ELN and chronic obstructive pulmonary disease: However, the presence of IgG binding to elastin in only 43% of the early onset COPD indicates either the existence of other antigen that may be causing the remaining 57% EO-COPD to develop severe emphysema or, considering the disparity of reports in this matter [6]–[9], it is possible that a abridged sensibility of the tests and/or divergent COPD variants tested may cause dispersion in the results.