Table 1.
Base case assumptions for model: among ever smokers aged 40–79 years without diagnosis of COPD
| Base case | Source/explanation | |
|---|---|---|
| Proportion of cohort having respiratory symptoms | ||
| Dyspnoea | 0.32 | HSE analysis |
| MRC grade 3 dyspnoea or worse | 0.13 | |
| Wheeze | 0.25 | |
| Chronic cough or phlegm | 0.21 | |
| Any of the above | 0.48 | |
| Proportion having childhood asthma | 0.04 | HSE analysis |
| Proportion with clinically significant COPD* among those with respiratory symptoms |
0.16 | HSE analysis |
| Proportion of COPD* with low FEV1 (% predicted) | ||
| 50–79% | 0.73 | HSE analysis |
| 30–49% | 0.23 | |
| <30% | 0.04 | |
| Proportion of COPD* with MRC grade 3 dyspnoea or worse | 0.39 | HSE analysis |
| Proportion of COPD* with either FEV1 <50% or MRC grade 3 dyspnoea | 0.51 | HSE analysis |
| Response rate to postal questionnaire/reminders | 0.5 | Response rates estimates from previous experience/literature vary between 50% and 90%22 23 |
| Probability that patients consult their GP/staff at least once per year | 0.91 over 12 months |
Patients aged 45–64 years consult on average 3.3 times per year24; patients with COPD consult 6.4 times per year.25 Overall estimate based on Poisson distribution, varying the prevalence of COPD between 1% and 20%. Assume patients will not be questioned more than once per year. |
| Proportion of consultations where questionnaire is administered opportunistically |
0.5 | Reported rates for atrial fibrillation screening with pulse 30–70%23 26 |
| Response rate to questionnaire in surgery | 0.9 | Response rates 98–100%11 12 27 |
| Proportion attendance for spirometry | 0.7 | Uptake rates 33–97%5 12 23 27 |
| Sensitivity of spirometry test (quality compared with specialised technician) | 1.0 | Possible 3% underdiagnosis28 but literature suggests overdiagnosis most common |
*
Clinically significant COPD is defined as respiratory symptoms and airways obstruction (National Institute for Health and Clinical Excellence criteria).
Estimates based on 1 year time period.
COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in 1 s; GP, general practitioner; HSE, Health Survey for England; MRC, Medical Research Council.