CHEST Guidelines-Response_chest

Response_chest_17

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In a correspondence published in the journal CHEST, Curtis W. Noonan critiques a 2014 study by Clark et al., which investigated the effects of pleural plaques on lung function among former vermiculite workers exposed to amphibole fibers. Noonan expresses concern over the study's statistical power, suggesting that the study may have lacked sufficient power to reject the null hypothesis, which asserts no significant difference in lung function between the pleural plaques group and the normal CT scan group. Noonan highlights that the study's power ranged from only 15% to 34%, far below the typically acceptable level of 80% needed to confidently avoid type 2 errors (false negatives).<br /><br />In response, Clark and colleagues defend their methodology, stating that their study demonstrated adequate power for certain comparisons, such as between normal CT scan findings and other miner groups, but acknowledged the limitations when comparing the pleural plaques only group. They argue against Noonan's post hoc power analysis, emphasizing that post hoc analyses are generally considered flawed and misleading, as they don't provide meaningful or new insights once statistical insignificance is determined. They maintain that their original conclusion—that pleural plaques alone do not significantly affect lung function—is still valid based on their study design and data.<br /><br />The discourse suggests that while the conclusions of Clark et al.'s study should be interpreted cautiously, especially in light of incomplete exposure assessments, the statistical methods employed were appropriate for the study’s primary objectives. Clark et al. clarify that their study focused on physiological outcomes rather than occupational exposure causality, disputing Noonan’s categorization of it as solely an occupational study. Finally, both sets of correspondence highlight the nuances of statistical interpretation, especially in retrospective studies with inherent limitations.

Keywords

pleural plaques

lung function

vermiculate workers

amphibole fibers

statistical power

type 2 errors

post hoc analysis

occupational study

retrospective studies

CHEST journal