TABLE 1. Baseline values and ranges for model variables.a.
| Variable [reference] | Baseline value | Sensitivity analyses |
|---|---|---|
| Population coverage of screening program | 80% | 40%, 60% |
| Results visit compliance3,4b | ||
| CM and Pap | Phase 1: 100% Phase 2: 100% |
Phase 2: 90% |
| ST | Phase 1: 100% Phase 2: 100% |
Phase 2: 90% |
| Cryotherapy compliance3,4b | ||
| CM and Pap | NA | NA |
| ST | Phase 1: 100% Phase 2: 97.3% |
Phase 2: 95.0% |
| Colposcopy compliance3,4b,c | ||
| CM and Pap | Phase 1: 88.2% Phase 2: 79.1% |
Phase 2: 75.0% |
| ST | Phase 1: 100% Phase 2: 53.6% |
Phase 2: 39.7% |
| Treatment compliance3,4b,c | ||
| CM and Pap | Phase 1: 85.5% Phase 2: 54.4% |
Phase 2: 49.0% |
| ST | Phase 1: 87.5% Phase 2: 52.4% |
Phase 2: 29.7% |
| Test sensitivity/specificity for CIN2+ | ||
| HPV, provider collection19 | 0.78/0.89 | 0.67/0.86 |
| Pap, 30-49 y19 | 0.41/0.94 | 0.70/0.90 |
| Pap, >50 y20 | 0.33/0.94 | 0.70/0.90 |
| Test sensitivity/specificity for CIN1+, colposcopy3d | 0.98/0.03 | 1.0/1.0 |
| Eligibility for cryotherapy, ST cohort4,21 | ||
| No lesion or CIN1 | 90% | 75% |
| CIN2 | 85% | 60% |
| CIN3 | 75% | 49% |
| Cancer | 10% | 10% |
| Effectiveness of cryotherapy, ST cohort20,22,23e | 88% | 75% |
| Proportion of women retaining an HPV infection following cryotherapy, ST cohort | 15% | 30% |
| Effectiveness of treatment with cryotherapy or LEEP following colposcopy23e | 94% | 85% |
| Proportion of women retaining an HPV infection following colposcopic diagnosis and treatment | 10% | 30% |
| Direct medical costs (US$)5 | ||
| HPV test (clinic)f | $7.10 | $9.60-$17.10 |
| Pap (clinic) | $4.54 | 50%-150% |
| Colposcopy and biopsy (hospital) | $88.01 | 50%-150% |
| Cryotherapy (clinic or hospital)e,g | $9.70 | 50%-150% |
| LEEP (hospital)e | $45.79 | 50%-150% |
| Simple hysterectomye | $813.97 | |
| Pap (hospital; follow-up after treatment at hospital) | $3.99 | 50%-150% |
| Direct non-medical costs (US$)5,17h | 50%-150% | |
| Transportation (round-trip, clinic) | $0.76 | |
| Transportation (round-trip, hospital) | $3.05 | |
| Transportation (round-trip, cancer center) | $8.14 | |
| Women's time costs (US$) | ||
| Screening | $5.23 | |
| Cryotherapy (clinic, ST cohort) | $4.12 | |
| Colposcopy | $8.98 | |
| Cryotherapy (hospital) | $8.60 | |
| LEEP | $8.98 | |
| Simple hysterectomy | $53.97 | |
| Treatment of local cancer (US$) (FIGO stages 1a-2a) | $4570 | 50%-150% |
| Treatment of regional/distant cancer (US$) (FIGO stages ≥2b) | $5481 | 50%-150% |
Abbreviations: CIN, cervical intraepithelial neoplasia; CIN1+, cervical intraepithelial neoplasia grade 1 or higher; CIN2+, cervical intraepithelial neoplasia grade 2 or higher; CM, colposcopy management cohort; FIGO, Federation Internationale de Gynecologies et Obstetriques; LEEP, loop electrosurgical excision procedure; ST, screen and treat cohort; US$, 2014 United States dollars.
Phase 1 and phase 2 results were compared in the baseline analysis, with all variables equivalent except for compliance variables and age-specific prevalence of high-risk HPV. Cost data were originally collected in 2012 US$ (with the exception of the HPV test), and were converted to 2014 US$ using El Salvador gross domestic product deflators. The sensiti vity analysis ranges for cost data were applied to the original 2012 US$.
Compliance for Pap was assumed to be the same as CM. In sensitivity analyses, we examined the impact of compliance with each visit at the lower bound of the 95% confidence intervals indicated by the study. Because all women in the study received their HPV results, it was assumed in sensitivity analysis that only 90% received results.
In the ST cohort, compliance with colposcopy and treatment was only relevant for women who were determined to be ineligible for cryotherapy at the clinic.
Test performance characteristics of colposcopy were based on the worst diagnosis of the local pathologist relative to the gold standard (i.e., worst diagnosis by a quality control pathologist), at a treatment threshold of CIN1+.
For ST, cryotherapy was assumed to occur at the clinic for eligible women. For women requiring treatment after colposcopy (i.e., women in CM diagnosed with CIN1+; women in ST deemed ineligible for cryotherapy at the clinic), treatment with cryotherapy, LEEP, or simple hysterectomy was assumed to occur at the hospital as follows (based on study data): <CIN2, 99.6% cryotherapy, 0.3% LEEP, 0.1% simple hysterectomy; CIN2: 92.7% cryotherapy, 4.5% LEEP, 2.7% simple hysterectomy; CIN3: 53.4% cryotherapy, 28.6% LEEP, 18% hysterectomy.4 The effectiveness of cryotherapy includes management of residual disease detected during follow-up. It was assumed that women receiving cryotherapy or LEEP would receive follow-up including a Pap test at the clinic (for ST) or hospital (for CM or ST deemed ineligible for immediate cryotherapy) and a colposcopy in the year following treatment, with 1% of women receiving an additional Pap following a positive colposcopy result.
This includes the cost of the HPV test, which was assumed to be 2014 US$5.
On average, it was assumed 30 women could be treated per US$286 nitrous oxide tank refill.
Details regarding the valuation of women's time and transportation have been previously described.5