We developed a questionnaire to detect cases of chronic obstructive pulmonary disease (COPD) and compared its reliability with other strategies. In order to develop the new questionnaire (COPD screening questionnaire from Terrassa [EGARPOC]) we used data from an epidemiological study on the prevalence of COPD in smokers and calculated the odds ratio for each variable showing significance for the diagnosis of COPD on regression analysis. For comparison among questionnaires and the portable spirometer COPD-6, a cross-sectional multicenter study was performed. The study included 407 smokers or ex-smokers over the age of 40 years with no known diagnosis of COPD, who completed the different questionnaires (EGARPOC, Respiratory Health Screening Questionnaire, COPD-population screener and 2 questions) and underwent spirometry with the COPD-6. We determined the sensitivity, specificity, positive and negative predictive values (S, Sp, PPV and NPV, respectively) and the area under the receiver operating characteristic ROC curve (AUC ROC) of all the questionnaires and the different COPD-6 cut-offs. The prevalence of COPD was 26.3%. The EGARPOC questionnaire showed an S of 81.8%, an Sp of 70.6%, and an NPV of 91.8%; 73.3% of individuals were correctly classified, and the AUC ROC was 0.841. On comparing the questionnaires by the Chi-square test, the 2-question questionnaire showed the worst discrimination; while with an optimal cut-off of forced expiratory volume in one 1 second (FEV)/FEV of 0.78, the COPD-6 was significantly better than the questionnaires in the detection of COPD. Using a cut-off of FEV/FEV of 0.78 the COPD-6 was found to be the best screening tool for COPD in primary care compared to the questionnaires tested, which did not show differences among them.
Purpose: The best criterion for diagnosing airway obstruction in COPD, fixed ratio (FR: FEV1/FVC<0.7) or lower limit of normality (LLN), remains controversial. We compared the long-term evolution of COPD patients according to the initial obstruction criteria. Patients and Methods: Between 2005 and 2008, we evaluated 1728 subjects over 45 years of age with smoking history, pertaining to a primary care center. A total of 424 patients were obstructive by FR, after a bronchodilator test. Of those, 289 patients met obstruction criteria for both FR and LLN and were considered concordant patients (FR+LLN+), while 135 patients were obstructive by FR but non-obstructive by LLN and were defined as discordant patients (FR+LLN-). Results: Forty-eight patients (11.3%) were lost in follow-up, and 158 died (37.3%). After a median time of 120.4 months (IQR 25-75%: 110.2-128.8), 215 patients were spirometrically reevaluated. The annualized loss of FEV1/FVC was greater in discordant (FR+LLN-) patients [0.54 (0.8) vs 0.82 (0.7); p = 0.008], while 81% became concordant (FR+LLN+) during the follow-up. Hospitalization for COPD exacerbations was more frequent in concordant (FR+LLN+) patients (1.57±3.51 vs 0.77±2.29; p = 0.002). Adjusting for age, concordant (FR+LLN+) patients had greater COPD mortality (HR: 2.97; CI 95%: 1.27-7.3; p = 0.02). Conclusion: LLN seems to be less useful for COPD diagnosis in primary care. Discordant (FR+LLN-) patients lost more FEV1/FVC during their evolution and tended to become concordant. LLN predicted COPD hospitalizations and mortality more poorly.
We appreciate the observations of Prof. Miller and colleagues about our article recently published in the International Journal of COPD. 1 The authors feel that our conclusions are not supported by data, based on two main arguments. The first is that concordant and discordant patients are different. This is obvious, and in fact, extensively detailed in our study. It seems that the authors erroneously suggest that our study is penalized by selection bias since concordant and discordant groups are quite dissimilar. In fact, we just compared two different ways of defining airway obstruction in the same prospective cohort, in a similar approach to that used by Prof. Miller et al in a previous publication. 2 Regrettably, in their study, the lack of longitudinal follow-up prevented drawing valid conclusions about the evolution of the patients. Our data suggest that LLN is usually a more restrictive criterion and may misclassify patients with less severe disease. This explains the differences observed during the follow-up in hospitalizations and the COPD mortality after ageadjustment. Our results and those of several previous articles confirm that some patients classified as non-obstructive and therefore without COPD by LLN in fact present severe exacerbations and COPD mortality during follow-up. 3,4 The second argument is that in patients with advanced COPD, the FEV1/FVC ratio can become artificially increased by premature distal airway closure in the spirometric evaluation of vital capacity with forced spirometry. However, the statement that in our study deterioration of pulmonary function was analyzed by the decline of FEV1/FVC ratio is incorrect. The loss of pulmonary function was measured with FEV1 (see Figure 3). It is true that the annualized FEV1/FVC ratio decreased more in discordant patients during follow-up. Nevertheless, the most relevant data concerning this argument-and not mentioned by the authors of the letter-is that 81% of discordant patients in the initial spirometry became concordant during follow-up. Since the two spirometric measures were performed in a similar manner, the fact that a considerable proportion of initially discordant patients developed obstruction by both criteria during the follow-up suggests that the exclusive use of LLN delayed the diagnosis. In our opinion, this is independent of the premature distal airway closure, which in any case should be similar in the two spirometric measurements. Finally, a few additional considerations. FR and LLN are two ways to artificially divide a continuous variable (FEV1/FVC), and therefore rather than two different diagnostic criteria, FR and LLN represent two different points to dichotomize the
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