Inferences regarding the effect of VL on HPV detection and clearance, and the effect of HPV on VL, can be made by comparing these hazard rates. Hypotheses are tested by fitting unrestricted and restricted models and using likelihood ratio tests. RAD001 research buy Mathematical details are given in the Appendix. A similar model was used to assess HPV detection and clearance rates with varying CD4 cell count (the CD4 model; Fig. 1b). The cause-specific hazard rates are represented by γs. The four states were defined as follows: 1 = HPV negative and CD4 count ≤350 cells/μL; 2 = HPV positive and CD4 count ≤350 cells/μL; 3 = HPV negative and CD4 count >350 cells/μL, and
4 = HPV positive and CD4 count >350 cells/μL. learn more The threshold of 350 cells/μL was chosen to be consistent with guidelines on when to start antiretroviral therapy at the time of A5029. The parameter estimates (and standard errors) using set 2 are shown in Figure 1, and model fits are presented in the Appendix. The times to final visit were compared between groups with different baseline characteristics (HPV, VL and CD4 cell count statuses) using log-rank tests. Analyses were conducted using sas 9.1 (SAS Institute, Cary, NC) and R 1.8.1 (R Foundation for Statistical Computing, www.R-project.org). Of the 147 study subjects included in the analysis, both HPV and HIV RNA results
were available for 143 at baseline, 119 at week 24, 103 at week PD184352 (CI-1040) 48 and 85 at week 96. Data for times outside the scheduled visits for some subjects were also included in the analysis. Seventy subjects had four visits, 41 had three, 18 had two, and 18 had only one. Of the 143
subjects with both HPV and HIV RNA results at baseline, 120 subjects (84%) had VL > 400 copies/mL and 80 subjects (56%) had HPV infection. There was a trend for earlier discontinuation in subjects starting with HPV infection compared with those without HPV infection, but the time to final visit was not significantly different (P = 0.13). The final visit times for subjects starting with VL>400 and ≤400 copies/mL were not significantly different. In the VL model (Fig. 1a), the comparison between λ12 and λ34 marginally suggested that a woman with current VL > 400 copies/mL was more likely to acquire HPV than a woman with VL ≤ 400 copies/mL, using set 1 (hazard ratio λ12/λ34 = 4.67; P = 0.068). However, no such association was suggested using set 2 (λ12/λ34 = 2.64; P = 0.34). Results of other comparisons were similar for the two HPV sets. There was no indication of a significant difference between subjects with VL > 400 and VL ≤ 400 copies/mL in clearance of HPV (λ21/λ43 = 0.632; P = 0.55) or between HPV-positive and HPV-negative subjects in VL increase (λ31/λ42 = 0.656; P = 0.69) and VL decrease (λ13/λ24 = 0.983; P = 0.98) using both HPV sets (set 2 results are shown).