Table 2.

Parameter estimates of final creatinine model together with effect size estimates. CV, coefficient of variation; MOD, mode of delivery (1 for C-section and 0 for vaginal delivery); IBU, ibuprofen treatment (1 for yes and 0 for no treatment). Median GA was set at 26.73 weeks

Parameter (unit)	Estimates (RSE%)	IIV [CV%]
Population parameters
Creabirth (mg/dl)	0.597 (2.31)	0.252 [25.6]
Kinproduction (mg/day)	3.55 (1.44)	–
CLBL (L/day)	0.075 (3.95)	0.255 [25.9]
Emax (day−1)	0.874 (0.36)	–
t50 (days)	21.1 (8.72)	0.49 [52]
Hill	1.31 (4.79)	0.481 [51]
Covariate parameters		Parameter-covariate relationship
IBU effect on CLBL (no/yes)	2.73 (0.29) / 2.55 (0.61)	${\mathrm{CL}}_{{\mathrm{BL}}_i}={\mathrm{CL}}_{{\mathrm{BL}}_{\mathrm{pop}}}\times \left(1+2.73\right)/{\mathrm{CL}}_{{\mathrm{BL}}_{\mathrm{pop}}}\times \left(1+2.55\right)$
GA effect on t50	− 2.35 (36.3)	$t{50}_i=t{50}_{\mathrm{pop}}\times {\frac{{\mathrm{GA}}_i}{{\mathrm{GA}}_{\mathrm{m}}}}^{-2.35}\times \left(1-0.24\times \mathrm{MOD}\right)$
MOD effect on t50	− 0.24 (47)
GA effect on Creabirth	1.6 (21.6)	${\text{Crea}}_{{\text{birth}}_i}={\text{Crea}}_{{\text{birth}}_{\mathrm{pop}}}\times {\frac{{\mathrm{GA}}_i}{{\mathrm{GA}}_{\mathrm{m}}}}^{1.6}$
Residual variability
Proportional error	0.11 (1.5)	[11]