By Sarah Guy, medwireNews Reporter
The Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification of chronic obstructive pulmonary disease (COPD) predicts mortality better than the 2011 ABCD scoring system, report Norwegian researchers.
Mortality gradually increased with GOLD grading, but was similar in groups A and B, and in groups C and D of the ABCD system, a 2011 revision of the GOLD grading strategy combining symptom burden and risk for exacerbations.
"Our results indicate that the prognostic information given by the four spirometric GOLD grades should not be neglected when predicting mortality in people with COPD," suggest Linda Leivseth (Norwegian University of Science and Technology, Trondheim) and colleagues.
As reported in Thorax, the team analyzed data for 1540 participants of a 1995-1997 study that included spirometry testing to indicate lung function. A total of 837 (54%) participants died during the 14.6-year follow up.
Participants were categorized according to GOLD criteria, giving a distribution of 28% GOLD 1 (pre- and post-bronchodilator [pp] forced expiratory volume [FEV]1 ≥80), 57% GOLD 2 (50≤ pp FEV1 <80), 13% GOLD 3 (30≤ pp FEV1 <50), and 2% GOLD 4 (pp FEV1 <30).
By contrast, when categorized according to the ABCD system - which uses the same GOLD gradings in addition to a "low" (A and C), or "high" (B and D) symptom burden and exacerbation risk - 61% satisfied group A criteria, 18% group B, 12% group C, and 10% group D.
Mortality rates increased with increasing GOLD categorization, in comparison with GOLD 1, and the rest of the general Norwegian population, report Leivseth et al. For example, female participants graded GOLD 2 were 2.29 times more likely to die, those in GOLD 3 were 6.23 times more likely, and those in GOLD 4 were 6.97 times more likely. Patterns were similar for male study participants.
Notably, mortality rates did not differ dramatically between groups A and B, and between groups C and D, write the authors.
A "likely explanation" may be that pp FEV1 is dichotomized at 50 in the ABCD classification, "resulting in less discrimination between people with different lung function," they add.
Finally, GOLD grading predicted mortality significantly more accurately than did the ABCD grading system, giving significantly higher figures in Chi-squared analysis.
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