I heard a talk today by one of the fellows in our program who is also the senior author on this recent JASN article: Phosphorus Binders and Survival on Dialysis.
Interestingly, even though the current KDOQI Guidelines recommend the use of phosphate binders to maintain serum phosphorus levels within the normal range, there has never been a randomized controlled trial demonstrating the superiority of their use compared to placebo. The FDA approval of phosphate binders is based primarily on their ability to lower serum phosphorus, rather than any hard outcomes such as mortality or cardiovascular disease.
Furthermore, the practice of prescribing phosphate binders is so ingrained in nephrologists, and is considered the standard-of-care based on the current practice guidelines, that it would be considered ethically inappropriate to conduct a phosphate binder-versus-placebo prospective study today.
As such, the authors of the above study looked at a cohort of over 10,000 patients within the Fresenius dialysis system and divided them into two groups, which were followed prospectively: those who were prescribed phosphate binders, and those who were not. Obviously, it is difficult to completely eliminate confounders in a study like this, but the authors attempted to do so by performing a technique known as propensity score matching, in which patients with similar baseline characteristics are matched with one another and those at the extremes (e.g., too healthy, too sick) are excluded from the study. I'm no stat-man myself, but a friend of mine who is claims that propensity score matching is becoming the accepted standard for these types of epidemiologic studies. In any case, the authors of this study found a substantially decreased one-year mortality in patients who were treated with phosphate binders compared to those who were not.