Table 1

Model parameters
Parameter Details Value Distribution Source
Type
Population characteristics
Population size 2,000
Time spent in model (years) (min, max, mode) 1, 34, 17 Triangular [27]; assumption
Proportion of MSM who are HIV positive 0.2 [29]; assumption
Syphilis natural history
Probability of transmission (per act) (min, max, mode) Penile-anal/Penile-oral 0.01, 0.05, 0.014 Triangular [26]; assumption
Incubation period (days) 21-28 Uniform discrete [30]
Infection/infectious period (days) [16,31,32]
Primary 45-60 Uniform discrete
Secondary 100-140 Uniform discrete
Early latent* 365
Recurrent 90
Late Latent* Until end of life in model
Probability of recurrent syphilis 0.25 [33]
Duration of protective immunity following [21,34,35]
treatment (years)
Primary or secondary syphilis 0
Latent syphilis 5
Partnership characteristics
Number of partners in past 6 months (proportion of population in each category) [27]
1 0.28
2-9 0.48
10-29 0.15
30-75 0.09
Maximum number of partnersin past 6 months (by partner number category) (min, max, mode)
1 1 Assumption
2-9 2,9,8 Triangular
10-29 10,29,25 Triangular
30-75 30,75,50 Triangular
Duration of partnership (days) (min, max, mode) [27]; Assumption
Casual 1,2,1 Triangular
Regular 7,3000,365 Triangular
Behavioural characteristics
Frequency of anal sex (per day) [26]
Casual partnership 0.7
Regular partnership 0.3
Frequency of oral sex (per day) [26]
Casual partnership 1
Regular partnership 0.3
Probability of condom use (anal sex) [2,27]
HIV-concordant 0.5
HIV-discordant 0.8
Condom efficacy Assume condom use for anal intercourse only 0.9 [36]
Test and Treatment characteristics
Probability of seeking medical care for symptoms [19,37]
Primary 0.25
Secondary 0.60
Time to treat (days) Primary 3-56 Uniform [38]; assumption
Secondary 1-57 Uniform
Proportionof population screened routinely for [19,24,39,40];
syphilis assumption
HIV positive 0.5
HIV negative 0.2
Test sensitivity Treponemal-specific screening test 0.95 [41,42]
Probability of partner notification Assumption
Casual partner 0.1
Regular partner 0.6
Trace-back period for partner notification [43]
(months)
Primary 3
Secondary 6
Early latent 12
Time from index case identification to screening of named partner(s) (days) 3-21 Assumption

*Not infectious.

Tuite et al.

Tuite et al. BMC Public Health 2013 13:606   doi:10.1186/1471-2458-13-606

Open Data