Is platelet dose really the whole answer?

Is platelet dose really the whole answer?

Over the last few years, platelet dose has become one of the most debated topics in PRP research.

Some authors have gone as far as suggesting that approximately 10 billion platelets or even more may represent the "correct dose" for achieving long-term clinical efficacy.

After reviewing very carefully the original data from several key studies, I am not convinced the answer is that simple…

Let's compare two frequently cited trials (RCTs):

𝗕𝗮𝗻𝘀𝗮𝗹 𝗲𝘁 𝗮𝗹. (2021)

• 84% Kellgren-Lawrence grade III OA 

• PRP dose: 10.45 billion platelets

𝗣𝗮𝘁𝗲𝗹 𝗲𝘁 𝗮𝗹. (2024)

• 80% Kellgren-Lawrence grade II OA 

• PRP dose: 2.82-5.65 billion platelets

At first glance, the discussion usually focuses on platelet dose.

But look at the patient populations and baseline characteristics below:

Extracted from both articles

One study treated predominantly KL III patients with substantially worse baseline symptoms, while the other focused on much younger patients with earlier disease stage.

These are not the same clinical phenotype.

This raises an uncomfortable question:

𝗔𝗿𝗲 𝘄𝗲 𝘀𝘂𝗿𝗲 𝘄𝗲 𝗮𝗿𝗲 𝗺𝗲𝗮𝘀𝘂𝗿𝗶𝗻𝗴 𝘁𝗵𝗲 𝗲𝗳𝗳𝗲𝗰𝘁 𝗼𝗳 𝗱𝗼𝘀𝗲... 𝗮𝗻𝗱 𝗻𝗼𝘁 𝘁𝗵𝗲 𝗲𝗳𝗳𝗲𝗰𝘁 𝗼𝗳 𝗽𝗮𝘁𝗶𝗲𝗻𝘁 𝘀𝗲𝗹𝗲𝗰𝘁𝗶𝗼𝗻?

Even more interesting, the study by Bansal and collaborators is often cited as evidence that 10 billion platelets are "critical" for long-term efficacy.

However, when examining the WOMAC and IKDC curves, a different picture emerges.

The clinical response peaks during the first months after injection and progressively declines thereafter.

At 12 months, patients remain “statistically” better than the HA group, but much of the initial improvement has been lost almost completely (compared to baseline). See below.

Figure 2a, Bansal et al., 2021 Scientific Reports

This does not necessarily invalidate the treatment.

But it certainly challenges the narrative that a single injection containing 10 billion platelets provides a durable long-term solution. Are they really reaching MCID after 12 months? 

Perhaps the real question is not:

"What is the optimal platelet dose?"

But rather:

"What is the optimal platelet dose for a specific patient phenotype, disease stage, PRP composition and treatment strategy?"

According to Patel´s study and reported data on 2024, a dose of 5 billion platelets demonstrates some clinical benefit (much better on pain subscales), at least up to 6 months and for knee OA grade II relatively young patients…

Figure 3, Patel et al., 2024 Orthopaedic Journal of Sports Medicine

In my opinion, and i am just trying to understand and interpret the published literature, platelet dose is only one variable among many:

• OA severity • Baseline PROMs • Age • Number of injections • Injection route • Leukocyte content and specific types • Red blood cell contamination • PRP volume • Follow-up duration

As our field matures, I believe that we really need to move beyond simplistic dose-based conclusions and start analysing PRP as the complex biological therapy that it actually is.

What is your view?

Do you believe the platelet dose is the key determinant of efficacy, or are we still underestimating the importance of patient phenotype and PRP full formulation? Should the dose be tailored according to disease stage and injection route?

Disclaimer: I have no doubt that platelet dose matters... but it is only one piece of a much larger puzzle.

Sources:

https://pmc.ncbi.nlm.nih.gov/articles/PMC10896053/

https://pmc.ncbi.nlm.nih.gov/articles/PMC7889864/