Table 2.

Selected Covariate Models Evaluated

Covariate model	Covariance CL, V	−2LL	Δ−2LL	Comment
None	Yes	−77.167		Base model
WT on V	No	−69.784	+7.383	Did not converge
WT on V	Yes	−73.998	+3.169	Did not converge, covariance term not estimable
WT on CL	No	−81.188	−4.021
WT on CL	Yes	−82.204	−5.037	Did not converge
LBW on CL and V	No	−83.288	−6.121
WT on CL and V	No	−84.218	−7.051	Final model
WT on CL and V	Yes	−84.469	−7.302	Covariance term implausible
CLcr on CLr 1	No	−87.277	−10.11	IIV CL not estimable (estimated at 1%, biologically implausible), covariance step aborted
CLcr on CLr 3	No	−87.803	−10.64	IIV CL not estimable, covariance step aborted
CLcr on CLr 2	No	−90.256	−13.09	Did not converge, IIV CL not estimable

Covariate models including WT or LBW had fixed allometric exponents; therefore, no degrees of freedom were added.

CL, clearance; CLcr, creatinine clearance; CLr, renal clearance; IIV, inter-individual variability; LBW, lean body weight; TBW, total body weight; V, volume of distribution; −2LL, objective function value; Δ−2LL, change in objective function value