Table 1.
Clinical, Laboratory, Utility, and Cost Model Input Parameters
| Parameters | Base case | Range | Distribution type* | Reference |
|---|---|---|---|---|
| Probabilities (%) | % | 95% confidence interval | ||
| Any CDI | 13.6 | 10.3–16.8 | Beta | 17 |
| Severe CDI | 23.8 | 19.0–28.5 | Beta | 18 |
| CDI-attributable death (initial CDI) | 7.3 | 5.7–8.9 | Beta | 19 |
| Death (first CDI recurrence) | 8.3 | 7.2–10.0 | Beta | 20 |
| Death (second CDI recurrence) | 4.2 | 2.3–5.5 | Beta | 20 |
| Death (subtotal colectomy) | 38.7 | 37.5–39.9 | Beta | 21, 22 |
| Subtotal colectomy | 0.16 | 0.06–0.25 | Beta | 23 |
| Cure (mild-moderate CDI, vancomycin) | 83.9 | 81.0–86.7 | Beta | 24, 25 |
| Cure (mild-moderate CDI, fidaxomicin) | 92.0 | 89.9–94.1 | Beta | 25 |
| Cure (severe CDI, vancomycin) | 88.6 | 86.1–91.1 | Beta | 24, 25 |
| Cure (severe CDI, fidaxomicin) | 82.1 | 79.1–85.1 | Beta | 25 |
| Cure (vancomycin taper and pulsed) | 69.0 | 61.9–76.1 | Beta | 26 |
| Cure (vancomycin + rifaximin) | 53.0 | 35.7–70.3 | Beta | 27 |
| Recurrence (mild-moderate CDI, vancomycin) | 24.4 | 21.0–27.8 | Beta | 24, 25 |
| Recurrence (mild-moderate CDI, fidaxomicin) | 16.8 | 13.9–19.7 | Beta | 25 |
| Recurrence (severe CDI, vancomycin) | 26.6 | 23.2–30.1 | Beta | 24, 25 |
| Recurrence (severe CDI, fidaxomicin) | 13.0 | 10.4–15.6 | Beta | 25 |
| Severe comorbidities and complications (post-colectomy) | 80.0 | 68.8–91.2 | Beta | 21, 22 |
| 1st recurrence (CDI) | 20.9 | 20.3–21.5 | Beta | 1 |
| Cure (IV metronidazole + vancomycin) | 84.1 | 73.3–94.9 | Beta | 28 |
| NAAT sensitivity | 95.0 | 92.0–97.0 | Beta | 29 |
| NAAT specificity | 98.0 | 97.0–99.0 | Beta | 29 |
| GDH sensitivity | 96.0 | 86.0–99.0 | Beta | 29 |
| GDH specificity | 96.0 | 91.0–98.0 | Beta | 29 |
| EIA sensitivity | 57.0 | 51.0–63.0 | Beta | 29 |
| EIA specificity | 99.0 | 98.0–99.9 | Beta | 29 |
| GDH/EIA sensitivity | 57.0 | 53.9–60.0 | Beta | 30 |
| GDH/EIA specificity | 99.4 | 99.3–99.6 | Beta | 30 |
| GDH/NAAT sensitivity | 91.5 | 89.6–93.1 | Beta | 30 |
| GDH/NAAT specificity | 98.0 | 97.7–98.3 | Beta | 30 |
| NAAT/EIA sensitivity | 54.2 | N/A | Invariant† | Calculated31, 32 (online Supplementary Table S1) |
| NAAT/EIA specificity | 99.9 | N/A | Invariant | Calculated31, 32 (online Supplementary Table S1) |
| Utilities | 95% confidence interval | |||
| Healthy (age 65) | 0.88 | 0.86–0.90 | Beta | 33 |
| Mild-moderate CDI | 0.78 | 0.43–1.13 | Beta | 34 |
| Severe CDI | 0.68 | 0.30–1.05 | Beta | 34 |
| Mild-moderate post-colectomy | 0.85 | 0.84–0.86 | Beta | 33 |
| Severe post-colectomy | 0.75 | 0.68–0.81 | Beta | 33 |
| Death | 0 | N/A | N/A | |
| Direct medical cost | 2017 US$ | Range | ||
| Hospitalization cost | $12,584.16 | ± 0.25 ($9438.12–15,730.20) | Gamma | 3 |
| Subtotal colectomy | $27,604.18 | ± 0.25 ($20,703.14–34,505.23) | Gamma | 35 |
| Fidaxomicin 200 mg | $2545.60 | N/A | Invariant | 36 |
| Vancomycin 125 mg | $863.20 | N/A | Invariant | 36 |
| Vancomycin tapered/pulsed | $1467.44 | N/A | Invariant | 36 |
| Rifaximin | $1636.80 | N/A | Invariant | 36 |
| Vancomycin + IV metronidazole | $132 | N/A | Invariant | 36 |
| NAAT | $40.77 | N/A | Invariant | 6, 8 |
| GDH | $13.87 | N/A | Invariant | 6, 8 |
| EIA | $11.30 | N/A | Invariant | 6, 8 |
| Long-term post-colectomy costs: 1 or 2 chronic conditions (annual) | $21,521.69 | ± 0.25 ($16,141.27–26,902.11) | Gamma | 37 |
| Long-term post-colectomy costs: 2+ chronic condition (annual) | $46,842.94 | ± 0.25 ($35,132.21–58,553.68) | Gamma | 37 |
| Costs associated with adverse events | $2.88 | ± 0.25 ($2.16–3.60) | Gamma | 36, 38 |
| Indirect costs | 2017 US$ | |||
| Inpatient treatment (IV metronidazole + vancomycin, fidaxomicin, or vancomycin) | $2257.92 | N/A | Invariant | 39 |
| Inpatient treatment (vancomycin tapered/pulsed) | $7056.00 | N/A | Invariant | 39 |
| Hospitalization (subtotal colectomy) | $5644.80 | N/A | Invariant | 39 |
| Travel, wait, and screen test | $141.12 | N/A | Invariant | 39 |
NAAT nucleic acid amplification test, GDH glutamate dehydrogenase, EIA enzyme immunoassay, CDI Clostridioides difficile infection
*A beta distribution was assumed for binomial data. The beta distribution characterizes the distribution of continuous probabilities, is constrained on the interval 0–1, and is parameterized by two positive parameters, alpha and beta. A gamma distribution was assumed for cost data. The gamma distribution is constrained on the interval 0 to positive infinity, is conjugate to the Poisson, and is characterized by two parameters, denoted as alpha and beta
†Parameters were not varied in the probabilistic sensitivity analyses