Determination of fecal alpha 1-antitrypsin concentration by radial immunodiffusion: two systems compared.

We compared Helena "QUIPlates" and Calbiochem "LC-Partigen" radial immunodiffusion systems for their ability to measure fecal concentrations of alpha 1-antitrypsin (FA1AT). Reference ranges for FA1AT concentrations in infants receiving various diets, in children, and in adults are given for each system. FA1AT values obtained with Calbiochem LC-Partigen plates averaged 30% greater than those obtained with Helena QUIPlates, but both systems distinguished between normal and high values. Studies involving variations of usual sample-handling procedures showed that storage at room temperature, repeated freezing and thawing, and long-term storage of frozen samples had no significant effect on measured FA1AT concentration. However, values obtained for lyophilized and nonlyophilized samples did not correlate well.