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Khagendra Dahal, MD; Juyong Lee, MD, PhD
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FINANCIAL/NONFINANCIAL DISCLOSURES: See earlier cited article for author conflicts of interest.

aDepartment of Medicine, Division of Cardiology, Louisiana State University Health Science Center, Shreveport, LA

bPat and Jim Calhoun Cardiovascular Center, University of Connecticut Health Center, Farmington, CT

CORRESPONDENCE TO: Khagendra Dahal, MD, 1501 Kings Hwy, Shreveport, LA 71104


Copyright 2016, American College of Chest Physicians. All Rights Reserved.


Chest. 2016;150(4):981-982. doi:10.1016/j.chest.2016.07.022
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In a letter to the editor by Meuwese et al regarding our recent paper, they mentioned two important known biases of observational studies, that is, confounding and survival biases. Because of those and other biases, the results of any meta-analysis of observational studies need cautious interpretation. The meta-analyses of randomized trials have been considered to provide robust and, at times, contradictory results in comparison with the meta-analyses of observational studies. However, in the absence of randomized trials to address the question being asked, meta-analyses of observational studies have been long performed, understanding that there may be limitations. At times, the meta-analyses of observational studies provide crucial answers to the questions being asked, as the randomized trials may have restrictive inclusion/exclusion criteria and a limited duration of follow-up. They also provide real-world data.

To improve the quality of the meta-analysis, we performed several subgroup analyses, as mentioned in the paper, and used standard meta-analytic techniques., In addition, the results from our meta-analysis are consistent with the meta-analyses that were restricted to patients on dialysis.

We thank Meuwese et al for raising important concerns.

References

Dahal K. .Kunwar S. .Rijal J. .et al Stroke, major bleeding, and mortality outcomes in warfarin users with atrial fibrillation and chronic kidney disease: a meta-analysis of observational studies. Chest. 2016;149:951-959 [PubMed]journal. [CrossRef] [PubMed]
 
Egger M. .Schneider M. . Davey Smith G. Spurious precision? Meta-analysis of observational studies. BMJ. 1998;316:140-144 [PubMed]journal. [CrossRef] [PubMed]
 
Wells GA, Shea B, O'Connell D, et al. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses.http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp. Accessed July 15, 2016.
 
Stroup D.F. .Berlin J.A. .Morton S.C. .et al Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis of Observational Studies in Epidemiology (MOOSE) group. JAMA. 2000;283:2008-2012 [PubMed]journal. [CrossRef] [PubMed]
 
Lee M. .Saver J.L. .Hong K.S. .et al Warfarin use and risk of stroke in patients with atrial fibrillation undergoing hemodialysis: a meta-analysis. Medicine (Baltimore). 2016;95:e2741- [PubMed]journal. [CrossRef] [PubMed]
 

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References

Dahal K. .Kunwar S. .Rijal J. .et al Stroke, major bleeding, and mortality outcomes in warfarin users with atrial fibrillation and chronic kidney disease: a meta-analysis of observational studies. Chest. 2016;149:951-959 [PubMed]journal. [CrossRef] [PubMed]
 
Egger M. .Schneider M. . Davey Smith G. Spurious precision? Meta-analysis of observational studies. BMJ. 1998;316:140-144 [PubMed]journal. [CrossRef] [PubMed]
 
Wells GA, Shea B, O'Connell D, et al. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses.http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp. Accessed July 15, 2016.
 
Stroup D.F. .Berlin J.A. .Morton S.C. .et al Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis of Observational Studies in Epidemiology (MOOSE) group. JAMA. 2000;283:2008-2012 [PubMed]journal. [CrossRef] [PubMed]
 
Lee M. .Saver J.L. .Hong K.S. .et al Warfarin use and risk of stroke in patients with atrial fibrillation undergoing hemodialysis: a meta-analysis. Medicine (Baltimore). 2016;95:e2741- [PubMed]journal. [CrossRef] [PubMed]
 
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