Selection of initial model input parameters is an important step during model development. Input parameters are typically chosen to represent characteristics of the entire population: transitional probabilities (initiation, cessation, quitting, switching) and health outcome (mortality and/or morbidity rates). The initial values of these parameters are typically estimated from sources representative of the population, such as complex probability-based surveys or census data.
Transitional Probabilities
Transition probabilities are typically chosen to represent characteristics of the population of interest (e.g. initiation, cessation, quitting, switching). Transition probabilities determine the rate at which the population changes with respect to time during the period of interest. For example, one might be interested in projecting the health impact of introducing a new tobacco product to the US population for a period of 50 years starting with the year 2000; transition probabilities govern transition between tobacco use behavior as well as health outcome during the projection period (50 years, in this example). The following figure shows different transition for a 2-products model developed by the FDA; each letter represents a transitional probability representing transitions from tobacco use behaviors over time.
The figure below illustrates transitional probabilities for a two-product model. Transition probabilities are estimated from population surveys and other sources, and they are typically tabulated by sex, age and race. In some models, these are constant during the entire simulation period, but they could also change over time.
Example
This is an example of an ADaM dataset designed to capture the reference data describing historical transitional probabilities. When there are two products in the TOBACCO PRODUCT CATEGORY there are 27 different possible transitions. In the example data below, STRTM4 captures the combination of tobacco products of interest for this particular set of probabilities and STRTM5 captures the status of product(s) of interest pre-transition. STRTM6 captures the transition type of the combination of usage at the point of probability and STRTM7 captures the status of product(s) of interest post-transition.
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RFTRANSP Dataset Metadata
| Dataset | Description | Class | Structure | Purpose | Keys | Location | Documentation |
|---|---|---|---|---|---|---|---|
| RFTRANSP | Reference Data for Transition Prob | REFERENCE DATA STRUCTURE | one record per input value | reference | STRTM1, STRM2, STRTM3, STRTM4 STRTM5 STRTM6 STRTM7 | rftransp.xpt | NA |
RFTRANSP Variable Metadata
| Variable Name | Variable Label | Type | Codelist/Controlled Terms | Core | Notes |
|---|---|---|---|---|---|
| STRTM1 | Stratum 1 | text | YEAR | Req | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the left-most column in this example |
STRVAL1 | Stratum 1 Value | text | Req | populate with the STRTM1 values in the source data (Age in this example) | |
| STRTM2 | Stratum 2 | text | AGE | Cond | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the first part of the second column concept in this example |
STRVAL2 | Stratum 2 Value | text | Cond | populate with the STRTM2 values in the source data (F in this example for displayed data) | |
| STRTM3 | Stratum 3 | text | SEX | Cond | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the second part of the second column concept in this example |
STRVAL3 | Stratum 3 Value | text | F | Cond | populate with the STRTM3 values in the source data (Transition Type in this example) |
| STRTM4 | Stratum 4 | text | TOBACCO PRODUCT CATEGORY | Cond | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the third part of the second column concept in this example |
STRVAL4 | Stratum 4 Value | text | CIGARETTE/CIGAR | Cond | populate with the STRTM4 values in the source data (Product in this example) |
| STRTM5 | Stratum 5 | text | TOBACCO PRODUCT USE STATUS PRE-TRANSITION | Cond | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the second part of the second column concept in this example |
STRVAL5 | Stratum 5 Value | text | CURRENT/CURRENT;CURRENT/FORMER;CURRENT/NEVER;FORMER/CURRENT;FORMER/FORMER;FORMER/NEVER;NEVER/CURRENT;NEVER/FORMER;NEVER/NEVER | Cond | populate with the STRTM5 values in the source data (Transition Type in this example) |
| STRTM6 | Stratum 6 | text | TOBACCO PRODUCT USE TRANSITION TYPE | Cond | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the second part of the second column concept in this example |
STRVAL6 | Stratum 6 Value | text | INITIATION;CESSATION;SWITCHING;RELAPSE | Cond | populate with the STRTM6 values in the source data (Transition Type in this example) |
| STRTM7 | Stratum 7 | text | TOBACCO PRODUCT USE STATUS POST-TRANSITION | Cond | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the second part of the second column concept in this example |
STRVAL7 | Stratum 7 Value | text | CURRENT/CURRENT;CURRENT/FORMER;CURRENT/NEVER;FORMER/CURRENT;FORMER/FORMER;FORMER/NEVER;NEVER/CURRENT;NEVER/FORMER | Cond | populate with the STRTM7 values in the source data (Transition Type in this example) |
| INPRM | Input Parameter | text | TRANSITION PROBABILITY | Req | populate with the concept describing the value in the cell being captured in the dataset. it may come from a spreadsheet tab name, a spreadsheet name, or any desired parameter indentifying value |
| INPRMVAL | Input Parameter Value | float | Req | populate with the cell value from the referenced data that is being described by the STRMVALy values | |
| INPRMU | Input Parameter Unit | text | RATIO / 10 PER 1000 | Perm | populate with the unit describing the cell values if appropriate |
Mortality Rates and Risks
Another type of input parameters are those related to risk; this included mortality rates and risks related to comorbidities. For many models, these are projected over the entire simulation period (e.g., 50 years in the future), and they are estimated from population surveys or other data sources. These parameters are tabulated based on age, sex, race, tobacco use status, and years of tobacco use and/or former use.
