Letter by Fung et al Regarding Article, “Frailty and Clinical Outcomes in Heart Failure: A Systematic Review and Meta-analysis”

The following two letters consist of a critique and author's reply related to an article in this month's journal, which was published online early enough to obtain both the letter and reply in time to publish all three simultaneously. The letter by Fung et al raises legitimate questions about the conduct and interpretation of data in a systematic review and meta-analysis, which the response by Zhang et al addresses point-by-point. Taken together, these correspondences illustrate many of the challenges inherent in conducting a comprehensive and valid systematic review and meta-analysis.