TABLE 2.

Parameter estimation of system-specific model and reference model with final model-associated bootstraps^a

Parameter	System-specific model					Reference model
	Final model		Final bootstrap			Final model		Final bootstrap
	Estimate	CV (%)	Estimateb	CI (2.5%)	CI (97.5%)	Estimate	CV (%)	Estimateb	CI (2.5%)	CI (97.5%)
OFV	−278.3					−305.3
CLc (liter/h/70 kg)	5.33	8	5.31	4.60	6.21	6.69	9	6.53	5.34	7.87
θCL_PNA	0.22 (FIX)					0.37	22	0.35	0.18	0.52
θCL_TEMP	2.43 (FIX)					2.58	26	2.82	1.01	4.71
θCL_GA	3.86 (FIX)					5.83	23	6.34	3.32	10.09
θUO	0.08 (FIX)
θCL_MOF						0.61	12	0.61	0.44	0.78
Vcc (liters/70 kg)	43.6	12	43.5	31.6	56.1	41.6	8	42.4	36.4	51.7
Q (liters/h/70 kg)	0.89	20	0.94	0.45	6.17	0.97	20	1.04	0.52	1.67
Vp (liters/70 kg)	32	26	31.3	11.4	57.6	70.9	37	69.9	15.4	828.2
Additive error	0.33	9	0.32	0.26	0.38	0.34	8	0.32	0.27	0.37
IIV CL (%)	49	11	48	36	61	45	15	43	28	61
IIV Vc (%)	53	29	52	15	92	22	39	24	5	48

^aOFV, objective function value; CL, clearance; PNA, postnatal age (days); TEMP, body temperature (°C); UO, urine output (ml/kg/h); GA, gestational age (days); MOF, multiorgan failure; CV, coefficient of variation; CI, confidence interval; V_c, volume of distribution of the central compartment; Q, intercompartmental clearance; V_p, volume of distribution of the peripheral compartment; IIV, interindividual variability; TV, typical value; BW, birthweight; FIX, fixed. The final system-specific model included the following equations: TVCL = 5.33 × (BW/70)^0.75 × (PNA/2.35)^0.22 × (TEMP/33.5)^2.43 × (UO/2.99)^0.08 × (GA/280)^3.86, TVVc = 43.6 × (BW/70)¹, TVQ = 0.89 × (BW/70)^0.75, and TVVp = 32 × (BW/70)¹. The final reference model included the following equations: TVCL = 6.69 × (BW/70)^0.75 × (PNA/2.21)^0.37 × (TEMP/33.5)^2.58 × 0.61^MOF × (GA/281)^5.83, TVVc = 41.6 × (BW/70)¹, TVQ = 0.97 × (BW/70)^0.75, and TVVp = 70.9 × (BW/70)¹.

^bMedian estimates.

^cCL and V_c were correlated for the system-specific model (r = 0.41) and the reference model (r = 0.84).