In contrast to our results, Vodicka [43] found no association between comet assay damage index and the XRCC1 (Arg399Gln) and XRCC3 (Thr241Met) polymor-phisms probably due XRCC1 (Arg399Gln) contribute partially to DNA repair capacity and the polymorphisms of other genes could play a role in detecting COPD risk (e.g. XRCC4 genetic polymorphisms which repairs DNA double-strand breaks by non-homologous end joining [NHEJ] and the completion of recombination events) [11]. This evidence concerns the gene XRCC4 and chronic obstructive pulmonary disease.