Table 2.
Results of base-case analysis and scenario analyses
| Scenario | FC testing strategy | Standard practice (blood test) |
Incremental Cost | Incremental QALY | ICER ($C/QALY) |
Probability of FC being cost-effective(%)* | ||
| Cost to $C | QALY | Cost to $C | QALY | |||||
| Base case | 295.12(274.49 to 317.53) | 0.751 (0.431 to 0.939) | 273.93 (245.40 to 306.05) | 0.750 (0.430 to 0.938) | 21.19 (−7.50 to 46.57) | 0.001 (0.0003 to 0.002) | 20 323.35 | 81.3 |
| Scenario analyses IBD prevalence to % | ||||||||
| 5 | 286.17 (268.43 to 306.09) | 0.757 (0.427 to 0.943) | 264.65 (238.41 to 294.96) | 0.756 (0.426 to 0.942) | 21.52 (−7.75 to 46.72) | 0.001 (0.0002 to 0.002) | 24 440.81 | 75.5 |
| 10 | 312.60 (295.98 to 331.11) | 0.743 (0.434 to 0.928) | 291.21 (267.12 to 319.28) | 0.742 (0.433 to 0.927) | 21.39 (−5.67 to 45.80) | 0.001 (0.0004 to 0.003) | 15 594.08 | 89.3 |
| 15 | 339.26 (323.00 to 357.86) | 0.740 (0.448 to 0.916) | 318.14 (294.04 to 345.63) | 0.738 (0.447 to 0.915) | 21.12 (−5.02 to 43.94) | 0.002 (0.0004 to 0.005) | 11 515.23 | 93.8 |
| 20 | 365.81 (350.40 to 383.68) | 0.728 (0.442 to 0.907) | 344.93 (322.74 to 371.08) | 0.725 (0.440 to 0.904) | 20.88 (−3.94 to 41.96) | 0.002 (0.0006 to 0.006) | 8843.74 | 96.7 |
| FC test accuracy (Turvill et al 12) | ||||||||
| Sensitivity=0.94 (95% CI 0.85 to 0.98) Specificity=0.92 (95% CI 0.90 to 0.94) |
285.36 (265.56 to 306.98) | 0.755 (0.431 to 0.939) | 274.16 (245.10 to 306.04) | 0.754 (0.430 to 0.937) | 11.21 (−16.20 to 35.83) | 0.001 (0.0005 to 0.003) | 8012.69 | 96.5 |
| Primary care practice accuracy (Waugh et al 7) | ||||||||
| Sensitivity=1 (7/7) Specificity=0.79 (82/104) |
295.55 (275.41 to 317.36) | 0.753 (0.446 to 0.938) | 312.85 (270.56 to 359.49) | 0.752 (0.445 to 0.937) | −17.30 (−62.90 to 22.76) | 0.001 (−0.0001 to 0.002) | N/A | 93.6 |
| Proportion of patients with abnormal blood test with endoscopy ordered in the initial gastroenterologist consultation to % | ||||||||
| 100 | 295.38 (274.60 to 317.32) | 0.751 (0.430 to 0.938) | 276.23 (248.77 to 307.54) | 0.750 (0.429 to 0.937) | 19.15 (−10.31 to 44.69) | 0.001 (0.0002 to 0.002) | 22 007.50 | 76.9 |
| Proportion of patients with no IBD with symptoms after further intensive management by GPs that need investigation by specialist and endoscopy to % | ||||||||
| 5 | 268.69 (251.37 to 286.92) | 0.754 (0.444 to 0.940) | 248.96 (222.27 to 278.72) | 0.753 (0.444 to 0.939) | 19.73 (−10.67 to 46.48) | 0.001 (0.0003 to 0.003) | 17 988.04 | 83.5 |
| 10 | 281.84 (263.26 to 301.20) | 0.754 (0.447 to 0.938) | 261.12 (234.23 to 290.74) | 0.753 (0.446 to 0.937) | 20.72 (−8.35 to 46.16) | 0.001 (0.0002 to 0.002) | 19 504.34 | 82.4 |
| 20 | 308.68 (286.39 to 332.03) | 0.751 (0.426 to 0.938) | 286.82 (257.72 to 318.88) | 0.750 (0.426 to 0.938) | 21.85 (−5.70 to 45.83) | 0.001 (0.0002 to 0.002) | 21 405.41 | 81.2 |
| 25 | 322.23 (297.17 to 350.17) | 0.749 (0.423 to 0.937) | 300.26 (268.29 to 334.99) | 0.748 (0.422 to 0.936) | 21.97 (−5.25 to 45.94) | 0.001 (0.0003 to 0.002) | 22 040.22 | 79.5 |
| 30 | 335.85 (308.40 to 366.80) | 0.750 (0.432 to 0.934) | 313.02 (280.31 to 348.54) | 0.749 (0.431 to 0.933) | 22.84 (−3.46 to 45.44) | 0.001 (0.0002 to 0.002) | 23 221.90 | 78.8 |
| Cost of FC to $C | ||||||||
| 20 | 275.24 (254.13 to 297.02) | 0.755 (0.446 to 0.940) | 273.98 (246.12 to 304.75) | 0.754 (0.445 to 0.939) | 1.26 (−27.32 to 25.62) | 0.001 (0.0002 to 0.002) | 1206.34 | 94.9 |
