IJCA-18461; No of Pages 2 International Journal of Cardiology xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Letter to the Editor
FGF23 and risk of all-cause mortality and cardiovascular events: A meta-analysis of prospective cohort studies Karl Krupp, Purnima Madhivanan ⁎ Robert Stempel College of Public Health & Social Work, Florida International University, Miami, USA
a r t i c l e
i n f o
Article history: Received 6 June 2014 Accepted 27 July 2014 Available online xxxx Keywords: Cardiovascular disease Cohort studies Fibroblast growth factor 23 Meta-analysis
Dear Editor, We read Xiao et al.'s article on “Fibroblast growth factor 23 and risk of all-cause mortality and Cardiovascular events: A meta-analysis of prospective cohort studies” published in the April 2014 issue of the International Journal of Cardiology with great interest [1]. The topic is both important and timely; FGF23 has recently emerged as an important focal point for research on cardiovascular risk and mortality. A review and meta-analysis helps to summarize the state of current knowledge and highlight areas requiring further research. Unfortunately, while well written, this article falls short of the standards we would expect for reviews of this type as the authors have failed to synthesize the available research into a coherent body of evidence that can inform practice. First, while Xiao and colleagues say they have complied with the MOOSE guidelines for Meta-Analyses and Systematic Reviews of Observational Studies, there is little evidence that these procedures were actually used [2]. For instance, in the text the authors say they have conducted a systematic review of the literature; but they give no reasonable explanation why they would exclude data from cohort studies such as the Framingham Heart Study, the Heart and Soul Study, and the Northern Manhattan Study. These are some of
⁎ Corresponding author at: Department of Epidemiology, Robert Stempel College of Public Health & Social Work, Florida International University, Miami 11200 SW 8 Street, HLS 390W2, Miami, FL 33199, USA. Tel.: +1 305 348 4907; fax: +1 305 348 4901. E-mail address: pmadhiva@fiu.edu (P. Madhivanan).
the largest and most methodologically sound research studies available, so excluding them without an explanation seems arbitrary and unreasonable. Conducting a review with only one database also has potential to compromise the validity of results [3]. Authors should use several databases like Cochrane, EMBASE, or CENTRAL to minimize this risk [4,5]. Searching a single source, according to Lemeshow and colleagues, reduces sensitivity to as low as 66% [3]. A recent comparison of Pubmed and Google Scholar by Shariff and colleagues for instance found that Google Scholar's retrieval rate was double that of PubMed with a similar precision (PubMed: 11%; Google Scholar: 22%; P b 0.001) [6]. We performed a search of EMBASE using the search strategy employed by the authors and identified a number of additional prospective studies that might have been eligible for the review (citations available upon request). There is also no evidence that the authors have assessed the quality of studies included in the meta-analysis. This is of critical importance in interpreting the review's conclusions. According to the Cochrane Review Handbook, quality assessment is required to “gain insight into potential comparisons, and guide interpretation of findings” and “reduce bias” [7]. According to Cochrane, any factor related to applicability of findings, validity of individual studies, and design characteristics that might affect interpretation of results should be evaluated for rigor and generalizability. The research community has gone to great lengths to improve the quality of reporting of systematic reviews and meta-analyses through the development of the PRISMA statement [4]. This study lacks several important features that are mandatory according to PRISMA. For instance, search strings used for the study are not included making it impossible to replicate the review. The lack of an abstract also seriously undermines the ability of researchers to assess whether a future review might duplicate Xiao et al.'s work. While authors say they have evaluated included research on “key indicators of study quality”, they have not shared the results of those assessments with their readers. In addition, the authors fail to talk about the strengths and limitations of their review; there is no discussion of reasons why some of the larger studies have non-significant findings; and we are unable to assess whether findings are generalizable to other populations. In summary, we applaud the authors for a well written, if flawed, review. We complement them on the thoughtfulness of their analytical methods; however the manuscript would have been much strengthened if they had given as much thought to their inclusion criteria and discussion of the strengths and limitations of the studies they were analyzing. Clinical decision-making has benefited enormously from the availability of high quality systematic reviews and meta-analyses.
http://dx.doi.org/10.1016/j.ijcard.2014.07.142 0167-5273/© 2014 Elsevier Ireland Ltd. All rights reserved.
