Poorly Conceived Meta-analysis on Blood Products and Achilles Tendinopathy
POSTED ON IN Foot and Ankle BY Christopher Centeno
One of the most important data-analysis tools we have in evidence-based medicine is called a meta-analysis. However, just like other studies, these can be either well or poorly constructed, which impacts the conclusions. I'd like to introduce you to the dumbest meta-analysis I have ever seen on the use of blood products to treat Achilles tendinopathy, and in the process, maybe we can all learn something about research and PRP.
What Is a Meta-analysis and Why Should You Care?
You may know that medicine is big on research. That research can be everything from writing up a case report to looking at the results of many patients (case series) to conducting a controlled trial. The highest level of evidence that a treatment works or doesn't work is called a placebo randomized controlled trial (RCT). This looks at the efficacy of a treatment by randomizing patients either to get the therapy or a placebo. However, sometimes the results of these RCTs can be conflicting, with one saying that the treatment works and the other reporting that it isn't effective. In that case, doctors rely on what's called a meta-analysis. A meta-analysis usually pools the results of all of the patients from different studies and looks at them as one single data set as if all of the studies had been conducted as one. It then reanalyzes the data to try to break the tie. This, of course, only works if the studies used the same therapy and treated the same diagnosis in the same way. If all of that's not the case, then the meta-analysis is pretty worthless.
Autologous Blood Products
Most of the research to date that uses blood taken from the same patient (autologous) to treat various aches and pains has been using platelet-rich plasma (PRP). This is when the doctor concentrates the platelets in whole blood. However, a few studies have also been performed using whole blood or platelet-poor plasma (PPP). What most patients don't realize is that there are stark differences between the types of PRP being used. Some have red and white blood cells and are called "leukocyte rich" (this PRP appears red and is abbreviated "LR-PRP"). Some have few red and white blood cells and appear amber in color, and this type of product is called "leukocyte poor," or "LP-PRP." In addition, the concentration is different between the kits that doctors often use to make these products. This can range from as low as 1.5 times more platelets than whole blood to as high as 5–7 times (what I call 1.5X–7X). In fact, you can get the platelet concentration even higher if you don't use a simple bedside centrifuge and instead use a state-of-the-art lab, like we do at Regenexx. Please watch my video below on the unique PRP we use:
These different autologous blood products from whole blood to PPP to PRP have dramatically different impacts on tendon cells. In addition, so do the different types of PRP, LR versus LP. Finally, increasing the platelet concentration also has dramatically different impacts on cells. Hence, whole blood, PPP, and the different types of PRP are not at all equivalent. To better understand the different ways that different concentrations or PRP can impact tendon cells, take some time to watch my video below:
The Newest Dumb Meta-analysis
A meta-analysis contains some complex mathematical techniques that are over the head of most physicians, so like any subject over anyone's pay grade, it all looks sophisticated and thus is assumed to be correct. However, the old adage of "garbage in, garbage out" still applies. This is the case with the new meta-analysis. The researchers studied "autologous blood products" and their effects on Achilles tendinopathy. This means these were patients who had pain in their Achilles tendons that was thought due to small tears and swelling in the structure. Rather than aggregating the data from all of the PRP studies that used equivalent products (for example one kit that produced 5X LR-PRP), they pooled all of the PRP studies. In addition, they also threw in all of the whole-blood studies as well. They would have thrown in the PPP research, too, but they didn't find any. After all of this, they concluded that PRP injections for Achilles tendinopathy didn't work. Hence, it doesn't take a rocket scientist to see why this study was garbage in, garbage out. They took vastly different treatments that dramatically impact tendon cells in drastically different ways and assumed they were all the same. That's like studying strep throat and using data from studies that featured five different types of antibiotics, three of which are known to cure strep throat and two that aren't. Despite these drugs being different, when you pool all of this data, the aggregate looks like antibiotics are ineffective for treating strep throat.
Research Showing that PRP Can Heal Achilles Tendons
We've seen many patients through the years with Achilles tendon issues and have effectively treated these patients with precise, ultrasound-guided, high-dose LP-PRP injections. In fact, below is an image of before and after ultrasound images in a case where the surgeons didn't want to touch this woman's macerated and fragile Achilles. In addition, don't take my word for it; a recent study went so far as to biopsy Achilles tendons after PRP treatment and found dramatic improvements in tissue quality as well as improved symptoms. The upshot? My concern with this study is that policymakers who don't understand the differences in blood products that I've described above won't look at this new meta-analysis critically. They may not understand why it's a garbage study. In the meantime, now you understand a little about how a meta-analysis works and also how different PRP treatment preps can impact healing in different ways!
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