Comparison of different staging methods for COPD in predicting outcomes

Abstract

Chronic obstructive pulmonary disease (COPD) is commonly staged according to the percentage of predicted forced expiratory volume in 1 s (FEV1 % pred), but other methods have been proposed. In this study we compared the performance of seven staging methods in predicting outcomes.We retrospectively studied 296 COPD outpatients. For each patient the disease severity was staged by separately applying the following methods: the criteria proposed by the Global Initiative for Chronic Obstructive Lung Disease (GOLD), quartiles of FEV1 % pred and z-score of FEV1, quartiles and specified cut-off points of the ratio of FEV1 over height squared ((FEV1·Ht−2)A and (FEV1·Ht−2)B, respectively), and quartiles of the ratio of FEV1 over height cubed (FEV1·Ht−3) and of FEV1 quotient (FEV1Q). We evaluated the performance of these methods in predicting the risks of severe acute exacerbation and all-cause mortality.Overall, staging based on the reference-independent FEV1Q performed best in predicting the risks of severe acute exacerbation (including frequent exacerbation) and mortality, followed by (FEV1·Ht−2)B. The performance of staging methods could also be influenced by the choice of cut-off values. Future work using large and ethnically diverse populations to refine and validate the cut-off values would enhance the prediction of outcomes.

Mechanisms affecting exercise ventilatory inefficiency-airflow obstruction relationship in male patients with chronic obstructive pulmonary disease

“…Subjects with coexisting heart failure with/ without documented pulmonary embolism, primary valvular heart disease, pulmonary artery hypertension, pericardial disease, exercise-induced angina, ST changes, and severe arrhythmias were also excluded. As few female subjects meet the criteria of COPD in Taiwan [20], they were not included in this study. We also excluded those who had contraindications to perform the exercise test and those who were participating in exercise training.…”

“…Third, all of the participants in this study were male, so the results cannot be applied to females. As only 4% of patients with COPD are female in Taiwan [20], and as breathing pattern and dead space are different between men and women [42], it would be difficult to enroll a sufficient number of female subjects with COPD to compare the differences between male and female patients with COPD. To calculateVE=VCO2S andVE=VCO2I , the methodology to identify VCP or RCP [1,9,29] and whether to use the entire loaded exercise data [5] or data below VCP/RCP [2,3,[11][12][13] are inconsistent in the literature.…”

Assessment of severity and prognosis in COPD: moving beyond percent of predicted

“…Even though most COPD patients die of comorbidities or during an exacerbation well before reaching this minimal level of lung function, the risk of such an outcome would be expected to increase as this index decreases but, interestingly, the FEV1Q has also been shown to correlate with mortality even in a subpopulation having FEV1 within the normal range [12]. The study by HUANG et al [9] confirms the findings of MILLER and PEDERSEN [12] that the FEV1Q correlated better with mortality than two other reference-independent indices proposed earlier, FEV1/height 2 and FEV1/height 3 , and shows in addition that FEV1Q correlated well with three interrelated SAE outcomes. The percent of predicted by quartiles also correlated well with mortality, but not with SAEs, while percent predicted by GOLD correlated less well with both, and z-scores showed a good correlation only to an adjusted model for mortality.…”

“…While the analysis by quartiles has the advantage for this study of allowing like−like comparisons between the methods, the cut-off points that result may not translate to other populations, but do inform the choice of more generic cut-offs. For example, in the clinical COPD population reported by HUANG et al [9], the quartile breaks for FEV1 percent predicted occurred at 69, 53 and 41%, while the GOLD divisions at 80, 50, and 30% placed 81% of the patients in the two mid-levels with only 12% in the highest and 7% in the lowest. Note that because this study defined obstruction by the Global Lung Function 2012 Initiative LLN for FEV1/FVC [13], rather than 0.70, the false-positives usually seen by GOLD would not be included.…”

“…Other indices, based upon the absolute value of FEV1, and thus not dependent upon a reference value, have been proposed but are not yet in wide use. Recently in the European Respiratory Journal, HUANG et al [9] reported an evaluation of seven methods to categorise reductions in FEV1, comparing their correlations to the outcomes of acute exacerbations and mortality. While this study in a Taiwanese population with confirmed COPD was relatively small (n=296) and predominantly male (94%), the results draw attention to some of the less commonly used indices and may cause us to rethink our dependence on percent of predicted.…”