The recently published study by Dell’omo and associates is described as a prospective case-control study; however, this is incorrect. The study participants were selected based on previously untreated type 1, 2, and 3 wet age-related macular degeneration (AMD) and were matched with respect to age. The participants were followed up prospectively to compare the levels of vascular endothelial growth factor. Although AMD is a disease state, the authors’ underlying hypothesis is that AMD affects vascular endothelial growth factor, and in this context of their study, AMD is viewed as a risk factor. As such, their study describes a prospective, age-matched cohort study, not a case-control study. This error has implications for the appropriate statistical analysis, and therefore, the proper interpretation of the observed results. A number of statistical tests are described in the Methods; it is not clear whether those tests that are described have been applied appropriately. For example, it is not clear if the correlations in Table 2 reflect data from a single point in time or over time. If over time, then the Spearman correlations would not be appropriate, because it does not account for clustering. Therefore, Table 2 is either poorly constructed or incorrect. At a minimum, the authors should specify at what time points the correlations were drawn. The authors are strongly urged to conduct a reanalysis of their study data and provide readers with the appropriate measures of association and P values, amending their interpretation as warranted.
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