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Differences in severe exacerbation frequency across GOLD stages. Red, classic CB+ vs classic CB–; blue, SGRQ CB+ vs SGRQ CB–. Circles represent mean difference and error bars represent 95% CI. *P < .05 and †P < .0001 compared with classic CB– or SGRQ CB–, respectively, on multivariable linear regression. See Figure 1 and 2 legends for expansion of abbreviations.