| 30 | 285.21 (264.91 to 307.09) | 0.753 (0.436 to 0.940) | 274.13 (246.69 to 306.58) | 0.752 (0.435 to 0.939) | 11.08 (−17.29 to 36.28) | 0.001 (0.0003 to 0.002) | 10 567.51 | 89.8 |
| 50 | 305.42 (284.54 to 327.76) | 0.751 (0.428 to 0.941) | 274.12 (246.34 to 305.69) | 0.750 (0.428 to 0.940) | 31.29 (2.93 to 55.78) | 0.001 (0.0003 to 0.002) | 29 789.72 | 71.7 |
| 60 | 315.60 (295.76 to 337.54) | 0.751 (0.430 to 0.936) | 274.19 (246.49 to 305.45) | 0.750 (0.430 to 0.936) | 41.40 (13.49 to 66.07) | 0.001 (0.0002 to 0.002) | 39 243.50 | 59.8 |
| 70 | 325.29 (305.29 to 347.98) | 0.753 (0.428 to 0.938) | 274.15 (246.63 to 305.86) | 0.751 (0.427 to 0.936) | 51.14 (22.70 to 75.99) | 0.001 (0.0002 to 0.002) | 48 712.48 | 47.4 |
| All cost estimates except FC test cost to $C | ||||||||
| +20% | 346.68 (321.97 to 372.92) | 0.752 (0.430 to 0.940) | 329.42 (295.89 to 367.82) | 0.751 (0.429 to 0.939) | 17.26 (−16.39 to 48.03) | 0.001 (0.0003 to 0.002) | 16 191.86 | 83.4 |
| −20% | 244.18 (227.92 to 262.28) | 0.752 (0.433 to 0.936) | 219.14 (196.94 to 244.50) | 0.751 (0.432 to 0.935) | 25.04 (2.13 to 44.91) | 0.001 (0.0003 to 0.003) | 23 509.13 | 79.8 |
| Utility decrement | ||||||||
| CD=0.006 (Gregor et al
32
UC=0.014 (Poole et al 33 |
295.11 (274.59 to 316.66) | 0.755 (0.427 to 0.941) | 274.24 (246.79 to 304.96) | 0.755 (0.427 to 0.940) | 20.87 (−6.50 to 45.47) | 0.001 (0.0002 to 0.001) | 30 136.89 | 68.6 |
| Time taken to follow-up by GP first time | ||||||||
| 1 month | 294.97 (274.80 to 316.36) | 0.756 (0.422 to 0.945) | 274.09 (245.92 to 306.40) | 0.755 (0.421 to 0.944) | 20.89 (−8.13 to 46.10) | 0.001 (0.0002 to 0.002) | 18 830.57 | 81.9 |
| 2 months | 295.36 (274.91 to 317.69) | 0.758 (0.437 to 0.943) | 274.07 (246.25 to 306.46) | 0.757 (0.436 to 0.942) | 21.29 (−7.90 to 45.83) | 0.001 (0.0002 to 0.002) | 19 650.08 | 81.7 |
| 4 months | 295.28 (275.08 to 317.76) | 0.749 (0.442 to 0.940) | 274.03 (245.76 to 304.35) | 0.748 (0.441 to 0.939) | 21.25 (−6.75 to 45.57) | 0.001 (0.0002 to 0.002) | 21 451.73 | 80.8 |
| Time taken to follow-up by a specialist | ||||||||
| 1 month | 295.47 (275.10 to 317.87) | 0.747 (0.425 to 0.937) | 274.37 (246.13 to 305.91) | 0.746 (0.424 to 0.936) | 21.10 (−7.54 to 46.45) | 0.001 (0.0002 to 0.002) | 23 213.73 | 76.1 |
| 2 months | 295.35 (275.19 to 318.36) | 0.757 (0.435 to 0.939) | 274.19 (247.23 to 305.55) | 0.756 (0.434 to 0.937) | 21.16 (−7.75 to 45.96) | 0.001 (0.0002 to 0.002) | 21 587.69 | 79.6 |
| 4 months | 295.49 (274.69 to 317.09) | 0.751 (0.430 to 0.940) | 274.42 (246.23 to 305.94) | 0.750 (0.429 to 0.939) | 21.07 (−7.51 to 46.49) | 0.001 (0.0003 to 0.003) | 18 991.77 | 83.4 |
| Patient population without gastrointestinal alarm symptoms (Walker et al 11) | ||||||||
| Prevalence=4% (18/447) Sensitivity=0.84 (15/18) Specificity=0.91 (390/429) |
276.29 (253.94 to 299.86) | 0.760 (0.429 to 0.948) | 258.90 (230.11 to 291.19) | 0.760 (0.429 to 0.947) | 17.40 (−13.70 to 44.78) | 0.001 (0.0002 to 0.002) | 21 608.85 | 75.6 |
95% CI values in brackets.
*At $C50 000/QALY threshold.
CD, Crohn’s disease; FC, faecal calprotectin; GP, general practitioner; IBD, inflammatory bowel disease; ICER, incremental cost-effectiveness ratio; QALY, quality-adjusted life year; UC, ulcerative colitis.