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Table 2 Annual proportion tested for syphilis among HIV-positive participants in the OHTN Cohort Study, 2000-2009

From: Patterns of syphilis testing in a large cohort of HIV patients in Ontario, Canada, 2000–2009

  n observation % tested Unadjusted ratio of proportions (95%CI) Adjusted ratio of proportions (95%CI)
Calendar year     
  2000 1605 2.7   
  2001 1524 6.0   
  2002 1566 7.7   
  2003 1507 10.2   
  2004 1627 16.8   
  2005 1616 32.6   
  2006 1580 43.3   
  2007 1592 43.6   
  2008 2767 42.3   
  2009 3324 54.6   
  Each additional calendar year (a)     
  2003 cf 2002    1.59 (1.54, 1.69) 1.53 (1.48, 1.58)
  2005 cf 2004    1.39 (1.36, 1.42) 1.32 (1.30, 1.35)
  2009 cf 2008    1.05 (1.03, 1.08) 0.98 (0.96, 1.01)
STI risk status     
  MSM 12,912 31.7 1.39 (1.27, 1.53) 1.20 (1.11, 1.30)
  Non-MSM males 2,877 22.6 Referent Referent
  Females 2,642 26.2 1.17 (1.03, 1.32) 1.03 (0.93, 1.14)
  Unknown 277 47.3   
Region     
  Toronto 10,014 31.7 1.19 (1.11, 1.27) 0.83 (0.78, 0.88)
  Ottawa 2,527 26.9 0.89 (0.80, 0.99) 0.70 (0.64, 0.77)
  Other 6,167 27.8 Referent Referent
Age (b)     
  <30 years 576 41.8 Referent Referent
  30+ years 18,132 29.4 0.72 (0.64, 0.81) 0.89 (0.81, 0.97)
Race/ethnicity     
  White 13,322 28.6 Referent  
  Black/African 1,463 28.9 1.01 (0.90, 1.13)  
  Aboriginal 1,092 32.6 1.13 (1.00, 1.27)  
  Other 2,363 33.4 1.17 (1.08, 1.27)  
  Unknown 468 42.5   
Nature of care provided at OCS clinic     
  Primary 4,242 44.5 1.74 (1.64, 1.84) 1.34 (1.27, 1.41)
  Tertiary 14,466 25.5 Referent Referent
Diagnosed with HIV in current or preceeding year (b)     
  No 18,330 29.1 Referent Referent
  Yes 378 63.5 1.88 (1.73, 2.04) 1.29 (1.19, 1.41)
Syphilis testing in previous year (b)     
  Not tested 13,995 18.3 Referent Referent
  Non-reactive 3,755 62.0 4.90 (4.69, 5.12) 1.75 (1.66, 1.84)
  Reactive 888 73.6 5.45 (5.18, 5.73) 2.01 (1.89, 2.15)
Test result undetermined (c) 70 35.7   
Initiated HIV antiretoviral treatment (b)     
  Yes 17,620 29.2 0.75 (0.68, 0.83) 0.92 (0.86, 0.99)
  No 1,088 38.6 Referent Referent
Number of routine HIV tests in year (b, d)     
  None 451 4.2 0.18 (0.11, 0.29) 0.23 (0.14, 0.40)
  One 1186 23.4 Referent Referent
  Two or more 17071 30.9 1.32 (1.20, 1.45) 1.27 (1.16, 1.40)
  1. Each observation represents a single calendar year of active follow-up. We calculated ratios of proportions using Poisson regression within a generalized estimating equation framework to account for repeated observations. The within-subject correlation coefficient was 0.40 in an intercept-only model. The adjusted model included all covariates shown except ethnicity.
  2. (a) There were statistically significant quadratic effects of calendar year. Beta coefficients for the linear and quadratic terms were 1.89 (95%CI 1.79, 2.01) and 0.966 (95%CI 0.962, 0.971) in the unadjusted model, and 1.84 (95%CI 1.74, 1.94) and 0.964 (0.960, 0.969) in the adjusted model, respectively.
  3. (b) Time updated each calendar year.
  4. (c) Reasons for unavailable test results in the preceding year included that the specimens were not tested or results were pending.
  5. (d) The number of routine HIV tests in the year was defined as the maximum of the total number of HIV viral load or the total number of CD4 cell count tests in a calendar year, whichever was greater. It is a proxy measure of the frequency of contact with HIV care.