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Table 1 Parameter values used in calculations

From: A systematic review of heterosexual anal intercourse and its role in the transmission of HIV and other sexually transmitted infections in Papua New Guinea

Model parameter Representative value
Per-act male-to-female HIV transmission probability during vaginal intercoursea 0.0008
Per-act male-to-female HIV transmission probability during anal intercoursea 0.0143
Anal sex behavior based on review results
Probability of condom use during vaginal intercourse–Women in general populationb 20%
Probability of condom use during anal intercourse–Women in general populationb 10%
Probability of condom use during vaginal intercourse–Women at high riskb 40%
Probability of condom use during anal intercourse–Women at high riskb 20%
Proportion of women in general population who engage in HAI each yearc 20%
Proportion of women at high risk who engage in HAI each yearc 50%
Proportion of sex acts that involve anal intercourse–Women in general population who engage in HAId 10%
Proportion of sex acts that involve anal intercourse–Women at high risk who engage in HAId 20%
Behavioral and epidemiological characteristics for PNG
Number of sex acts per year–unmarried women in general populatione 10
Number of sex acts per year–Women in general population with a regular partner 100
Number of sex acts per year–Women at high riske 250
HIV prevalence in male partnersf 1%
  1. a: Male to female vaginal transmission based on [11]. For HIV transmission through HAI this is assumed to be the same as for male-to-male transmission. These values are from a systematic review for homosexual men in Australia and represent the probability of HIV transmission for receptive anal intercourse with ejaculation [53].
  2. b: Condom use for HAI assumed based on data from our systematic review on condom use during last act (Table 1). From our review condom use for HAI at last HAI act varied between 4% and 19%, depending on population, but the number of people surveyed were small. Vaginal intercourse condom use assumed to have higher values based on our findings that it is universally higher than for HAI [5, 30]. Women at high risk assumed to have a higher condom use than women in general population with values based on behavioral data from PNG reviewed in [54]. Based on this information we assumed condom use during last act of HAI to be 10% for the general population and 20% for women at high risk.
  3. c: Assumed values obtained in our systematic review (Table 3). According to our review 18% to 24% of female youth out of school engaged in HAI in the last 12 months. For calculation purposes, we assume this is a reasonable representation of the behavior of women in the general population and assume 20% of females in the general population engage in HAI each year. Data for HAI in the last month, 3 months, and 6 months in Table 3 suggest HIA is substantially more common amongst FSW, generally over 50% for each period. We therefore assumed 50% of women at high-risk engage in HAI each year.
  4. d: Assumption as there is no available frequency data for HAI. We assume HAI is more frequent for women at high risk.
  5. e: Values based on behavioral data from PNG on the number of casual partners reviewed in [54].
  6. f: Based on estimates from the National Department of Health [55].
  7. Each parameter is given a representative value based on the data obtained from the systematic review or assumed where no data was found.