Table 2.

Parameter Estimates for the Final Best Model Describing the Kinetics of NAb

Parameter	Value	Standard Error	% Relative Standard Error
Fixed effects
N0	96.05	1.690	1.76
kel1	0.017	0.001	8.48
beta_kel1_Age*	0.020	0.002	9.27
kel2	0.111	0.008	7.63
kel3	0.071	0.007	9.16
Standard deviation of the random effects
omega_N0	0.016	0.002	12.8
omega_kel1	1.37	0.099	7.25
omega_kel2	0.98	0.067	6.86
omega_kel3	1.10	0.081	7.36
Correlations
corr_kel2_kel1	0.78	0.037	4.68
Error model parameters
b	0.043	0.001	2.79

*Indicates a statistically significant (P = 0.0037 < 0.05) contribution of “age” as a covariate to the first-phase elimination rate constant.

b = the proportional error term of the model residual variability; beta_kel1_Age = constant for the contribution of “age” on kel1; corr_kel2_kel1 = the correlation coefficient between kel1 and kel2; kel1 = elimination rate constant of the first trimester (zero to third month); kel2 = elimination rate constant of the second trimester (third to sixth month); kel3 = elimination rate constant of the third trimester (sixth to ninth month); NAbs = neutralizing antibodies; N0 = average initial NAbs value; omega = between-subject variability estimate for each parameter.