abstcal 0.5

Calculate abstinence using the timeline followback data in substance research

Abstinence Calculator

A Python package to calculate abstinence results using the timeline followback interview data

Installation

Install the package using the pip tool. If you need instruction on how to install Python, you can find information at the Python website. The pip tool is the most common Python package management tool, and you can find information about its use instruction at the pypa website.

If you're not familiar with Python coding, you can run the Jupyter Notebook included on this page on Google Colab, which is an online platform to run your Python code remotely on a server.

pip install abstcal

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Overview of the Package

This package is developed to score abstinence using the Timeline Followback (TLFB) and visit data in clinical substance use research. It provides functionalities to preprocess the datasets to remove duplicates and outliers. In addition, it can impute missing data using various criteria.

It supports the calculation of abstinence of varied definitions, including continuous, point-prevalence, and prolonged using either intent-to-treat (ITT) or responders-only assumption. It can optionally integrate biochemical verification data.

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Required Datasets

The Timeline Followback Data (Required)

The dataset should have three columns: id, date, and amount. The id column stores the subject ids, each of which should uniquely identify a study subject. The date column stores the dates when daily substance uses are collected. The amount column stores substance uses for each day.

id	date	amount
1000	02/03/2019	10
1000	02/04/2019	8
1000	02/05/2019	12
1000	02/06/2019	9
1000	02/07/2019	10
1000	02/08/2019	8

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The Biochemical Measures Dataset (Optional)

The dataset should have three columns: id, date, and amount. The id column stores the subject ids, each of which should uniquely identify a study subject. The date column stores the dates when daily substance uses are collected. The amount column stores the biochemical measures that verify substance use status.

id	date	amount
1000	02/03/2019	4
1000	02/11/2019	6
1000	03/04/2019	10
1000	03/22/2019	8
1000	03/28/2019	6
1000	04/15/2019	5

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The Visit Data (Required)

It needs to be in one of the following two formats. The long format. The dataset should have three columns: id, visit, and date. The id column stores the subject ids, each of which should uniquely identify a study subject. The visit column stores the visits. The date column stores the dates for the visits.

id	visit	date
1000	0	02/03/2019
1000	1	02/10/2019
1000	2	02/17/2019
1000	3	03/09/2019
1000	4	04/07/2019
1000	5	05/06/2019

The wide format. The dataset should have the id column and additional columns with each representing a visit.

id	v0	v1	v2	v3	v4	v5
1000	02/03/2019	02/10/2019	02/17/2019	03/09/2019	04/07/2019	05/06/2019
1001	02/05/2019	02/13/2019	02/20/2019	03/11/2019	04/06/2019	05/09/2019

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Supported Abstinence Definitions

The following abstinence definitions have both calculated as the intent-to-treat (ITT) or responders-only options. By default, the ITT option is used.

1. Continuous Abstinence: No substance use in the defined time window. Usually, it starts with the target quit date.
2. Point-Prevalence Abstinence: No substance use in the defined time window preceding the assessment time point.
3. Prolonged Abstinence Without Lapses: No substance use after the grace period (usually 2 weeks) until the assessment time point.
4. Prolonged Abstinence With Lapses: Lapses are allowed after the grace period until the assessment time point.

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Use Example

1. Import the Package

from abstcal import TLFBData, VisitData, AbstinenceCalculator

2. Process the TLFB Data

2a. Read the TLFB data

You can either specify the full path of the TLFB data or just the filename if the dataset is in your current work directory. Supported file formats include comma-separated (.csv), tab-delimited (.txt), and Excel spreadsheets (.xls, .xlsx).

tlfb_data = TLFBData('path_to_tlfb.csv')

2b. Profile the TLFB data

In this step, you will see a report of the data summary, such as the number of records, the number of subjects, and any applicable abnormal data records, including duplicates and outliers. In terms of outliers, you can specify the minimal and maximal values for the substance use amounts. Those values outside of the range are considered outliers and are shown in the summary report.

# No outlier identification
tlfb_data.profile_data()

# Identify outliers that are outside of the range
tlfb_data.profile_data(0, 100)

2c. Drop data records with any missing values

Those records with missing id, date, or amount will be removed. The number of removed records will be reported.

tlfb_data.drop_na_records()

2d. Check and remove any duplicate records

Duplicate records are identified based on id and date. There are different ways to remove duplicates: min, max, or mean, which keep the minimal, maximal, or mean of the duplicate records. You can also have the options to remove all duplicates. You can also simply view the duplicates and handle these duplicates manually.

