TABLE 2.

Parameter estimates and bootstrap analysis of the published POPS TMP model and the external TMP model developed from the current study using the POPS and external data sets^a

Parameterb	POPS data		External data
	Parameter value (% RSE)c	Bootstrap analysis (n = 1,000), 2.5th–97.5th percentiles	Parameter value (% RSE)	Bootstrap analysis (n = 1,000), 2.5th–97.5th percentiles
Minimization successful	Yes	998/1,000	Yes	999/1,000
Fixed effects
Ka (h–1)	1.3 (36)	0.57–2.5	1.4 (21)	0.97–2.4
CL/F (liters/h)	11 (5.7)	9.3–12.0	9.8 (10)	7.9–13
V/F (liters)	150 (6.8)	130–170	125 (7.4)	110–150
PNA50 (yr)	0.24 (25)	0.13–0.41	0.91 (41)	0.35–2.7
SCR exponent	0.40 (20)	0.22–0.56	0.71 (25)	0.31–1.4
Random effects
IIV, CL/F (%)	34 (18)	12–48	31 (9.9)	22–36
IIV, V/F (%)	21 (45)	0.21–46	16 (45)	0.16–29
Proportional error (%)	51 (7.2)	43–58	19 (13)	14–24

^aThe Pediatric Opportunistic Pharmacokinetic Study (POPS) trimethoprim (TMP) model and the external TMP model have the same structural relationship: K_a (h^–1) = θ₁; $\text{CL/}F(\text{liters/h})={\theta }_2\times {(\text{WT/70})}^{0.75}\times [\text{PNA/(PNA \hspace{0.17em}}+{\theta }_3)]\times {(0.5\text{/SCR)}}^{-{\theta }_4}$; V/F (liters) = θ₅ × (WT/70), where θ is an estimated fixed effect, WT is the actual body weight in kilograms, and PNA is the postnatal age in years.

^bCL/F, apparent clearance; IIV, interindividual variability; K_a, absorption rate constant; PNA₅₀, maturation half-life calculated as a function of postnatal age (in years); SCR, serum creatinine; V/F, apparent volume of distribution.

^cRSE, relative standard error.