Table 3. Relationship between baseline or time-varying characteristics and interval (days) between viral load measurements using crude mixed model analysis.

	Crude analysisa
Characteristics	Mean interval,daysb	Estimate, days (95% CI)	P
Gender
Female	152.1	−4.9 (−13.2, 3.5)	0.251
Male	157	0
Age, per 10 years	–	0.1 (−5.9, 6.2)	0.933
Mode of infection
MSM	146.2	−14.7 (−27.3, −2.2)	0.022
Non-MSM	160.9	0
Distance from HIV center
<160 km	144.8	−19.4 (−31.5, −7.3)	0.002
≥160 km	164.2	0
Migrant worker (seafarer)
No	151	−36.8 (−54.0, −19.6)	<0.001
Yes	187.8	0
Level of education
College/University	149.5	−9.0 (−22.0, 4.0)	0.173
High school and lower	158.5	0
Place of living
Rural	154.1	−1.9 (−15.1, 11.3)	0.776
Urban	156	0
Baseline CD4 cell count/µL, per 100 cells	–	4.1 (0.6, 7.6)	0.022
Current CD4 cell count/µL, per 100 cells	–	2.1 (0.4, 3.8)	0.018
Clinical AIDS before CART
No	156.1	2.4 (−10.9, 15.6)	0.72
Yes	153.7	0
Calendar year of CART initiation
1999–2001	153.2	−3.2 (−16.2, 9.8)	0.625
2002–2004	156.4	0
Patients who failed CART
No	155.3	0.1 (−15.0, 15.1)	0.995
Yes	155.2	0
Had at least one CART change
No	161.8	12.8 (0.4, 25.2)	0.043
Yes	149	0
Type of initial CART
NNRT-based	152.3	−7.7 (−20.3, 5)	0.235
PI-based	160	0
Type of CART during follow-up
Non-NNRT	162.6	12.4 (2.4, 22.4)	0.015
NNRT-based	150.1	0
Calendar year
<2003	144	−22.4 (−40.2, −4.6)	0.014
2003–2005	149.2	−17.2 (−31.2, −3.2)	0.016
2006–2007	153.1	−13.3 (−23.1, −3.5)	0.008
2008–2009	166.4	0
Positive for HCV antibody
Yes	163.7	−9.7 (−28.6, 9.2)	0.313
No	154.1	0

^aAdjusted for the linear and quadratic term of time and one independent variable.

^bLeast square means estimates from the model. MSM, men who have sex with men;

CART, combination antiretroviral therapy; NNRT, non nucleoside reverse transcriptase inhibitor;

PI, protease inhibitor.