# Check only, no actions for removing duplicates
tlfb_data.check_duplicates(None)

# Check and remove duplicates by keeping the minimal
tlfb_data.check_duplicates("min")

# Check and remove duplicates by keeping the maximal
tlfb_data.check_duplicates("max")

# Check and remove duplicates by keeping the computed mean (all originals will be removed)
tlfb_data.check_duplicates("mean")

# Check and remove all duplicates
tlfb_data.check_duplicates(False)

2e. Recode outliers (optional)

Those values outside the specified range are considered outliers. All these outliers will be removed by default. However, if the users set the drop_outliers argument to be False, the values lower than the minimal will be recoded as the minimal, while the values higher than the maximal will be recoded as the maximal.

In either case, the number of recoded outliers will be reported.

# Set the minimal and maximal values for outlier detection, by default, the outliers will be dropped
tlfb_data.recode_outliers(0, 100)

# Alternatively, we can recode outliers by replacing them with bounding values
tlfb_data.recode_outliers(0, 100, False)

2f. Impute the missing TLFB data

To calculate the ITT abstinence, the TLFB data will be imputed for the missing records. All contiguous missing intervals will be identified. Each of the intervals will be imputed based on the two values, the one before and the one after the interval.

You can choose to impute the missing values for the interval using the mean of these two values or interpolate the missing values for the interval using the linear values generated from the two values. Alternatively, you can specify a fixed value, which will be used to impute all missing values.

Other important parameters include last_record_action, which defines how you interpolate TLFB records using each subject's last record and maximum_allowed_gap_days, which defines the maximum allowed days for TLFB data imputation. When the missing interval is too large (e.g., 1 year), it's not realistic to interpolate the entire time window

It's also possible to integrate biochemical verification data with the TLFB imputation. The details are discussed later.

# Use the mean
tlfb_data.impute_data("uniform")

# Use the linear interpolation
tlfb_data.impute_data("linear")

# Use a fixed value, whichever is appropriate to your research question
tlfb_data.impute_data(1)
tlfb_data.impute_data(5)

3. Process the Visit Data

3a. Read the visit data

Similar to reading the TLFB data, you can read files in .csv, .txt, .xls, or .xlsx format. It's also supported if your visit dataset is in the univariate format, which means that each subject has only one row of data and the columns are the visits and their dates.

# Read the visit data in the long format (the default option)
visit_data = VisitData("file_path.csv")

# Read the visit data in the wide format
visit_data = VisitData("file_path.csv", "wide")

3b. Profile the visit data

You will see a report of the data summary, such as the number of records, the number of subjects, and any applicable abnormal data records, including duplicates and outliers. In terms of outliers, you can specify the minimal and maximal values for the dates. The dates will be inferred from strings. Please use the format mm/dd/yyyy.

Importantly, it will also detect if any subjects have their visits with the dates that are out of the order. By default, the order is inferred using the numeric or alphabetic order of the visits. These records with possibly incorrect data may result in wrong abstinence calculations.

# No outlier identification
visit_data.profile_data()

# Outlier identification
visit_data.profile_data("07/01/2000", "12/08/2020")

# Specify the expected order of the visits
visit_data.profile_data(expected_visit_order=[1, 2, 3, 5, 4])

3c. Drop data records with any missing values

Those records with missing id, visit, or date will be removed. The number of removed records will be reported.

visit_data.drop_na_records()

3d. Check and remove any duplicate records

Duplicate records are identified based on id and visit. There are different ways to remove duplicates: min, max, or mean, which keep the minimal, maximal, or mean of the duplicate records. The options are the same as how you deal with duplicates in the TLFB data.

