Table 1

Base case assumptions for model: among ever smokers aged 40–79 years without diagnosis of COPD

Base caseSource/explanation
Proportion of cohort having respiratory symptoms
 Dyspnoea0.32HSE analysis
 MRC grade 3 dyspnoea or worse0.13
 Chronic cough or phlegm0.21
 Any of the above0.48
Proportion having childhood asthma0.04HSE analysis
Proportion with clinically significant COPD* among those with respiratory symptoms0.16HSE analysis
Proportion of COPD* with low FEV1 (% predicted)
 50–79%0.73HSE analysis
Proportion of COPD* with MRC grade 3 dyspnoea or worse0.39HSE analysis
Proportion of COPD* with either FEV1 <50% or MRC grade 3 dyspnoea0.51HSE analysis
Response rate to postal questionnaire/reminders0.5Response rates estimates from previous experience/literature vary between 50% and 90%22 23
Probability that patients consult their GP/staff at least once per year0.91 over 12 monthsPatients 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 opportunistically0.5Reported rates for atrial fibrillation screening with pulse 30–70%23 26
Response rate to questionnaire in surgery0.9Response rates 98–100%11 12 27
Proportion attendance for spirometry0.7Uptake rates 33–97%5 12 23 27
Sensitivity of spirometry test (quality compared with specialised technician)1.0Possible 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.