Blood pressure for kidney protection has been riding high through the first two rounds of the contest and it is currently on the verge of making it to the Filtered Four. This resulted in an avalanche of criticism as people feel that BP for heart protection was the “right” EBM choice.
Take a look at Hector Madariaga’s Storify summarizing the critics positions.
We asked the Blue Ribbon Panel if they wanted to justify this call. We got two takers.
Number One. Blue Ribbon Panel Member #1, Dr. Anonymous:
After reading the entertaining Tweets criticizing (to put it lightly) BP for the Kidney’s win over BP for the Heart (an upset that rivals Michigan State’s loss to Middle Tennessee?), I thought back on why I voted as I did. By the way, I am told the voting on the panel was 5-2 in favor of the kidney! I must admit I struggled a bit to remember why I was one of the 5. First of all, going into it I just find these large BP CV studies to be boring. I am a nephrologist not a cardiologist. This is not to say I deny their importance, and SPRINT with number to treat to prevent an outcome event being only 61 (that is low as far as these studies go) is impressive and the number of meds needed to achieve the lower BP goal was only one more than the higher goal, suggests it is practical. So then why, oh why?
I voted after reading each section that was supplied by the AJKD blog, I believe in this case written by Dr. Swapnil Hiremath. It really was an excellent presentation of both sides of the argument. Go back and re-read it.
Here are the the two written conclusions:
BP control is the cornerstone of risk reduction in the management of the CKD because in study after study, patients with the lower blood pressure have slower progression to renal failure.
Blood pressure reduction is a laudable goal, and should be pursued diligently and doggedly. It reduces cardiovascular events and mortality. But let us not harbour any illusions that it reduces kidney failure. This does not mean that we should let therapeutic nihilism overcome us when treating CKD patients—blood pressure reduction in these patients does help reduce cardiovascular events—and will keep them alive longer.
SPRINT was not powered for renal events, and most renal studies are not powered for cardiovascular events, but I cannot think of a much worse risk factor for CV disease than progressive renal disease. You prevent renal failure, you prevent death. I am a nephrologist.
Number Two. Blue Ribbon Panel Member #2, Dr. Daniel Weiner*:
SPRINT, ah SPRINT
Even though SPRINT was stopped early, the study is not done. Specifically, there are very few overall kidney outcomes and one would not expect much in this juncture given the known acute interplay between blood pressure and kidney hemodynamics. For CV disease, we are left trying to reconcile SPRINT and ACCORD. While SPRINT shows a reduction, ACCORD does not. People have noted that this may be a result of ACCORD’s factorial design as the HRs for CV outcomes were below 1. However, the really impressive outcome in SPRINT was all-cause mortality as that is not subject to adjudication. In ACCORD, the HR for all-cause mortality was 1.07 (not statistically significant), which is in the opposite direction from that in SPRINT. So where are we now? We have the long-term follow-up of MDRD and AASK, the latter of which only saw a benefit in patients with proteinuria and the former of which showed strong benefit. There also is HALT-PKD, where there was a benefit seen in kidney growth with BP control.
So, for this voter, I am holding out hope for kidney protection with blood pressure control and think it will be a few years before SPRINT will be ready to truly answer this question.
[*Note: Dr. Weiner was the principal investigator at the Boston clinical site in SPRINT.]
Selection committee member Ray Townsend sent a short e-mail on his thoughts:
What if I have a slightly different spin?
EG: Its not just BP reduction, it’s whether someone’s BP falls on meds (achieved reduction) when they have CKD, and on what kind of background (like APOL1)
Here BP “tractability” is a surrogate for good versus bad protoplasm/genes