Table 3.

Predictors of switching to second-line antiretroviral therapy

Variable	Sites with routine viral load monitoring (n=5058)		Sites without routine viral load monitoring (n=8699)		P for interaction*
	Adjusted HR (95% CI)	P-value	Adjusted HR (95% CI)	P-value
Age (years)		0.55		0.25	0.23
16–29	1		1
30–39	0.93 (0.62–1.39)		0.93 (0.62–1.39)
40–49	0.69 (0.41–1.17)		1.33 (0.84–2.12)
≥ 50	0.97 (0.47–1.98)		1.46 (0.73–2.91)
Sex		0.91		0.11	0.34
Male	1		1
Female	0.98 (0.68–1.41)		1.36 (0.94–1.98)
Time period of starting ART		0.001		0.06	0.53
< 2002	1		1
2002–2004	0.40 (0.25–0.65)		0.58 (0.32–1.03)
2005–2006	0.55 (0.29–1.06)		0.88 (0.45–1.72)
Baseline CD4 (cells/μl)		0.03		<0.001	0.87
< 25	4.81 (0.64–35.94)		6.21 (1.47–26.12)
25–49	3.59 (0.47–27.35)		5.12 (1.19–21.97)
50–99	3.13 (0.42–23.59)		4.01 (0.95–16.82)
100–199	2.35 (0.32–17.54)		2.55 (0.61–10.64)
200–349	2.03 (0.26–15.92)		1.50 (0.34–6.69)
≥ 350	1		1
Clinical stage		1.00		0.91	0.67
Less advanced	1		1
Advanced	1.00 (0.55–1.82)		1.02 (0.67–1.57)
Number of antiretroviral drugs available in programme		0.26		0.58	0.45
≤ 10	1		1
11–13	1.96 (0.36–10.82)		1.90 (0.47–7.73)
≥ 14	3.56 (0.78–16.34)		1.04 (0.22–5.05)

^*Test for interaction between sites with and without routine viral load monitoring