Table 1. Clinical and Economic Variables.
| Variable | Estimate | Range* | Reference | |||
|---|---|---|---|---|---|---|
| Clinical Inputs | ||||||
| Probability of Disease Flare On Maintenance Therapy (q3 months) | ||||||
| No medical therapy | 0.22 | 0.19-0.25 (B) | 4 | |||
| 5-ASA | 0.12 | Calculated | 4 | |||
| Azathiopurine | 0.13 | 0.10-0.18 (B) | 21 | |||
| Infliximab | 0.21 | 0.17-0.26 (B) | 22 | |||
| Odds Ratios | ||||||
| Flare on 5-ASA maintenance therapy | 0.47 | 0.36-0.62 (N) | 4 | |||
| Probability of Response To Treatment During Active Disease | ||||||
| Intensive 5-ASA | 0.64 | 0.50-0.76 (B) | 23 | |||
| Corticosteroids (oral) | 0.84 | 0.50-0.92 (B) | 24 | |||
| Corticosteroids (intravenous) | 0.67 | 0.48-0.85 (B) | 25 | |||
| Infliximab | 0.70 | 0.50-0.90 (B) | 26, 27 | |||
| Utilities | ||||||
| Quiescent disease | 0.98 | 0.91-1.00 (B) | 36 | |||
| Active disease without hospitalization | 0.90 | 0.79-0.99 (B) | 36 | |||
| Active disease with hospitalization | 0.59 | 0.47-0.71 (B) | 1, 37 | |||
| Post-colectomy | 0.92 | 0.84-0.99 (B) | 36 | |||
| Maintenance medication (disutility) | 0.005 | 0-0.01 (U) | 17 | |||
| Stool testing (disutility) | 0.0025 | 0-0.01 (U) | 38 | |||
| Stool Test Diagnostic Test Characteristics | ||||||
| Sensitivity for impending flare | 0.77 | 0.5-1.0 (B) | 15 | |||
| Specificity for impending flare | 0.71 | 0.5-1.0 (B) | 15 | |||
| Death | ||||||
| Colectomy (peri-operative period) | 0.023 | 0.01-0.10 (B) | 30 | |||
| Non-colectomy death | Age dependent | Not varied | 20 | |||
| Economic Inputs | ||||||
| Outpatient Costs (2009 US Dollars) (per year) | ||||||
| Mesalamine (2.4 g po qD) | $3,408 | $1,704 - $6,816 (G) | 31 | |||
| Mesalamine (4 g pr qD) | $9,415 | $4,707 - $18,830 (G) | 31 | |||
| Azathioprine (200 mg po qD) | $961 | $480 - $1,922 (G) | 31 | |||
| Infliximab (5 mg/kg q8 weeks) | $19,800 | $9,900 - $39,600 (G) | 32 | |||
| Post-colectomy care (initial 6 months) | $26,660 | $13,330 - $53,320 (G) | 19 | |||
| Post-colectomy care (subsequent years) | $3,329 | $1,664 - $6,658 (G) | 19 | |||
| Stool test (q3 months) (annual cost) | $740 | $370 - $1,480 (G) | See text | |||
| Inpatient Costs (2009 US Dollars) | ||||||
| Hospitalization for disease flare (DRG 387) | $5,861 | $2,930 - $11,722 (G) | 33 | |||
| Infliximab 5 mg/kg induction (3 doses) | $9,900 | $4,950 - $19,800 (G) | 32 | |||
| Colectomy (ICD-9 code 45.8) | $25,623 | $12,811 - $51,246 (G) | 33 | |||
| Other | ||||||
| Prednisone (3 month taper) | $6 | $3 - $12 (G) | 31 | |||
| Outpatient physician visit (HCPCS 99214) | $69 | $34 - $138 (G) | 34 | |||
| Discount rate | 0.03 | 0.00-0.05 (B) | 39 | |||
*
B, G, N, and U signify type of distribution used for probabilistic sensitivity analysis (beta, gamma, normal, or uniform).