# Check only, no actions for removing duplicates
visit_data.check_duplicates(None)

# Check and remove duplicates by keeping the minimal
visit_data.check_duplicates("min")

# Check and remove duplicates by keeping the maximal
visit_data.check_duplicates("max")

# Check and remove duplicates by keeping the computed mean (all originals will be removed)
visit_data.check_duplicates("mean")

# Check and remove all duplicates
visit_data.check_duplicates(False)

3e. Recode outliers (optional)

Those values outside the specified range are considered outliers. The syntax and usage is the same as what you deal with the TLFB dataset

# Set the minimal and maximal, and outliers will be removed by default
visit_data.recode_outliers("07/01/2000", "12/08/2020")

# Set the minimal and maximal, but keep the outliers by replacing them with bounding values
visit_data.recode_outliers("07/01/2000", "12/08/2020", False)

3f. Impute the missing visit data

To calculate the ITT abstinence, the visit data will be imputed for the missing records. The program will first find the earliest visit date as the anchor visit, which should be non-missing for all subjects. Then it will calculate the difference in days between the later visits and the anchor visit. Based on these difference values, the following two imputation options are available. The "freq" option will use the most frequent difference value, which is the default option. The "mean" option will use the mean difference value.

# Use the most frequent difference value between the missing visit and the anchor visit
visit_data.impute_data(impute="freq")

# Use the mean difference value between the missing visit and the anchor visit
visit_data.impute_data(impute="mean")

# Specify which visit should serve as the anchor or reference visit
visit_data.impute_data(anchor_visit=1)

4. Calculate Abstinence

4a. Create the abstinence calculator using the TLFB and visit data

To calculate abstinence, you instantiate the calculator by setting the TLFB and visit data. By default, only those who have both TLFB and visit data will be scored.

abst_cal = AbstinenceCalculator(tlfb_data, visit_data)

4b. Check data availability (optional)

You can find out how many subjects have the TLFB data and how many have the visit data.

abst_cal.check_data_availability()

4c. Calculate abstinence

For all the function calls to calculate abstinence, you can request the calculation to be ITT (intent-to-treat) or RO (responders-only). You can optionally specify the calculated abstinence variable names. By default, the abstinence names will be inferred. Another shared argument is whether you want to include the ending date. Notably, each method will generate the abstinence dataset and a dataset logging first lapses that make a subject nonabstinent for a particular abstinence calculation.

Continuous abstinence

To calculate the continuous abstinence, you need to specify the visit when the window starts and the visit when the window ends. To provide greater flexibility, you can specify a series of visits to generate multiple time windows.

# Calculate only one window
abst_df, lapse_df = abst_cal.abstinence_cont(2, 5)

# Calculate two windows
abst_df, lapse_df = abst_cal.abstinence_cont(2, [5, 6])

# Calculate three windows with abstinence names specified
abst_df, lapse_df = abst_cal.abstinence_cont(2, [5, 6, 7], ["abst_var1", "abst_var2", "abst_var3"])

Point-prevalence abstinence

To calculate the point-prevalence abstinence, you need to specify the visits. You'll need to specify the number of days preceding the time points. To provide greater flexibility, you can specify multiple visits and multiple numbers of days.

# Calculate only one time point, 7-d point-prevalence
abst_df, lapse_df = abst_cal.abstinence_pp(5, 7)

# Calculate multiple time points, multiple day conditions
abst_df, lapse_df = abst_cal.abstinence_pp([5, 6], [7, 14, 21, 28])

Prolonged abstinence

To calculate the prolonged abstinence, you need to specify the quit visit and the number of days for the grace period (the default length is 14 days). You can calculate abstinence for multiple time points. There are several options regarding how a lapse is defined. See below for some examples.

# Lapse isn't allowed
abst_df, lapse_df = abst_cal.abstinence_prolonged(3, [5, 6], False)

# Lapse is defined as exceeding a defined amount of substance use
abst_df, lapse_df = abst_cal.abstinence_prolonged(3, [5, 6], '5 cigs')

# Lapse is defined as exceeding a defined number of substance use days
abst_df, lapse_df = abst_cal.abstinence_prolonged(3, [5, 6], '3 days')

# Lapse is defined as exceeding a defined amount of substance use over a time window
abst_df, lapse_df = abst_cal.abstinence_prolonged(3, [5, 6], '5 cigs/7 days')

# Lapse is defined as exceeding a defined number of substance use days over a time window
abst_df, lapse_df = abst_cal.abstinence_prolonged(3, [5, 6], '3 days/7 days')

# Combination of these criteria
abst_df, lapse_df = abst_cal.abstinence_prolonged(3, [5, 6], ('5 cigs', '3 days/7 days'))

5. Output Datasets

5a. The abstinence datasets

To output the abstinence datasets that you have created from calling the abstinence calculation methods, you can use the following method to create a combined dataset, something like below.

