Adds a Parameter for BSA (Body Surface Area) Using the Specified Method

Adds a record for BSA (Body Surface Area) using the specified derivation method for each by group (e.g., subject and visit) where the source parameters are available.

Note: This is a wrapper function for the more generic derive_param_computed().

derive_param_bsa(
  dataset,
  by_vars,
  method,
  set_values_to = exprs(PARAMCD = "BSA"),
  height_code = "HEIGHT",
  weight_code = "WEIGHT",
  get_unit_expr,
  filter = NULL,
  constant_by_vars = NULL
)

Arguments

dataset

Input dataset

The variables specified by the by_vars argument are expected to be in the dataset. PARAMCD, and AVAL are expected as well.

The variable specified by by_vars and PARAMCD must be a unique key of the input dataset after restricting it by the filter condition (filter parameter) and to the parameters specified by HEIGHT and WEIGHT.

Default value

none

by_vars

Grouping variables

For each group defined by by_vars an observation is added to the output dataset. Only variables specified in by_vars will be populated in the newly created records.

Permitted values

list of variables created by exprs(), e.g., exprs(USUBJID, VISIT)

Default value

none

method

Derivation method to use. Note that HEIGHT is expected in cm and WEIGHT is expected in kg:

Mosteller: sqrt(height * weight / 3600)

DuBois-DuBois: 0.20247 * (height/100) ^ 0.725 * weight ^ 0.425

Haycock: 0.024265 * height ^ 0.3964 * weight ^ 0.5378

Gehan-George: 0.0235 * height ^ 0.42246 * weight ^ 0.51456

Boyd: 0.0003207 * (height ^ 0.3) * (1000 * weight) ^ (0.7285 - (0.0188 * log10(1000 * weight)))

Fujimoto: 0.008883 * height ^ 0.663 * weight ^ 0.444

Takahira: 0.007241 * height ^ 0.725 * weight ^ 0.425

Permitted values

character value

Default value

none

set_values_to

Variables to be set

The specified variables are set to the specified values for the new observations. For example exprs(PARAMCD = "MAP") defines the parameter code for the new parameter.

Permitted values

List of variable-value pairs

Default value

exprs(PARAMCD = "MAP")

height_code

HEIGHT parameter code

The observations where PARAMCD equals the specified value are considered as the HEIGHT assessments. It is expected that HEIGHT is measured in cm.

Permitted values

character value

Default value

"HEIGHT"

weight_code

WEIGHT parameter code

The observations where PARAMCD equals the specified value are considered as the WEIGHT assessments. It is expected that WEIGHT is measured in kg.

Permitted values

character value

Default value

"WEIGHT"

get_unit_expr

An expression providing the unit of the parameter

The result is used to check the units of the input parameters.

Permitted values

An expression which is evaluable in the input dataset and results in a character value

Default value

none

filter

Filter condition

The specified condition is applied to the input dataset before deriving the new parameter, i.e., only observations fulfilling the condition are taken into account.

Permitted values

an unquoted condition, e.g., AVISIT == "BASELINE"

Default value

NULL

constant_by_vars

By variables for when HEIGHT is constant

When HEIGHT is constant, the HEIGHT parameters (measured only once) are merged to the other parameters using the specified variables.

If height is constant (e.g. only measured once at screening or baseline) then use constant_by_vars to select the subject-level variable to merge on (e.g. USUBJID). This will produce BSA at all visits where weight is measured. Otherwise it will only be calculated at visits with both height and weight collected.

Default value

NULL

Value

The input dataset with the new parameter added. Note, a variable will only be populated in the new parameter rows if it is specified in by_vars.

See also

compute_bsa()

BDS-Findings Functions for adding Parameters/Records: default_qtc_paramcd(), derive_expected_records(), derive_extreme_event(), derive_extreme_records(), derive_locf_records(), derive_param_bmi(), derive_param_computed(), derive_param_doseint(), derive_param_exist_flag(), derive_param_exposure(), derive_param_framingham(), derive_param_map(), derive_param_qtc(), derive_param_rr(), derive_param_wbc_abs(), derive_summary_records()

Examples

library(tibble)