Please cite this article as: Krupp K, Madhivanan P, FGF23 and risk of all-cause mortality and cardiovascular events: A meta-analysis of prospective cohort studies, Int J Cardiol (2014), http://dx.doi.org/10.1016/j.ijcard.2014.07.142
2
K. Krupp, P. Madhivanan / International Journal of Cardiology xxx (2014) xxx–xxx
Unfortunately, as evidenced by this manuscript, sometimes those findings are not organized in a manner that would assist clinicians or researchers. Following guidelines from organizations like Cochrane, Campbell Collaboration, and others would have resulted in a more substantial contribution to the field. Funding/support None. Conflicts of interest None. Ethical review Not applicable.
References [1] Xiao Y, Luo X, Huang W, Zhang J, Peng C. Fibroblast growth factor 23 and risk of all-cause mortality and cardiovascular events: a meta-analysis of prospective cohort studies. Int J Cardiol 2014 Jul 1;174(3):824–8. http://dx.doi.org/10.1016/j.ijcard. 2014.04.138 [Electronic publication ahead of print 2014 Apr 22]. [2] Stroup DF, Berlin JA, Morton SC, et al. Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis of observational studies in epidemiology (MOOSE) group. JAMA 2000;283:2008–12. [3] Lemeshow AR, Blum RE, Berlin JA, Stoto MA, Colditz GA. Searching one or two databases was insufficient for meta-analysis of observational studies. J Clin Epidemiol 2005;58:867–73. [4] Liberati A, Altman DG, Tetzlaff J, et al. The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. PLoS Med 2009;6:e1000100. [5] Shariff SZ, Sontrop JM, Iansavichus AV, et al. Availability of renal literature in six bibliographic databases. Clin Kidney J 2012;5:610–7. [6] Shariff SZ, Bejaimal SA, Sontrop JM, et al. Retrieving clinical evidence: a comparison of PubMed and Google Scholar for quick clinical searches. J Med Internet Res 2013;15: e164. [7] Higgins JPT, Green S e. Cochrane handbook for systematic reviews of interventions version 5.1.0. [updated March 2011] The Cochrane Collaboration; 2011 [Available from http://www.cochrane-handbook.org].
Statement of authorship All authors have contributed to the critical revision of the manuscript for important intellectual content.
Please cite this article as: Krupp K, Madhivanan P, FGF23 and risk of all-cause mortality and cardiovascular events: A meta-analysis of prospective cohort studies, Int J Cardiol (2014), http://dx.doi.org/10.1016/j.ijcard.2014.07.142
Contents lists available at ScienceDirect
International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Letter to the Editor
FGF23 and risk of all-cause mortality and cardiovascular events: A meta-analysis of prospective cohort studies Karl Krupp, Purnima Madhivanan ⁎ Robert Stempel College of Public Health & Social Work, Florida International University, Miami, USA
a r t i c l e
i n f o
Article history: Received 6 June 2014 Accepted 27 July 2014 Available online xxxx Keywords: Cardiovascular disease Cohort studies Fibroblast growth factor 23 Meta-analysis
Dear Editor, We read Xiao et al.'s article on “Fibroblast growth factor 23 and risk of all-cause mortality and Cardiovascular events: A meta-analysis of prospective cohort studies” published in the April 2014 issue of the International Journal of Cardiology with great interest [1]. The topic is both important and timely; FGF23 has recently emerged as an important focal point for research on cardiovascular risk and mortality. A review and meta-analysis helps to summarize the state of current knowledge and highlight areas requiring further research. Unfortunately, while well written, this article falls short of the standards we would expect for reviews of this type as the authors have failed to synthesize the available research into a coherent body of evidence that can inform practice. First, while Xiao and colleagues say they have complied with the MOOSE guidelines for Meta-Analyses and Systematic Reviews of Observational Studies, there is little evidence that these procedures were actually used [2]. For instance, in the text the authors say they have conducted a systematic review of the literature; but they give no reasonable explanation why they would exclude data from cohort studies such as the Framingham Heart Study, the Heart and Soul Study, and the Northern Manhattan Study. These are some of
⁎ Corresponding author at: Department of Epidemiology, Robert Stempel College of Public Health & Social Work, Florida International University, Miami 11200 SW 8 Street, HLS 390W2, Miami, FL 33199, USA. Tel.: +1 305 348 4907; fax: +1 305 348 4901. E-mail address: pmadhiva@fiu.edu (P. Madhivanan).
