Background: The Dyspnoea, Obstruction, Smoking, Exacerbation (DOSE) index was designed to assess disease severity and for the clinical management of chronic obstructive pulmonary disease (COPD), but has not been evaluated as a prognostic instrument for mortality in a population including primary care patients.
Aims: The aim of this study was to investigate the associations of the DOSE index with mortality in primary and secondary care COPD patients.
Methods: Information was collected from 1,111 COPD patients aged 34-75 years randomly selected from 70 Swedish primary and secondary care centres. Data were obtained using patient questionnaires and record review and the Swedish Board of Health and Welfare provided mortality data. The study population included 562 patients with data on all DOSE index components. The DOSE index was calculated using the MRC dyspnoea scale, forced expiratory volume in 1 second (FEV₁) as percentage of predicted (FEV₁%pred), smoking status, and exacerbation rate. The exacerbation rate over 6 months prior to record review was used to estimate the annual rate. Cox regression analyses estimated survival with adjustment for age, sex, and heart disease.
Results: Over 5 years, 116 patients (20.6%) died. Mortality was higher in patients with DOSE index ≥4 (42.4%) than for lower scores (11.0%) (p<0.0001). Compared with a DOSE index score of 0-3, the hazard ratio for mortality was 3.48 (95% CI 2.32 to 5.22) for a score of 4-5, and was 8.00 (95% CI 4.67 to 13.7) for a score of 6-7.
Conclusions: The DOSE index is associated with mortality in COPD patients in primary and secondary care and can be used to assess prognosis in addition to other clinically relevant issues.