iz {zlog}

Calculate Laboratory Measurements from z/zlog Values

Description

Inverse function to z or z(log) for laboratory measurement standardisation as proposed in Hoffmann 2017 et al.

Usage

iz(x, limits, probs = c(0.025, 0.975))

izlog(x, limits, probs = c(0.025, 0.975))

Arguments

x

numeric, z/zlog values.

limits

numeric or matrix, lower and upper reference limits. Has to be of length 2 for numeric or a two-column matrix with as many rows as elements in x.

probs

numeric, probabilities of the lower and upper reference limit, default: c(0.025, 0.975) (spanning 95 %). Has to be of length 2 for numeric or a two-column matrix with as many rows as elements in x.

Details

The inverse z value is calculated as follows (assuming that the limits where 0.025 and 0.975 quantiles): x = z * (limits_2 - limits_1)/3.92 + (limits_1 + limits_2)/2

The inverse z(log) value is calculated as follows (assuming that the limits where 0.025 and 0.975 quantiles): x = \exp(z * (\log(limits_2) - \log(limits_1))/3.92 + (\log(limits_1) + \log(limits_2))/2)

Value

numeric, laboratory measurements.

Author(s)

Sebastian Gibb

References

Georg Hoffmann, Frank Klawonn, Ralf Lichtinghagen, and Matthias Orth. 2017. "The Zlog-Value as Basis for the Standardization of Laboratory Results." LaboratoriumsMedizin 41 (1): 23–32. doi:10.1515/labmed-2016-0087.

See Also

zlog()

Examples

iz(z(1:10, limits = c(2, 8)), limits = c(2, 8))

# from Hoffmann et al. 2017
albuminzlog <- c(-0.15, -2.25, -1.15, 0.08, 1.57, -0.15, -4.53, -3.16, -5.70)
izlog(albuminzlog, limits = c(35, 52))

bilirubinzlog <- c(0.85, 0.57, -1.96, -0.43, 2.04, 3.12, 2.90, 5.72, 1.88)

limits <- cbind(
    lower = rep(c(35, 2), c(length(albuminzlog), length(bilirubinzlog))),
    upper = rep(c(52, 21), c(length(albuminzlog), length(bilirubinzlog)))
)
izlog(c(albuminzlog, bilirubinzlog), limits = limits)