Stages of disease severity and factors that affect the health status of patients with chronic obstructive pulmonary disease

Background We hypothesized that the factors which may influence health stat us would differ in patients at different disease stages of chronic obstruct ive pulmonary disease (COPD). The present study investigated how impairment s in health status were distributed in male patients at each disease stage according to the British Thoracic Society (BTS) guidelines, and analysed th e contribution of the clinical indices, the dyspnoea rating and the psychol ogical status to the health status of patients at the three disease stages of COPD. Methods: A total of 218 consecutive male patients with stable COPD were rec ruited from our outpatient clinic. All eligible patients completed pulmonar y function testing, progressive cycle ergometry, a dyspnoea rating [Medical Research Council (MRC) dyspnoea scale], an assessment of their anxiety and depression [Hospital Anxiety and Depression Scale (WADS)], and an assessme nt of their health status [the St. George's Respiratory Questionnaire (SGRQ )]. The patients were categorized into three groups: mild COPD with a FEV1 at 60-79% of the predicted value, moderate COPD at 40-59% of the predicted value, and severe COPD at below 40% of the predicted value. Results: Twenty-five patients (11%) had mild COPD, 72 patients (33%) had mo derate COPD, and 121 patients (56%) had severe COPD. Significant difference s were observed for the total score and for three components on the SGRQ am ong patients at the three stages (one-way ANOVA, P<0.05). The scores for th e total SGRQ and for the activity component were significantly higher for p atients with severe COPD than for patients with moderate COPD [Fisher's lea st-significant-difference (LSD) method, P<0.05], and also significantly hig her for moderate COPD patients than for mild COPD patients. The maximal oxy gen uptake ((V) over dot O-2 max) correlated significantly with the total S GRQ score in the mild patients [Pearson's correlation coefficient (r) = -0. 67], but not in the moderate or severe patients. The MRC dyspnoea scale had strong correlations with the SGRQ in all patient groups (r = 0.53 similar or equal to 0.70). Anxiety and depression on the HADS showed moderate corre lations with the SGRQ score in the mild and severe patients (r = 0.51 simil ar or equal to 0.57). Multiple regression analysis showed that in patients with mild COPD, the MRC and (V) over dot O-2 max accounted for the total sc ore on the SGRQ. Anxiety on the HADS plus the MRC scale accounted for the t otal score on the SGRQ in patients with moderate COPD, and anxiety on the H ADS, the MRC scale and the FEV1 significantly influenced the SGRQ severe CO PD patients. Conclusions: The disease staging proposed by the BTS guidelines can separat e patients with COPD according to impairments in their health status. Furth ermore, the factors that influence health status differed in patients at th e: three disease stages. Our findings support the boundaries used in diseas e staging and some recommendations from the BTS guidelines.