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Table 3 Serosorting: extrapolated country MSM population

From: Men having sex with men serosorting with casual partners: who, how much, and what risk factors in Switzerland, 2007-2009

  Gaysurvey sample data Extrapolated to country MSM population (17–74 yr.)
a) Restricted definition (sex only with men, mainly with men, and with as many women as men, lifetime) b) Enlarged definition (at least one partner of same sex, lifetime)
N  % CI 95% c % Among Serosorters % Mean number of sexual partners with AId N Mina/maxa N Minb/maxb
Pooled Gaysurvey data (2007-2009) 4882 100       33,700    70,300
 UAI with casual partnersa 647 13.3 12.3 - 14.2   11 ± 1 4466 4150/4798 9317 8656/10,008
 Serosorting with casual partnersb 247 5.1 4.5 - 5.7 N = 247 11 ± 1 1705 1503/1925 3557 3136/4015
  Serostatus declared
  HIV-positive 44 0.9 0.7 - 1.2 17.8 18 ± 2 304 221/407 634 461/849
  Detectable viral load and No STIe 10 0.2 0.1 - 0.4 4.0 17 ± 5 69 33/127 144 69/265
  Undetectable viral load and No STI 15 0.3 0.2 - 0.5 6.1 18 ± 4 104 67/169 216 141/352
  Undetectable viral load and STI 12 0.2 0.1 - 0.4 4.9 15 ± 4 83 43/145 173 89/302
  Detectable viral load and STI 7 0.1 0.1 - 0.3 2.8 24 ± 5 48 19/99 101 41/208
  HIV-negative 164 3.4 2.9 - 3.9 66.4 10 ± 1 1132 968/1316 2362 2019/2744
  Tested in the past 12 months 112 2.3 1.9 - 2.8 45.3 11 ± 1 773 638/928 1613 1331/1936
  Not tested in the past 12 months 52 1.1 0.8 - 1.4 21.1 8 ± 1 359 268/470 749 560/980
 N.A, D.K, Not testedf 39 0.8 0.6 - 1.1 15.8 10 ± 2 269 192/367 562 400/767
  1. a: Unprotected anal intercourse (UAI) in the past 12 month.
  2. b: Among respondents who had UAI with casual partners in the past 12 months (N = 647).
  3. c: Confidence interval (CI) calculated with the exact binomial distribution.
  4. d: Anal intercourse in the past 12 months.
  5. e: Sexually transmitted infections (STIs) in the past 12 months.
  6. f: N.A: No answer; D.K: Don’t know.