Table 3.

Estimated effect of each additional month waiting to switch on CD4 T cell count 8 months later, based on observed history-adjusted parameter (Petersen et al. (2007a))

Term	Coefficient	95% CI
${\sum }_{j=t}^{t^{\ast }}a\left(j\right)$	-9.2	-17.6, -7.6
${\sum }_{j=t}^{t^{\ast }}a\left(j\right)\times \mathit{\text{CD}}4\left(t\right)$	0.05	0.02, 0.08
${\sum }_{j=t}^{t^{\ast }}a\left(j\right)\times t$	1.5	-0.4, 3.4
${\sum }_{j=t}^{t^{\ast }}a\left(j\right)\times t\times \mathit{\text{CD}}4\left(t\right)$	-0.009	-0.02, -0.004