Table 2.

Results of Mixed-Effects Log-Linear Modeling of the Relative Incidence of Raised Viral Load (>1000 Copies/mL)

Variable	A			B
	IRR	(95% CI)	P Value	IRR	(95% CI)	P Value
Age, y
18–22	3.23	(1.57–6.63)	.001	3.67	(1.78–7.56)	<.001
23–25	2.48	(1.20–5.11)	.014	2.66	(1.31–5.41)	.007
26–29	1.91	(.97–3.77)	.061	2.18	(1.12–4.24)	.021
30–33	1.61	(.79–3.28)	.192	1.58	(.78–3.20)	.207
≥34	1.0	(reference)		1.0	(reference)
Gestation at ART initiation, wk
≤14	1.0	(reference)		1.0	(reference)
>14–28	1.48	(.80–2.76)	.212	1.35	(.72–2.52)	.346
>28	2.51	(1.29–4.91)	.007	2.21	(1.13–4.34)	.021
Previous ART
None	1.0	(reference)		1.0	(reference)
ZDV ± NVP (short course)	1.23	(.79–1.89)	.359	1.50	(.96–2.34)	.073
Triple-drug therapy	2.97	(1.30–6.81)	.010	2.94	(1.29–6.69)	.010
Pre-ART CD4 count, cells/µL
<200	1.0	(reference)		1.0	(reference)
200–350	0.72	(.42–1.24)	.239	0.90	(.51–1.59)	.791
350–500	0.80	(.45–1.42)	.448	0.88	(.48–1.60)	.673
>500	0.50	(.27–0.91)	.023	0.63	(.33–1.20)	.156
Pre-ART VL, copies/mL
<3.0 log10	1.0	(reference)		1.0	(reference)
3.0–4.0 log10	2.01	(.97–4.14)	.060	1.84	(.91–3.69)	.085
4.0–5.0 log10	2.00	(.96–1.15)	.062	1.44	(.69–3.00)	.333
>5.0 log10	4.00	(1.64–9.79)	.002	2.66	(1.09–6.45)	.031
Time from VL suppression to VL measurement, mo	1.13	(1.09–1.17)	<.001	1.11	(1.07–1.15)	<.001
Follow-up
Antenatal period	1.0	(reference)		1.0	(reference)
Postpartum period	7.83	(1.89–32.51)	.005	6.41	(1.54–26.69)	.011

“A” shows crude associations involving single variables adjusted only for time after initial viral suppression; “B” shows a single model including all covariates shown.

Abbreviations: ART, antiretroviral therapy; CI, confidence interval; IRR, incidence rate ratio; NVP, nevirapine; VL, viral load; ZDV, zidovudine.