Example
This is an example of an ADaM dataset designed to capture the reference data describing mortality rates.
RFMORT Dataset Metadata
| Dataset | Description | Class | Structure | Purpose | Keys | Location | Documentation |
|---|---|---|---|---|---|---|---|
| RFMORT | Reference Data for Mortality Rates | REFERENCE DATA STRUCTURE | one record per input value | reference | STRTM1, STRM2, STRTM3, STRTM4, STRTM5 | rfmort.xpt | NA |
RFMORT Variable Metadata
| Variable Name | Variable Label | Type | Codelist/Controlled Terms | Core | Notes |
|---|---|---|---|---|---|
| STRTM1 | Stratum 1 | text | AGE | Req | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the left-most column in this example |
| STRVAL1 | Stratum 1 Value | integer | Req | populate with the STRTM1 values in the source data (Age in this example) | |
| STRTM2 | Stratum 2 | text | SEX | Req | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the second column in this example |
| STRVAL2 | Stratum 2 Value | text | M;F | Req | populate with the STRTM2 values in the source data (Sex in this example) |
| STRTM3 | Stratum 3 | text | RACE | Req | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the third column in this example |
| STRVAL3 | Stratum 3 Value | text | WHITE | Req | populate with the STRTM3 values in the source data (Race in this example) |
| STRTM4 | Stratum 4 | text | YEAR | Req | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the fourth column in this example |
| STRVAL4 | Stratum 4 Value | integer | Req | populate with the STRTM4 values in the source data (Year in this example) | |
| STRTM5 | Stratum 5 | text | PRODUCT COMPARATORS | Req | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the fifth column in this example |
| STRVAL5 | Stratum 5 Value | text | DED1 | Req | populate with the STRTM5 values in the source data |
| INPRM | Input Parameter | text | MORTALITY PROBABILITY | Req | populate with the concept describing the value in the cell being captured in the dataset. it may come from a spreadsheet tab name, a spreadsheet name, or any desired parameter indentifying value |
| INPRMVAL | Input Parameter Value | float | Req | populate with the cell value from the referenced data that is being described by the STRMVALy values |
Birth Rate
At each step of the simulation period (e.g., each year), individuals may enter the population according to birth rates that are projected across the time horizon of the model. These rates are typically obtained from government census data.
Example
This is an example of an ADaM dataset designed to capture the reference data describing historical birth rates.
STRTMy captures the different stratum variables describing the content of a particular cell in the dataset. Stratum may be based on any combination of factors used to describe reference values (e.g., year in the birth rate data); sometimes these factors may be defined as compound factors (e.g., sex_race as sex and race in the birth rate source data). The y index for STRTMy does not indicate any particular ordering; the y value merely indicates a unique factor. If STRTMy concepts change across source data, the same STRTMy variable is still used (e.g., in the source data if a stratum changes from SEX to ETHNIC as the second stratum, then the same STRTM2 variable would be used and the value would change from Sex to Ethnic). The general assumption is that combinations of levels of granularity will be consistent across the source reference data. If that is not the case, then some of the STRTMy/STRMVALy variables may be null.
