Authors: Tomoyuki Kawada
Publish Date: 2015/11/06
Volume: 51, Issue: 2, Pages: 173-173
Abstract
Nagata et al 1 investigated the effects of protonpump inhibitors PPIs and the effects of their interactions with several drugs including lowdose aspirin with regard to the risk of lower gastrointestinal tract bleeding They conducted a case–control study and the adjusted odds ratios for lower gastrointestinal tract bleeding were estimated by use of a logistic model PPI use did not result in any significant increase in the risk of lower gastrointestinal tract bleeding In addition the adjusted odds ratio of PPI use for lower gastrointestinal tract bleeding did not become significant for any concomitant therapy with nonsteroidal antiinflammatory drugs lowdose aspirin clopidogrel or warfarin I have some queries regarding their studyFirst Miyake et al 2 recently conducted a retrospective cohort study that confirmed the combination of lowdose aspirin and PPIs increased the risk of lower gastrointestinal tract bleeding in patients with ischemic heart disease The adjusted hazard ratio for concomitant use of PPIs was 655 95 confidence interval 201–2132 in 548 patients using lowdose aspirin I suspect that the wide range of the 95 confidence interval was caused by the limited number of patients with lower gastrointestinal tract bleeding n = 18 and the combination of lowdose aspirin and PPIs should be used with caution because of the risk of lower gastrointestinal tract bleeding In addition the study design is different between the two studies and discrepancies in the study outcomes should be confirmed by further studySecond there are two types of logistic regression analysis and conditional logistic regression analysis can be applied to a case–control study with a sufficient number of controls If they conducted individual matching and they used an unconditional logistic model the study outcomes would become conservative estimates Namely no statistical significance can be caused partly by the statistical procedure As Nagata et al had a sufficient number of controls they should have used the appropriate logistic model for their studyFinally there are several causes of lower gastrointestinal tract bleeding and about half of the cases were due to diverticular bleeding I recommend Nagata et al conduct a sensitivity analysis with special reference to the main cause of lower gastrointestinal tract bleeding to simplify the combined effect of PPIs and several drugs including lowdose aspirin As their study cannot guarantee the safety of the combination of PPIs and nonsteroidal antiinflammatory drugs lowdose aspirin clopidogrel or warfarin further study is recommended for patients using PPIs
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