# Example 1: Derive BSA where height is measured only once using constant_by_vars
advs <- tibble::tribble(
  ~USUBJID, ~PARAMCD, ~PARAM, ~AVAL, ~VISIT,
  "01-701-1015", "HEIGHT", "Height (cm)", 170, "BASELINE",
  "01-701-1015", "WEIGHT", "Weight (kg)", 75, "BASELINE",
  "01-701-1015", "WEIGHT", "Weight (kg)", 78, "MONTH 1",
  "01-701-1015", "WEIGHT", "Weight (kg)", 80, "MONTH 2",
  "01-701-1028", "HEIGHT", "Height (cm)", 185, "BASELINE",
  "01-701-1028", "WEIGHT", "Weight (kg)", 90, "BASELINE",
  "01-701-1028", "WEIGHT", "Weight (kg)", 88, "MONTH 1",
  "01-701-1028", "WEIGHT", "Weight (kg)", 85, "MONTH 2",
)

derive_param_bsa(
  advs,
  by_vars = exprs(USUBJID, VISIT),
  method = "Mosteller",
  set_values_to = exprs(
    PARAMCD = "BSA",
    PARAM = "Body Surface Area (m^2)"
  ),
  get_unit_expr = extract_unit(PARAM),
  constant_by_vars = exprs(USUBJID)
)
#> # A tibble: 14 × 5
#>    USUBJID     PARAMCD PARAM                     AVAL VISIT   
#>    <chr>       <chr>   <chr>                    <dbl> <chr>   
#>  1 01-701-1015 HEIGHT  Height (cm)             170    BASELINE
#>  2 01-701-1015 WEIGHT  Weight (kg)              75    BASELINE
#>  3 01-701-1015 WEIGHT  Weight (kg)              78    MONTH 1 
#>  4 01-701-1015 WEIGHT  Weight (kg)              80    MONTH 2 
#>  5 01-701-1028 HEIGHT  Height (cm)             185    BASELINE
#>  6 01-701-1028 WEIGHT  Weight (kg)              90    BASELINE
#>  7 01-701-1028 WEIGHT  Weight (kg)              88    MONTH 1 
#>  8 01-701-1028 WEIGHT  Weight (kg)              85    MONTH 2 
#>  9 01-701-1015 BSA     Body Surface Area (m^2)   1.88 BASELINE
#> 10 01-701-1015 BSA     Body Surface Area (m^2)   1.92 MONTH 1 
#> 11 01-701-1015 BSA     Body Surface Area (m^2)   1.94 MONTH 2 
#> 12 01-701-1028 BSA     Body Surface Area (m^2)   2.15 BASELINE
#> 13 01-701-1028 BSA     Body Surface Area (m^2)   2.13 MONTH 1 
#> 14 01-701-1028 BSA     Body Surface Area (m^2)   2.09 MONTH 2 

derive_param_bsa(
  advs,
  by_vars = exprs(USUBJID, VISIT),
  method = "Fujimoto",
  set_values_to = exprs(
    PARAMCD = "BSA",
    PARAM = "Body Surface Area (m^2)"
  ),
  get_unit_expr = extract_unit(PARAM),
  constant_by_vars = exprs(USUBJID)
)
#> # A tibble: 14 × 5
#>    USUBJID     PARAMCD PARAM                     AVAL VISIT   
#>    <chr>       <chr>   <chr>                    <dbl> <chr>   
#>  1 01-701-1015 HEIGHT  Height (cm)             170    BASELINE
#>  2 01-701-1015 WEIGHT  Weight (kg)              75    BASELINE
#>  3 01-701-1015 WEIGHT  Weight (kg)              78    MONTH 1 
#>  4 01-701-1015 WEIGHT  Weight (kg)              80    MONTH 2 
#>  5 01-701-1028 HEIGHT  Height (cm)             185    BASELINE
#>  6 01-701-1028 WEIGHT  Weight (kg)              90    BASELINE
#>  7 01-701-1028 WEIGHT  Weight (kg)              88    MONTH 1 
#>  8 01-701-1028 WEIGHT  Weight (kg)              85    MONTH 2 
#>  9 01-701-1015 BSA     Body Surface Area (m^2)   1.82 BASELINE
#> 10 01-701-1015 BSA     Body Surface Area (m^2)   1.85 MONTH 1 
#> 11 01-701-1015 BSA     Body Surface Area (m^2)   1.87 MONTH 2 
#> 12 01-701-1028 BSA     Body Surface Area (m^2)   2.09 BASELINE
#> 13 01-701-1028 BSA     Body Surface Area (m^2)   2.07 MONTH 1 
#> 14 01-701-1028 BSA     Body Surface Area (m^2)   2.03 MONTH 2 

