phenotypes.to_csv("phenotypes.csv")

The genotypes and phenotypes DataFrames should have the sample ID as the index, with one sample per row and one gene per column.

Reference

  1. Pratt, V. M. et al. Characterization of 137 Genomic DNA Reference Materials for 28 Pharmacogenetic Genes: A GeT-RM Collaborative Project. J Mol Diagn 18, 109–123 (2016).
  2. Byrska-Bishop, M. et al. High coverage whole genome sequencing of the expanded 1000 Genomes Project cohort including 602 trios. 2021.02.06.430068 (2021) doi:10.1101/2021.02.06.430068.
PharmCAT is managed at Stanford University & University of Pennsylvania (NHGRI U24HG013077).