Table 1

Description, point values, range and sources for all variables used in a cost-effectiveness model of different algorithms of HIV and syphilis testing in pregnancy

VariableBase-case valueRangeSources
Maternal characteristics
 Median age at first birth20w18
Disease prevalence
 HIV prevalence among pregnant women10.6%5.3%–15.9%*28
 AIDS prevalence among HIV-infected pregnant women24.82%Assumption
 Syphilis prevalence among HIV-uninfected pregnant women1.09%0.54%–1.63%*28
 Syphilis prevalence among HIV-infected pregnant women2.17%1.09%–3.26%*28
 History of syphilis infection (adequately treated previous infections) in HIV-uninfected women5%2.5%–7.5%*Assumption
 History of syphilis infection (adequately treated previous infections) in HIV-infected women10%5%–15%*Assumption
Disease progression
 Average progression time for HIV to AIDS in treated child10 yearsAssumption
 Average progression time for AIDS to death in treated child5 yearsAssumption
 Average progression time for HIV to AIDS in untreated child1 yearAssumption
 Average progression time for AIDS to death in treated child1 yearAssumption
Test performance
 Syphilis test sensitivity
  Dual HIV and syphilis test0.890.84–0.9420
  Syphilis rapid0.820.63–0.9730 w1 w2
  Syphilis laboratory-based124
 Syphilis test specificity
  Dual HIV and syphilis test0.990.97–1.0020
  Syphilis rapid0.960.92–0.9930 w1 w2
  Syphilis laboratory-based1w16
 Syphilis test specificity in those with previously treated syphilis infection
  Dual HIV and syphilis test0.91Assumption
  Syphilis rapid0.91w1
  Syphilis laboratory-based1
 HIV test sensitivity
  Dual HIV and syphilis test0.990.95–1.0020
  HIV rapid1w10
 HIV test specificity
  Dual HIV and syphilis test0.990.997–0.99920
  HIV rapid0.960.85–1w10
Loss-to-follow-up
 Syphilis loss-to-follow-up (for laboratory tests)20%w19
 HIV loss-to-follow-up23.9%w20
HIV and syphilis treatment
 Infants born to women who test positive for HIV and receive treatment who receive nevirapine77.19%Assumption
 Proportion of children known to be HIV-exposed who were enrolled in ART67%28
 Probability of syphilis treatment success for the mother98%w16
Pregnancy outcomes
 Syphilis-uninfected mothers
  Stillbirth/early fetal death4.6%3.0%–7.1%3
  Neonatal death3%2.1%–4.3%3
  Prematurity or low birth weight6.3%3.5%–11.0%3
  MTCT of HIV in HIV-treated mothers (in utero+intrapartum/postnatal, 12 month)4.99%w21
  MTCT of HIV in HIV-untreated mothers (in utero+intrapartum/postnatal, 12 month)24.17%w22
 Syphilis-infected mothers (syphilis-untreated)
  Congenital syphilis15.5%7.5%–29.0%3
  Prematurity or low birth weight12.1%3.9%–31.8%3
  Neonatal death12.3%9.3%–16.2%3
  Stillbirth/early fetal death25.6%18.5%–34.2%3
Additional effects in HIV-coinfected mothers (HIV-treated)
  MTCT of HIV in HIV-treated mothers (in utero+intrapartum/postnatal)9.05%29
  Prematurity or low birth weight2.74%3
Additional effects in HIV-coinfected mothers (HIV-untreated)
  MTCT of HIV34.5%29
  Prematurity or low birth weight and MTCT of HIV9.36%3 29
Costs (2012 US dollars)
 Labour costs
  Pretest counselling (both HIV and syphilis)$0.44w5†
  Sample collection (single test)$0.27w5†
  Preparing and inoculating test (single test)$0.3724
  Reading and recording results (single test)$0.6324
  Post-test counselling, syphilis positive$0.62w5†
  Post-test counselling, syphilis negative$0.18w5†
  Post-test counselling, HIV positive$1.24w5†
  Post-test counselling, HIV negative$0.18w5†
 Patient cost
  Travel cost$1.49Assumption
  Testing time cost (dual test)$0.4824
  Testing time cost (single tests)$0.71Assumption
 Test cost
  Single syphilis rapid test$0.55WHO catalogue
  Single HIV rapid test$0.81UNICEF agreement
  Laboratory-based syphilis tests$2.53w13
  Dual HIV and syphilis test$1.30$1.20–$2.60Assumption
  Early infant diagnosis$32.50w23
 Treatment for syphilis (2.4 MU benzathine penicillin)$2.38w16
 Pregnancy outcome cost
  Healthy$72.5936.30–108.89*w16
  Congenital syphilis$804.54402.27–1206.81*w16
  Premature$1508.84754.42–2263.26*w16
  Neonatal death$3577.581788.79–5366.37*w16
  Stillbirth$72.5936.30–108.89*w16
  MTCT HIV$1358.18679.09–2037.27*w24
  Nevirapine for 12 months for infant$16.608.30–24.90*
Disability weights
 AIDS (no treatment)0.54525
 HIV0.05325
 Death1
 Congenital syphilis (3 years)0.31526
 Low birth weight (1 year)0.10626
 Neonatal death1
 Stillbirth0
 Miscarriage0
Test uptake
 Syphilis rapid test0.080.04–0.12*w9
 Syphilis laboratory test0.080.04–0.12*w9
 HIV rapid test0.830.415–0.95‡w9
 Dual HIV and syphilis test0.830.415–0.95‡Assumption
 Early infant diagnosis0.9w23
Other
 Life expectancy of newborn50 yearsw25
 Discount rate3%w26
  • Women are assumed to have unknown HIV and syphilis status at time of testing.

  • *Ranges calculated using a 50% spread.

  • †Labour costs were calculated using salaries published by the WHO (w5) and assumed times for length of each procedure.

  • ‡Ranges are calculated using a 50% reduction for the lower bound and an assumption for the top.

  • ART, antiretroviral therapy; MTCT, maternal-to-child transmission.