RFBR Dataset Metadata
| Dataset | Description | Class | Structure | Purpose | Keys | Location | Documentation |
|---|---|---|---|---|---|---|---|
| RFBR | Reference Data for Birthrate | REFERENCE DATA STRUCTURE | one record per input value | reference | STRTM1, STRM2, STRTM3 | rfbr.xpt | N/A |
RFBR Variable Metadata
| Variable Name | Variable Label | Type | Codelist/Controlled Terms | Core | Notes |
|---|---|---|---|---|---|
| STRTM1 | Stratum 1 | text | YEAR | Req | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the left-most column in this example |
STRVAL1 | Stratum 1 Value | text | Req | populate with the STRTM1 values in the source data (years 2000-2050 in this example) | |
| STRTM2 | Stratum 2 | text | SEX | Cond | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the first part of the second column concept in this example |
STRVAL2 | Stratum 2 Value | text | M;F | Cond | populate with the STRTM2 values in the source data (M/F in this example for displayed data) |
| STRTM3 | Stratum 3 | text | RACE | Cond | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the second part of the second column concept in this example |
STRVAL3 | Stratum 3 Value | text | TOTAL;WHITE | Cond | populate with the STRTM3 values in the source data (Race in this example) |
| INPRM | Input Parameter | text | BIRTH RATE | Req | populate with the concept describing the value in the cell being captured in the dataset. it may come from a spreadsheet tab name, a spreadsheet name, or any desired parameter identifying value |
| INPRMVAL | Input Parameter Value | float | Req | populate with the cell value from the referenced data that is being described by the STRMVALy values | |
| INPRMU | Input Parameter Unit | text | RATIO / 10 PER 1000 | Perm | populate with the unit describing the cell values if appropriate |
| REFSRCE | Reference Data Source | text | Perm | populate with the file that is the source of the reference data (the same columns and rows will change over time so identifying the source allows for traceability) |
Similar to birth rates, at each step of the simulation period individuals may enter the population according to migration rates. Base migration rates are generally obtained from national census data and if necessary are projected across the simulation timeframe. Depending on specific modeling assumptions, immigration demographics define the sex, age, race/ethnicity, and prevalence of tobacco product use behavior (never, current, former dual use, polytobacco use) in the immigrating population at a particular period.
Example
This is an example of an ADaM dataset designed to capture the reference data describing historical migration rates.
RFMIGRAT Dataset Metadata
| Dataset | Description | Class | Structure | Purpose | Keys | Location | Documentation |
|---|---|---|---|---|---|---|---|
| RFMIGRAT | Reference Data for Migration Rates | REFERENCE DATA STRUCTURE | one record per input value | reference | STRTM1, STRM2, STRTM3 | rfmigrat.xpt | NA |
RFMIGRAT Variable Metadata
| Variable Name | Variable Label | Type | Codelist/Controlled Terms | Core | Notes |
|---|---|---|---|---|---|
| STRTM1 | Stratum 1 | text | YEAR | Req | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the left-most column in this example |
STRVAL1 | Stratum 1 Value | integer TOBA-133 - Getting issue details... STATUS | Req | populate with the STRTM1 values in the source data (Age in this example) | |
| STRTM2 | Stratum 2 | text | SEX | Cond | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the first part of the second column concept in this example |
STRVAL2 | Stratum 2 Value | text | M;F;TOTAL | Cond | populate with the STRTM2 values in the source data (F/M/Total in this example for displayed data) |
| STRTM3 | Stratum 3 | text | RACE | Cond | populate with the variable descriptor of one of the cell descriptors (either a row identifier or a column identifier) - the second part of the second column concept in this example |
STRVAL3 | Stratum 3 Value | text | TOTAL | Cond | populate with the STRTM3 values in the source data (Race in this example) |
| INPRM | Input Parameter | text | NET MIGRATION RATE | Req | populate with the concept describing the value in the cell being captured in the dataset. it may come from a spreadsheet tab name, a spreadsheet name, or any desired parameter indentifying value |
| INPRMVAL | Input Parameter Value | integer | Req | populate with the cell value from the referenced data that is being described by the STRMVALy values | |
| INPRMU | Input Parameter Unit | text | COUNT | Perm | populate with the unit describing the cell values if appropriate |
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