Parameter | Value | α | β |
Starting cohort characteristics (percentage)*12 | |||
Male | 52.7 | 5999 | 5394 |
Asymptomatic without COPD | 43.0 | 364 | 482 |
Symptomatic without COPD | 48.2 | 364 | 482 |
Undiagnosed COPD | 8.8 | 74 | 772 |
Proportion in GOLD stage 1 | 69.0 | 58 | 26 |
Proportion in GOLD stage 2 | 27.4 | 23 | 61 |
Proportion in GOLD stage 3 | 3.6 | 3 | 81 |
Natural history of development of COPD (percentage per year) | |||
Development of symptoms†46 47 | 2.0 | 135 | 6775 |
Incidence of COPD*‡ 48 | .6 | 55 | 9945 |
Proportion of incident cases in GOLD stage 1§49 | 72.2 | 44 | 17 |
Proportion of incident cases in GOLD stage 2§49 | 27.8 | 17 | 44 |
Routine practice (percentage)12 | |||
Probability of being diagnosed with COPD | 0.8 | 337 | 41 692 |
Treatment after COPD diagnosis | 29.3 | 3972 | 9585 |
Systematic case-finding activities (percentage)12 | |||
Received questionnaire | 99.9 | 12 175 | 1 |
Responded to questionnaire | 35.5 | 846 | 1572 |
Reported symptom on questionnaire among responders | 56.4 | 482 | 364 |
Spirometry conducted in those reporting symptoms | 66.1 | 559 | 287 |
Diagnosed with COPD in those attending spirometry | 39.8 | 87 | 2331 |
Utility | |||
Asymptomatic without COPD15 | 0.8394 | 1522 | 291 |
Symptomatic without COPD15 | 0.7549 | 8817 | 2862 |
Costs (£)12 | Value | α | λ |
Postal questionnaire | 4.01 | 99 | 39 |
Booking and conducting spirometry test | 55.27 | 24 | 0.5 |
Beta distribution: the symbols α and β are parameters that define a beta distribution, which is a continuous probability distribution bounded at the extremes by 0 and 1. The number of successes is α, while failure is β.
Gamma distribution: the symbols α and λ are parameters that define a gamma distribution, which is a continuous discrete distribution bounded at the extremes by 0 and ∞. The mean of the distribution is α(1/λ) and variance is α(1/λ).^{2}
*Age -dependent parameters. Values presented are for individuals aged 50- year-olds.
†Based on clinical opinion, it was considered that incident cases account for 10% of prevalent cases (20%) of respiratory symptoms in the UK population, which was validated using values from Eagan (2002).
‡A longitudinal observational primary care database (Dutch Integrated Primary Care Information) follow-up study. The incidence rate was reported in 1000 person-years, which was then converted to a 1-year probability.
§Cohort study of Danish general population at years 0, 5 and 15 (Copenhagen City Heart Study). Of symptomatic normal at baseline that later developed COPD 15 years later, 72% and 28% had GOLD stages 1 and 2, respectively. This was assumed to be a fixed distribution.