ESTIMATION OF RELATIVE BIOAVAILABILITY OF NUTRIENTS USING SAS PROCEDURES

The General Linear Models procedure (PROC: GLM) in SAS/STAT(R) softwar e can be programmed to perform the standard statistical analyses used for relative bioavailability studies. The first steps are validity che cks to test for statistical validity (linearity), fundamental validity (intersection of regression lines at 0 supplemental level), and equal ity of the basal diet mean to the point of intersection. The CLASS var iable capabilities of PROC GLM can be exploited to expedite these test s. After the validity checks, the GLM procedure can be used to obtain parameter estimates for calculation of relative bioavailability. Optio nal output provides an inverse matrix to calculate standard errors of slopes and slope ratios. Logarithmic and other transformations of the dependent variable to reduce variance heterogeneity or achieve lineari ty for subsequent calculation of appropriate bioavailability values al so can be accomplished within the SAS System. When nonlinear regressio n models are more appropriate than linear models, the NLIN procedure c an be used.