the largest and most methodologically sound research studies available, so excluding them without an explanation seems arbitrary and unreasonable. Conducting a review with only one database also has potential to compromise the validity of results [3]. Authors should use several databases like Cochrane, EMBASE, or CENTRAL to minimize this risk [4,5]. Searching a single source, according to Lemeshow and colleagues, reduces sensitivity to as low as 66% [3]. A recent comparison of Pubmed and Google Scholar by Shariff and colleagues for instance found that Google Scholar's retrieval rate was double that of PubMed with a similar precision (PubMed: 11%; Google Scholar: 22%; P b 0.001) [6]. We performed a search of EMBASE using the search strategy employed by the authors and identified a number of additional prospective studies that might have been eligible for the review (citations available upon request). There is also no evidence that the authors have assessed the quality of studies included in the meta-analysis. This is of critical importance in interpreting the review's conclusions. According to the Cochrane Review Handbook, quality assessment is required to “gain insight into potential comparisons, and guide interpretation of findings” and “reduce bias” [7]. According to Cochrane, any factor related to applicability of findings, validity of individual studies, and design characteristics that might affect interpretation of results should be evaluated for rigor and generalizability. The research community has gone to great lengths to improve the quality of reporting of systematic reviews and meta-analyses through the development of the PRISMA statement [4]. This study lacks several important features that are mandatory according to PRISMA. For instance, search strings used for the study are not included making it impossible to replicate the review. The lack of an abstract also seriously undermines the ability of researchers to assess whether a future review might duplicate Xiao et al.'s work. While authors say they have evaluated included research on “key indicators of study quality”, they have not shared the results of those assessments with their readers. In addition, the authors fail to talk about the strengths and limitations of their review; there is no discussion of reasons why some of the larger studies have non-significant findings; and we are unable to assess whether findings are generalizable to other populations. In summary, we applaud the authors for a well written, if flawed, review. We complement them on the thoughtfulness of their analytical methods; however the manuscript would have been much strengthened if they had given as much thought to their inclusion criteria and discussion of the strengths and limitations of the studies they were analyzing. Clinical decision-making has benefited enormously from the availability of high quality systematic reviews and meta-analyses.
http://dx.doi.org/10.1016/j.ijcard.2014.07.142 0167-5273/© 2014 Elsevier Ireland Ltd. All rights reserved.
Please cite this article as: Krupp K, Madhivanan P, FGF23 and risk of all-cause mortality and cardiovascular events: A meta-analysis of prospective cohort studies, Int J Cardiol (2014), http://dx.doi.org/10.1016/j.ijcard.2014.07.142
2
K. Krupp, P. Madhivanan / International Journal of Cardiology xxx (2014) xxx–xxx
Unfortunately, as evidenced by this manuscript, sometimes those findings are not organized in a manner that would assist clinicians or researchers. Following guidelines from organizations like Cochrane, Campbell Collaboration, and others would have resulted in a more substantial contribution to the field. Funding/support None. Conflicts of interest None. Ethical review Not applicable.
References [1] Xiao Y, Luo X, Huang W, Zhang J, Peng C. Fibroblast growth factor 23 and risk of all-cause mortality and cardiovascular events: a meta-analysis of prospective cohort studies. Int J Cardiol 2014 Jul 1;174(3):824–8. http://dx.doi.org/10.1016/j.ijcard. 2014.04.138 [Electronic publication ahead of print 2014 Apr 22]. [2] Stroup DF, Berlin JA, Morton SC, et al. Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis of observational studies in epidemiology (MOOSE) group. JAMA 2000;283:2008–12. [3] Lemeshow AR, Blum RE, Berlin JA, Stoto MA, Colditz GA. Searching one or two databases was insufficient for meta-analysis of observational studies. J Clin Epidemiol 2005;58:867–73. [4] Liberati A, Altman DG, Tetzlaff J, et al. The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. PLoS Med 2009;6:e1000100. [5] Shariff SZ, Sontrop JM, Iansavichus AV, et al. Availability of renal literature in six bibliographic databases. Clin Kidney J 2012;5:610–7. [6] Shariff SZ, Bejaimal SA, Sontrop JM, et al. Retrieving clinical evidence: a comparison of PubMed and Google Scholar for quick clinical searches. J Med Internet Res 2013;15: e164. [7] Higgins JPT, Green S e. Cochrane handbook for systematic reviews of interventions version 5.1.0. [updated March 2011] The Cochrane Collaboration; 2011 [Available from http://www.cochrane-handbook.org].
Statement of authorship All authors have contributed to the critical revision of the manuscript for important intellectual content.
Please cite this article as: Krupp K, Madhivanan P, FGF23 and risk of all-cause mortality and cardiovascular events: A meta-analysis of prospective cohort studies, Int J Cardiol (2014), http://dx.doi.org/10.1016/j.ijcard.2014.07.142