id	itt_abst_cont_v5_v2	itt_abst_cont_v6_v2	itt_abst_pp7_v5	itt_abst_pp7_v6
1000	1	1	1	1
1001	1	0	1	0
1002	1	1	1	1
1003	0	0	1	1
1004	0	0	1	0
1005	0	0	0	1

abst_cal.merge_abst_data_to_file([abst_df0, abst_df1, abst_df2], "merged_abstinence_data.csv")

5b. The lapse datasets

To output the lapse datasets that you have created from calling the abstinence calculation methods, you can use the following method to create a combined dataset, something like below.

id	date	amount	abst_name
1000	02/03/2019	10	itt_abst_cont_v5
1001	03/05/2019	8	itt_abst_cont_v5
1002	04/06/2019	12	itt_abst_cont_v5
1000	02/06/2019	9	itt_abst_cont_v6
1001	04/07/2019	10	itt_abst_cont_v6
1002	05/08/2019	8	itt_abst_cont_v6

abst_cal.merge_lapse_data_to_file([lapse_df0, lapse_df1, lapse_df2], "merged_lapse_data.csv")

Additional Features

I. Integration of Biochemical Verification Data

If your study has collected biochemical verification data, such as carbon monoxide for smoking or breath alcohol concentration for alcohol intervention, these biochemical data can be integrated into the TLFB data. In this way, non-honest reporting can be identified (e.g., self-reported of no use, but biochemically un-verified), the self-reported value will be overridden, and the updated record will be used in later abstinence calculation.

The following code shows you a possible work flow. Please note that the biochemical measures dataset should have the same data structure as you TLFB dataset. In other words, it should have three columns: id, date, and amount.

Ia. Prepare the Biochemical Dataset

A key operation to prepare the biochemical dataset is to interpolate extra meaningful records based on the exiting records using the interpolate_biochemical_data function, as shown below.

# First read the biochemical verification data
biochemical_data = TLFBData("beam_co.csv", included_subjects=included_subjects, abst_cutoff=4)
biochemical_data.profile_data()

# Interpolate biochemical records based on the half-life
biochemical_data.interpolate_biochemical_data(0.5, 1)

# Other data cleaning steps
biochemical_data.drop_na_records()
biochemical_data.check_duplicates()

Ib. Integrate the Biochemical Dataset with the TLFB data

The following code shows you how the integration can be performed. Everything else stays the same, except that in the impute_data method, you need to specify the biochemical_data argument.

tlfb_data = TLFBData("beam_tlfb.csv", included_subjects=included_subjects)
tlfb_sample_summary, tlfb_subject_summary = tlfb_data.profile_data()
tlfb_data.drop_na_records()
tlfb_data.check_duplicates()
tlfb_data.recode_data()
tlfb_data.impute_data(biochemical_data=biochemical_data)

II. Calculate Retention Rates

You can also calculate the retention rate with the visit data with a simple function call, as shown below. If a filepath is specified, it will write to a file.

# Just show the retention rates results
visit_data.get_retention_rates()

# Write the retention rates to an external file
visit_data.get_retention_rates('retention_rates.csv')

III. Calculate Abstinence Rates

You can calculate the computed abstinence by providing the list of pandas DataFrame objects.

# Calculate abstinence by various definitions
abst_pp, lapses_pp = abst_cal.abstinence_pp([9, 10], 7, including_end=True)
abst_pros, lapses_pros = abst_cal.abstinence_prolonged(4, [9, 10], '5 cigs')
abst_prol, lapses_prol = abst_cal.abstinence_prolonged(4, [9, 10], False)

# Calculate abstinence rates for each
abst_cal.calculate_abstinence_rates([abst_pp, abst_pros, abst_prol])
abst_cal.calculate_abstinence_rates([abst_pp, abst_pros, abst_prol], 'abstinence_results.csv')

It will create the following DataFrame as the output. If a filepath is specified, it will write to a file.

Abstinence Name	Abstinence Rate
itt_pp7_v9	0.159091
itt_pp7_v10	0.170455
itt_prolonged_5_cigs_v9	0.159091
itt_prolonged_5_cigs_v10	0.113636
itt_prolonged_False_v9	0.102273
itt_prolonged_False_v10	0.068182

Questions or Comments

If you have any questions about this package, please feel free to leave comments here or send me an email to [e-mail].

License

MIT License