Effects of measurement error on estimating biological half-life.

S. P. Caudill, J. L. Pirkle, Joel E Michalek

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Direct computation of the observed biological half-life of a toxic compound in a person can lead to an undefined estimate when subsequent concentration measurements are greater than or equal to previous measurements. The likelihood of such an occurrence depends upon the length of time between measurements and the variance (intra-subject biological and inter-sample analytical) associated with the measurements. If the compound is lipophilic the subject's percentage of body fat at the times of measurement can also affect this likelihood. We present formulas for computing a model-predicted half-life estimate and its variance; and we derive expressions for the effect of sample size, measurement error, time between measurements, and any relevant covariates on the variability in model-predicted half-life estimates. We also use statistical modeling to estimate the probability of obtaining an undefined half-life estimate and to compute the expected number of undefined half-life estimates for a sample from a study population. Finally, we illustrate our methods using data from a study of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure among 36 members of Operation Ranch Hand, the Air Force unit responsible for the aerial spraying of Agent Orange in Vietnam.

Original languageEnglish (US)
Pages (from-to)463-476
Number of pages14
JournalJournal of Exposure Analysis and Environmental Epidemiology
Volume2
Issue number4
StatePublished - Oct 1992
Externally publishedYes

Fingerprint

Measurement errors
half life
Half-Life
Time measurement
Poisons
Spraying
Oils and fats
Vietnam
dioxin
Sample Size
Fats
fat
Adipose Tissue
Antennas
Hand
Air
effect
Population
modeling

ASJC Scopus subject areas

  • Environmental Science(all)
  • Environmental Chemistry
  • Health, Toxicology and Mutagenesis
  • Pollution
  • Public Health, Environmental and Occupational Health
  • Toxicology

Cite this

Effects of measurement error on estimating biological half-life. / Caudill, S. P.; Pirkle, J. L.; Michalek, Joel E.

In: Journal of Exposure Analysis and Environmental Epidemiology, Vol. 2, No. 4, 10.1992, p. 463-476.

Research output: Contribution to journalArticle

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