rspiro (version 0.4)

zscore_NHANES3: Convert spirometric values to z-scores using NHANES III equations

Description

This function takes absolute spirometry measurements (FEV1, FVC, etc) in lt plus demographic data (age, height, gender and ethnicity) and converts them to z-scores based on the NHANES III equations.

Usage

zscore_NHANES3(
  age,
  height,
  gender = 1,
  ethnicity = 1,
  FEV1 = NULL,
  FVC = NULL,
  FEV1FVC = NULL,
  PEF = NULL,
  FEF2575 = NULL,
  FEV6 = NULL,
  FEV1FEV6 = NULL
)

Value

If only one spirometry argument is supplied, the function returns a numeric vector. If more are supplied, the function returns a data.frame with the same number of columns.

Arguments

age

Age in years

height

Height in meters

gender

Gender (1 = male, 2 = female) or a factor with two levels (first = male). Default is 1.

ethnicity

Ethnicity (1 = Caucasian, 2 = African-American, 3 = Mexican-American). Default is 1.

FEV1

Forced Expiratory Volume in 1 second (lt)

FVC

Forced Vital Capacity (lt)

FEV1FVC

FEV1 / FVC ratio

PEF

Peak Expiratory Flow (lt)

FEF2575

Forced Expiratory Flow between 25% and 75% of FVC (lt/s)

FEV6

Forced Expiratory Volume in 6 seconds (lt)

FEV1FEV6

FEV1 / FEV6 ratio

Details

At least one of the spirometric measurement arguments must be set (i.e. be non-NULL). Arguments age, height, gender and ethnicity must be vectors of length equal to the length of the spirometric measurement vector(s), or of length one, in which case their value is recycled. If any input vector is not of equal length, the function stops with an error.

Normal distributions are assumed for all parameters, even though per the NHANES III equations paper (Hankinson et al) this was observed only for FEV1, FVC, PEF and FEV6.

Examples

# Random data, 4 patients, one parameter supplied (FEV1)
zscore_NHANES3(age=seq(25,40,4), height=c(1.8, 1.9, 1.75, 1.85),
      gender=c(2,1,2,1), ethnicity=rep(1,4), FEV1=c(3.5, 4, 3.6, 3.9))