# Example 2: Derive BSA where height is measured only once and keep only one record
# where both height and weight are measured.

derive_param_bsa(
  advs,
  by_vars = exprs(USUBJID, VISIT),
  method = "Mosteller",
  set_values_to = exprs(
    PARAMCD = "BSA",
    PARAM = "Body Surface Area (m^2)"
  ),
  get_unit_expr = extract_unit(PARAM)
)
#> # A tibble: 10 × 5
#>    USUBJID     PARAMCD PARAM                     AVAL VISIT   
#>    <chr>       <chr>   <chr>                    <dbl> <chr>   
#>  1 01-701-1015 HEIGHT  Height (cm)             170    BASELINE
#>  2 01-701-1015 WEIGHT  Weight (kg)              75    BASELINE
#>  3 01-701-1015 WEIGHT  Weight (kg)              78    MONTH 1 
#>  4 01-701-1015 WEIGHT  Weight (kg)              80    MONTH 2 
#>  5 01-701-1028 HEIGHT  Height (cm)             185    BASELINE
#>  6 01-701-1028 WEIGHT  Weight (kg)              90    BASELINE
#>  7 01-701-1028 WEIGHT  Weight (kg)              88    MONTH 1 
#>  8 01-701-1028 WEIGHT  Weight (kg)              85    MONTH 2 
#>  9 01-701-1015 BSA     Body Surface Area (m^2)   1.88 BASELINE
#> 10 01-701-1028 BSA     Body Surface Area (m^2)   2.15 BASELINE

# Example 3: Pediatric study where height and weight are measured multiple times
advs <- tibble::tribble(
  ~USUBJID, ~PARAMCD, ~PARAM, ~AVAL, ~VISIT,
  "01-101-1001", "HEIGHT", "Height (cm)", 47.1, "BASELINE",
  "01-101-1001", "HEIGHT", "Height (cm)", 59.1, "WEEK 12",
  "01-101-1001", "HEIGHT", "Height (cm)", 64.7, "WEEK 24",
  "01-101-1001", "HEIGHT", "Height (cm)", 68.2, "WEEK 48",
  "01-101-1001", "WEIGHT", "Weight (kg)", 2.6, "BASELINE",
  "01-101-1001", "WEIGHT", "Weight (kg)", 5.3, "WEEK 12",
  "01-101-1001", "WEIGHT", "Weight (kg)", 6.7, "WEEK 24",
  "01-101-1001", "WEIGHT", "Weight (kg)", 7.4, "WEEK 48",
)
derive_param_bsa(
  advs,
  by_vars = exprs(USUBJID, VISIT),
  method = "Mosteller",
  set_values_to = exprs(
    PARAMCD = "BSA",
    PARAM = "Body Surface Area (m^2)"
  ),
  get_unit_expr = extract_unit(PARAM)
)
#> # A tibble: 12 × 5
#>    USUBJID     PARAMCD PARAM                     AVAL VISIT   
#>    <chr>       <chr>   <chr>                    <dbl> <chr>   
#>  1 01-101-1001 HEIGHT  Height (cm)             47.1   BASELINE
#>  2 01-101-1001 HEIGHT  Height (cm)             59.1   WEEK 12 
#>  3 01-101-1001 HEIGHT  Height (cm)             64.7   WEEK 24 
#>  4 01-101-1001 HEIGHT  Height (cm)             68.2   WEEK 48 
#>  5 01-101-1001 WEIGHT  Weight (kg)              2.6   BASELINE
#>  6 01-101-1001 WEIGHT  Weight (kg)              5.3   WEEK 12 
#>  7 01-101-1001 WEIGHT  Weight (kg)              6.7   WEEK 24 
#>  8 01-101-1001 WEIGHT  Weight (kg)              7.4   WEEK 48 
#>  9 01-101-1001 BSA     Body Surface Area (m^2)  0.184 BASELINE
#> 10 01-101-1001 BSA     Body Surface Area (m^2)  0.295 WEEK 12 
#> 11 01-101-1001 BSA     Body Surface Area (m^2)  0.347 WEEK 24 
#> 12 01-101-1001 BSA     Body Surface Area (m^2)  0.374 WEEK 48