The theoretical basis of the accuracy of a number of simple techniques for
estimating fractional zinc absorption (FZA) in humans using stable isotopic
tracers has not been evaluated. These techniques include fecal monitoring
(FM), deconvolution analysis (DA), double isotopic tracer ratio (DITR) and
indicator dilution methods. Using a compartmental model, we investigated th
e accuracy and logic of each of these techniques. Time-dependent estimates
of FZA based on the simple techniques were simulated using the compartmenta
l model and compared with the known FZA derived from the model. The analysi
s elucidated logical errors in some of the FM techniques, and even when the
se problems were corrected, the FM technique was still prone to errors due
to incomplete fecal tracer recovery and variable gastrointestinal (GI) tran
sit time. Although logically correct, the indicator dilution techniques wer
e also highly sensitive to incomplete fecal tracer recovery and variable GI
transit time. The DA and DITR techniques were the most robust in that they
were logically correct and were insensitive to incomplete fecal tracer rec
overy and variable GI transit time. Although all of the DA and DITR methods
provided similarly good estimates of FZA relative to the compartmental mod
el, the DITR technique performed on a spot urine specimen obtained several
days after tracer administration was the preferred choice because of its si
mplicity and minimal requirements for patient compliance.