In Reply: We agree with Dr Floege and colleagues that our study shows an association between phosphorus levels and all-cause mortality in patients with chronic kidney disease. However, being a meta-analysis of observational studies, it was not designed to determine whether lowering phosphorus reduces mortality, which would require randomized trial data. Such trials have yet to demonstrate such a causal association.
We pooled data from available observational studies that published linear estimates (on a logarithmic scale) of the relative risks of death associated with serum parathyroid hormone. Although some studies indicated possible nonlinear associations between different categories of serum parathyroid hormone and mortality, use of sophisticated methods such as splines to summarize information across studies was not possible because of the small number of published data points generally available. Moreover, visual inspection of the risk of mortality plotted against serum parathyroid hormone levels in Figure 2 did not indicate an increased risk of death with higher parathyroid hormone levels, and this is particularly evident for the graph based on adequately adjusted studies.
Palmer S, Craig J, Strippoli GFM. Mortality in Chronic Kidney Disease and Mineral Metabolism—Reply. JAMA. 2011;306(2):159-160. doi:10.1001/jama.2011.949